• TABLE OF CONTENTS
HIDE
 Title Page
 Acknowledgement
 Table of Contents
 List of Tables
 List of Figures
 Abstract
 Introduction
 Literature review
 Towards an appropriate strategy...
 The effect of severe feed restriction...
 Characterizing the onset of sexual...
 Economic analysis of severe feed...
 Summary and conclusions
 Reference
 Biographical sketch






Title: Bio-economic analysis of selected broiler breeder management practices
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 Material Information
Title: Bio-economic analysis of selected broiler breeder management practices
Physical Description: xiii, 172 leaves : ill. ; 29 cm.
Language: English
Creator: Fattori, Thomas Richard, 1950-
Publication Date: 1989
 Subjects
Subject: Dissertations, Academic -- Animal Science -- UF
Animal Science thesis Ph. D
Genre: bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Thesis: Thesis (Ph. D.)--University of Florida, 1989.
Bibliography: Includes bibliographical references (leaves 160-170).
Statement of Responsibility: by Thomas Richard Fattori.
General Note: Typescript.
General Note: Vita.
Funding: Electronic resources created as part of a prototype UF Institutional Repository and Faculty Papers project by the University of Florida.
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Bibliographic ID: UF00056223
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
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Resource Identifier: aleph - 001561953
oclc - 22687645
notis - AHH5653

Table of Contents
    Title Page
        Page i
    Acknowledgement
        Page ii
        Page iii
    Table of Contents
        Page iv
        Page v
    List of Tables
        Page vi
        Page vii
        Page viii
    List of Figures
        Page ix
        Page x
        Page xi
    Abstract
        Page xii
        Page xiii
    Introduction
        Page 1
        Page 2
        Problematic situation
            Page 3
        Researchable problems
            Page 4
        Hypotheses
            Page 5
        Experimental objectives
            Page 6
            Page 7
            Page 8
        Relevance to farming systems research and extension
            Page 9
    Literature review
        Page 10
        Introduction
            Page 10
        Weighing programs
            Page 11
            Page 12
            Page 13
            Page 14
            Page 15
            Page 16
            Page 17
            Page 18
            Page 19
        Pullet rearing period
            Page 20
            Page 21
            Page 22
            Page 23
            Page 24
        Pullet-layer transition period
            Page 25
            Page 26
            Page 27
            Page 28
            Page 29
            Page 30
            Page 31
            Page 32
        Breeder hen laying period
            Page 33
            Page 34
            Page 35
            Page 36
            Page 37
            Page 38
            Page 39
            Page 40
    Towards an appropriate strategy for weighing broilers, broiler breeder pullets and breeder hens
        Page 41
        Introduction
            Page 41
            Page 42
        Materials and methods
            Page 43
            Page 44
            Page 45
            Page 46
        Results and discussion
            Page 47
            Page 48
            Page 49
            Page 50
            Page 51
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            Page 60
            Page 61
            Page 62
            Page 63
            Page 64
            Page 65
    The effect of severe feed restriction during the rearing period on female broiler breeder reproductive performance
        Page 66
        Introduction
            Page 66
            Page 67
        Materials and methods
            Page 68
            Page 69
            Page 70
            Page 71
        Results and discussion
            Page 72
            Page 73
            Page 74
            Page 75
            Page 76
            Page 77
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            Page 86
            Page 87
            Page 88
            Page 89
            Page 90
            Page 91
    Characterizing the onset of sexual maturity in feed restricted broiler breeder females
        Page 92
        Introduction
            Page 92
            Page 93
        Materials and methods
            Page 94
            Page 95
        Results and discussion
            Page 96
            Page 97
            Page 98
            Page 99
            Page 100
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            Page 111
            Page 112
            Page 113
            Page 114
            Page 115
            Page 116
    Economic analysis of severe feed restriction on broiler breeder pullet rearing and breeder hatching egg production
        Page 117
        Subdivision Level 1
            Page 117
            Page 118
            Page 119
        Material and methods
            Page 120
            Page 121
            Page 122
            Page 123
            Page 124
        Results and discussion
            Page 125
            Page 126
            Page 127
            Page 128
            Page 129
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            Page 142
            Page 143
            Page 144
            Page 145
            Page 146
            Page 147
            Page 148
            Page 149
    Summary and conclusions
        Page 150
        Weighing programs
            Page 151
            Page 152
        Feeding programs
            Page 153
            Page 154
        Targeting sexual maturity
            Page 155
            Page 156
        Economic analysis of feeding programs
            Page 157
            Page 158
            Page 159
    Reference
        Page 160
        Page 161
        Page 162
        Page 163
        Page 164
        Page 165
        Page 166
        Page 167
        Page 168
        Page 169
        Page 170
    Biographical sketch
        Page 171
        Page 172
Full Text












BIO-ECONOMIC ANALYSIS OF SELECTED
BROILER BREEDER MANAGEMENT PRACTICES

















BY


THOMAS RICHARD FATTORI


A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY


UNIVERSITY OF FLORIDA


1989

















ACKNOWLEDGMENTS


The author wishes to express his most sincere

appreciation to his co-advisors, Dr. Henry R. Wilson and Dr.

Peter E. Hildebrand, for their guidance throughout the

author's Doctor of Philosophy program. Their strong

direction and support of the selected coursework and

research program enabled an understanding of a broad range

of issues important to poultry management.

Special appreciation is extended to other committee

members, Dr. Steve A. Ford, Dr. R. H. Harms, and Dr. F. Ben

Mather, for their encouragement, technical advisement and

guidance throughout the research program.

Additional gratitude is extended to the professors of

the University of Florida Poultry Science Department, Mr.

David P. Eberst, Mr. W. Gary Smith and the farm crew, and

all members of the staff for their assistance in faciliting

the work load over a long research period.

The author is also indebted to Mr. Harold Barnes and

Gold Kist, Inc. for the cooperation and assistance in

conducting research on-farm and whose advice was of great

value.











Sincere appreciation is expressed to the author's

parents, Mr. and Mrs. L. A. Fattori, for their support and

personal encouragement throughout the graduate program.

The author wishes to extend his deepest appreciation to

his wife Maisha for her care and support of their home and

family which freed the many hours needed to complete this

program. Without her patient understanding this endeavor

would have never been completed.


iii



















TABLE OF CONTENTS


Page

ACKNOWLEDGMENTS ................ ................... ii

LIST OF TABLES........................................ vi

LIST OF FIGURES..................................... ix

ABSTRACT.................. ............................. Xii

CHAPTERS

I INTRODUCTION.................................. 1

Problematic Situation ..................... 3
Researchable Problems...................... 4
Hypotheses.................... ................ 5
Experimental Objectives..................... 6
Relevance to Farming Systems Research
and Extension.............................. 9

II LITERATURE REVIEW........................ 10

Introduction ............................. 10
Weighing Programs.......................... 11
Pullet Rearing Period....................... 20
Pullet-Layer Transition Period............. 25
Breeder Hen Laying Period ................... 33

III TOWARDS AN APPROPRIATE STRATEGY
FOR WEIGHING BROILERS, BROILER BREEDER
PULLETS AND BREEDER HENS.................... 41

Introduction.......................... ..... 41
Materials and Methods....................... 43
Results and Discussion........................... 47

IV THE EFFECT OF SEVERE FEED RESTRICTION
DURING THE REARING PERIOD ON FEMALE
BROILER BREEDER REPRODUCTIVE PERFORMANCE.... 66













Introduction................................ 66
Materials and Methods..................... 68
Results and Discussion........... .......... 72

V CHARACTERIZING THE ONSET OF SEXUAL MATURITY
IN FEED RESTRICTED BROILER BREEDER FEMALES.. 92

Introduction..., ..... ......... ..... .. 92
Materials and Methods..................... 94
Results and Discussion ...................... 96

VI ECONOMIC ANALYSIS OF SEVERE FEED
RESTRICTION ON BROILER BREEDER PULLET
REARING AND BREEDER HATCHING EGG PRODUCTION. 117

Introduction ............*................ 117
Materials and Methods..................... 120
Results and Discussion.................... 125

VII SUMMARY AND CONCLUSIONS., ............. .... 150

Weighing Programs........................... 151
Feeding Programs ...................... ... 153
Targeting Sexual Maturity................... 155
Economic Analysis of Feeding Programs....... 157

REFERENCES........... ......... ........ ............ 160

BIOGRAPHICAL SKETCH......... .... ...*.. ..... ...**....** 171

















LIST OF TABLES


Table Pafe

3-1 Effect of feeding time (ERL vs. LTE) and time
of day on non-laying broiler breeder female
mean body weight and weight change (Exp. 1)...... 56

3-2 Effect of scale type (ELC vs. SPR) and sample
units (IND vs. GRP), on mean adult breeder hen
and breeder pullet body weight and uniformity
(SD), (Exp. 2) ................................... 57

3-3 Effect of sample location (FDD vs. END) and
sample type (PND vs. FXD) on mean straight-run
broiler body weight and uniformity (SD),
(Exp. 3)................................. ....... .58

3-4 Effect of sample location (FDD vs. END) at
various ages and by sample type (PND vs. FXD)
on mean pullet body weight and uniformity (SD),
(Exp. 3) ......................................... 59

3-5 Effect of sample location (FDD vs. END) at
various ages and by sample type (PND vs FXD) on
mean breeder hen body weight and uniformity (SD),
(Exp. 3) ....................... .................. 60

3-6 Effect of sample location (FDD vs. END) on mean
breeder hen and pullet body weight gain (Exp. 3). 61

3-7 Classification of suspect outliers as true
outliers by testing mean body weight with an
outlier interval ( 3*SD) for broilers, pullets
and breeder hens (Exp. 3)........................ 62

3-8 Effect of sample size on mean and variance of
body weight for broilers, pullets and breeder
hens.............................................. 63

4-1 Composition, calculated nutrient content and age
used for the starter and grower diets............ 80

4-2 Daily nutrient intake of broiler breeders after
20 weeks of age.................................. 81











4-3 Effect of feed treatment on growth, development
and mortality of breeder hens.................... 82

4-4 Effect of feed treatment on breeder hen mean
( SEM) production performance................... 83

4-5 Effect of feed treatment on hen-day production
for chronological and physiological ages......... 84

4-6 Effect of feed treatment on mean ( SEM)
specific gravity (SG) and egg weight (EW), and
the correlation between these parameters at
various ages...................................... 85

4-7 Effect of feed treatment on mean ( SEM)
hatchability of all eggs set (Hatch) and
fertility (Fert) at various ages................. 86

4-8 Cumulative feed, crude protein and metabolizable
energy intake per bird at various chronological
and physiological ages and by feed treatment..... 87

5-1 Correlation coefficient (r) and the significance
probability that the correlation is zero (P>/r/)
for various physical attributes associated with
sexual maturity................................. 101

5-2 Effect of feed treatment (mean + SEM) on various
physical attributes associated with sexual
maturity......................................... 103

5-3 Effect of feed treatment on bursa weight (mean +
SEM) and relative proportion of bursa and fat pad
to body weight................................... 105

5-4 Effect of feed treatment (mean + SEM) on various
physical attributes associated with sexual
maturity.......................................... 106

6-1 Base costs, production coefficients and + 20%
adjustments used in sensitivity analysis of a
pullet rearing enterprise........................ 135

6-2 Base costs, production coefficients and + 20%
adjustments used in sensitivity analysis of a
breeder hen laying enterprise.................... 136

6-3 Average total cost of a pullet survivor reared
to a common age by feeding program.............. 137


vii











6-4 Effect of feeding program on pullet rearing
average cost budget through 5% production,
calculated at base prices....................... 138

6-5 Effect of feeding program on breeder hen average
cost budget through 40 weeks of production,
calculated at base prices and expressed as
dollars per survivor............................. 139

6-6 Effect of feeding program on breeder hen average
cost budget through 40 weeks of production,
calculated at base prices and expressed as
dollars per dozen hatching eggs................. 140

6-7 Average total cost of a dozen hatching eggs
produced to a common age by feeding program,
calculated at base prices and before salvage
adjustments.......................... .......... 141

6-8 Live body weight (kg) by feeding program at
various transfer (laying house) ages and the
relative difference (%) among programs........... 142


viii

















LIST OF FIGURES


Figure Page

3-1 Effect of early feeding schedule and time of
weighing on broiler breeder female body
weight (Exp. 1)............................. ..... 64

3-2 Cyclic changes in non-laying breeder female body
weight, on an early or late feeding schedule..... 64

3-3 Frequency distribution of confidence intervals
for a fixed quantity of birds excluding outliers
(A) and all birds in a penned-up group (B)....... 65

4-1 Average weekly high (HI) and low (LO)
temperatures and hours of daylight (LIGHT)
during the research period....................... 88

4-2 Live body weight from hatching to 62 weeks of
age as affected by feed treatment................ 88

4-3 Relationship between body weight (Y, g) and age
(X, d) as affected by feed treatment at 50%
production (flock maturity)..................... 89

4-4 Effect of feed treatment on hen-day
production (%).................................. 90

4-5 Hen-day production of double-yolked eggs (%) as
affected by feed treatment..................... 91

4-6 Mean egg weight (g) and specific gravity (g/mL)
plotted over the production period for the STD
and -24% feed treatments....................... 91

5-1 Effect of feed treatment on shank length (mm)
with respect to age (wk) and body weight (g)..... 107

5-2 Effect of feed treatment on fat pad weight (g)
with respect to age (wk) and body weight (g)..... 108

5-3 Effect of feed treatment on pubic spread or arch
(cm) with respect to age (wk) and body
weight (g)................... ... ........ ... ..... 109











5-4 Effect of feed treatment on head score (no.,
5=most developed) with respect to age (wk) and
body weight (g).................................. 110

5-5 Effect of feed treatment on comb factor (cm-2)
with respect to age (wk) and body weight (g)..... 111

5-6 Effect of feed treatment on plasma total lipid
(mg/mL) with respect to age (wk) and
body weight (g) ........................ ........ 112

5-7 Effect of feed treatment on oviduct weight (g)
with respect to age (wk) and body weight (g)..... 113

5-8 Effect of feed treatment on ovary weight (g)
with respect to age (wk) and body weight (g)..... 114

5-9 Relationship of mean bursa.weight (g) to body
weight (g) as affected by feed treatment
(TRT A=+8%, B=STD, C=-8%, D=-16%, and E=-24%).... 115

5-10 Effect of feed treatment on shank length (mm)
with age (wk).................................. .. 116

6-1 Average cost structure of a standard pullet
rearing program, at base prices.................. 143

6-2 Average cumulative feed cost for various
pullet feeding programs.......................... 143

6-3 Sensitivity of pullet average total cost to
changes in component costs at 20, 25, and 30
weeks of age for the STD feeding program
(CHK=chick, PFD=pullet feed, PPAY=grower pay,
PMRT=pullet mortality, DENSITY=pullet housing
density)............. .................... .... ..... 144

6-4 Sensitivity of pullet average total cost to
changes in component costs at 20, 25, and 30
weeks of age for the -24% feeding program......... 145

6-5 Effect of a 20% change in component costs on
average total cost per pullet survivor at 5%
production........................................ 146

6-6 Average total cost of a dozen hatching eggs for
the STD and -24% feeding programs, with age...... 146











6-7 Sensitivity of breeder hen average total cost
to changes in feed costs (BFD) or costs due to
breeder hen mortality (BMRT) at 40 weeks of
production and for the STD or -24% feeding
programs ............... ........................ 147

6-8 Sensitivity of breeder hen average total cost
to changes in pullet depreciation costs (PUL$) or
costs due to breeder hen mortality (BMRT) at 40
weeks of production for the STD and -24%
feeding programs................................. 148

6-9 Effect of changes in pullet housing density on
average total cost per pullet (ATC/P) at 5%
production .................... ................. 149

6-10 Effect of adjusted pullet housing density on
average total cost of a dozen hatching eggs
(ATC/E) on a STD and -24% feeding program, with
age.............................................. 149
















Abstract of Dissertation Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Doctor of Philosophy

BIO-ECONOMIC ANALYSIS OF SELECTED
BROILER BREEDER MANAGEMENT PRACTICES

BY

THOMAS RICHARD FATTORI

December, 1989

Chairman: Henry R. Wilson
Cochairman: Peter E. Hildebrand
Major Department: Animal Science (Poultry Science)


Studies were conducted to evaluate bird weighing

procedures and the effect of selected broiler breeder

management practices on pullet and breeder hen growth and

reproductive performance.

Evaluations were made of the effects of sample and

batch size, in-house locations, type of scale, time of

weighing and procedure complexity used in the on-farm

weighing of broiler breeder stock on body weight gain and

uniformity. Time of weighing was shown to be an important

source of error when estimating live weight gain. No

significant differences in average body weight due to scale

type or batch size could be detected. A significant

location effect was found with breeder hens, but not with

broilers or breeder pullets. It was determined that

suspected outliers should not be rejected from the sample.


xii











The effect of quantitative feed restriction on breeder

hen reproductive performance was determined. Proportional

decreases in feed allocation below standard practices

resulted in corresponding decreases in body weight, double-

yolked eggs and number of days in production to 64 weeks.

Egg weight, fertility, hatchability, and female mortality to

64 wk of age were not significantly affected by feed

treatment. A delay in sexual maturity caused a significant

decrease in average hen-day production to 64 wk, but not in

total settable eggs per hen-housed.

The effects of feed restriction on attributes

associated with sexual maturity (comb, bursa, fat pad,

plasma lipid, ovary, oviduct, and shank), were

characterized. The main effect was a delay in the

development of these attributes without significantly

altering their ultimate physiological values, with the

exception of shank length which was permanently reduced by

severe feed restriction.

The economic effect of severe feed restriction on

pullet rearing and breeder hen cost structures was analyzed.

Average pullet rearing cost was increased by ca. 3% when

feed restriction delayed maturity by 3 weeks. The resulting

increased pullet depreciation cost was not offset in the

laying period until ca. 67 wk of age. Projected average

total costs beyond 67 wk were lower for severe restriction

than standard feeding practices, especially if pullet

housing density is adjusted to an equivalent bio-mass.


xiii

















CHAPTER I

INTRODUCTION


The Joint Council on Food and Agricultural Sciences has

developed national research priorities in the area of animal

production for a number of years. In 1988 the general area

of reproductive efficiency was targeted as a fiscal priority

for research, extension and higher education (Cook, 1988).

Cook noted that this topic was particularly important to the

broiler industry where growth rates and reproduction are

negatively correlated. The Joint Council suggested that

priority be given to research goals which develop

technologies and educational programs that increase the

efficiency and profitability of broiler breeder

reproduction. The goals of this dissertation conform well

with those identified by the Joint Council. Furthermore,

this research endeavor has targeted the broiler breeder

manager as its principal client and attempts to demonstrate

how research findings can be applied to direct field use.

Perhaps the most significant change in the broiler meat

industry over the last ten years was the transition from a

production-driven to a market-driven industry. As American

consumers increased their demand for value, convenience,













quality and nutrition from the food market place, broiler

meat producers competed actively to fulfill these needs.

Evidence of industry's ability to respond effectively to

this dynamic consumer behavior is the fact that total per

capital consumption of poultry meat increased consistently

over this time period. Also, consumer demand drove further

processed poultry products into all segments of the market

place. Now, over 6,000 specialty products using chicken and

other poultry are marketed by the poultry industry and

further enhancement of this wide product line to meet the

diverse wants of the consumer is expected to continue

(Brown, 1989).

This change to a consumer orientation may seem distant

from the main issue of this dissertation, but it has had a

direct affect on broiler breeder reproductive efficiency and

management practices. Primary breeder companies, those that

market broiler breeder parent stock to the broiler industry,

have shifted their selection emphasis to those phenotypic

traits with the greatest bio-economic importance. For

example, emphasis on selection for increased egg numbers and

hatchability of parent stock lowers growth and feed

efficiency performance in the broiler progeny. Conversely,

emphasis on growth rate in the progeny will lower

reproductive performance in the breeder house. The relative

economic importance of parental reproductive traits such as

egg production, hatchability, livability or breeder feed













conversion are not as great as such progeny traits as yield

(with its associated characteristics, including grade and

conformation), feed conversion and growth rate in today

market environment (Rishell, NA). A percentage change in

processing yield will have a greater effect on profits than

will an equal change in any of the other genetic traits

considered in a breeding program.


Problematic Situation

Different breeding policies among the various primary

breeders result in strains of birds that are suited for

different market conditions. This genetic variability can

be used to an advantage by broiler producers so that a

flexible production response to consumer demand can be

achieved. In fact it is not uncommon for a production
complex to utilize several commercial breeds at the same

time. The problematic situation being that each strain of

bird is best managed by a specific set of procedures.

A successful broiler breeder management program is one

that optimizes the use of feed, labor, capital and other

resources in the production of placeable chicks per hen

housed. The complexity of this challenge is made evident by

the depth and diversity of possible factors that can impact

either negatively or positively on the production process.

Management must account for and control variation in

the growth and development of a particular strain of broiler














breeder caused by differences in the physical and manageria.
environments in which they are reared and bred. Those

managers who approach breeder reproductive performance from

a life cycle perspective will find that maintaining the

proper balance between controlled growth and reproduction is

an easier task than those who do not.



Researchable Problems
The primary objective of a broiler breeder management

program is to carefully monitor and control each phase of

growth and development during the life cycle, Breeder

managers are required to constantly make decisions

concerning feed formulation and allocation based on body

weight information generated from a pullet weighing program

or body weight and egg production information in the breeder

hen program. Inaccurate information will result in

inefficient and sometimes costly decisions--costly to the

integrator (increased chick cost), hatching egg producer

(lower payments) and society as a whole (higher meat cost)

as resources are not used efficiently.

The researchable problems identified in this

dissertation relate to this decision making process on the

part of the breeder manager. Specifically, the researchable

problems arise from the breeder managers need to 1)

establish an effective body weight monitoring and control

program, 2) maximize the number of placeable chicks from a














breeder rearing and laying program, 3) target sexual

maturity, and 4) optimize economic returns from pullet

rearing and breeder hen laying programs.



Hypotheses

Hypothesis 1

If procedures for the on-farm weighing of broilers,

broiler breeder pullets and breeder hens can be optimized

with respect to the total time (cost) required to conduct

the weighing program, then monetary returns to the growers,

breeders and integrator will increase. Increased returns

will result from more efficient use of labor and feed

resources, as well as increased breeder reproductive

performance.



Hypothesis 2

If the appropriate broiler breeder body weight growth

curve resulting from a level of feed restriction can be

identified, then reproductive performance placeablee chicks)

of a housed flock can be maximized.



Hypothesis 3

If changes in the physical characteristics of a breeder

hen that signal the onset of sexual maturity as she passes

through the pullet-layer transition period can be identified

for various degrees of severe feed restriction, then these













traits can be utilized to alert the breeder manager to

ensuing increases in nutritional needs of the flock.



Hypothesis 4

If broiler breeders are severely feed restricted during

the rearing period and the resulting biological response is

an equivalent but delayed reproductive performance relative

to standard practices then, economic returns to the pullet

grower, hatching egg producer and broiler integrator from

restricted feeding will be increased above levels derived

from recommended practices.



Experimental Objectives



Regarding Hypothesis 1

The experimental objectives regarding hypothesis 1 were

to: 1. quantify the cyclic change in body weight over a 48

hour period;

2. illustrate the potential error in estimating weight

gain when weighing are not conducted at the same time each

weighing;

3. determine the effect of scale type, sample units,

sample size, sample location, time of sampling and

complexity of the procedures used in the on-farm weighing of

broilers, broiler breeder pullets and breeder hens, on

average body weight, body weight gain and uniformity;













and 4. determine the effect of subjectively removing

suspected outliers from a sample group on average body

weight estimates and uniformity.



Regarding Hypothesis 2

The experimental objectives regarding hypothesis 2 were

to: 1. evaluate the broiler pullet growth response to

various degrees of severe feed restriction;

2. evaluate the breeder hen growth and production

response to various degrees of severe feed restriction;

3. evaluate changes in reproductive physiology related

to severe feed restriction;

4. evaluate the effect of severe feed restriction on

hatching egg characteristics;

and 5. evaluate breeder hen technical efficiencies related

to feed usage and production performance.



Regarding Hypothesis 3

The experimental objectives regarding hypothesis 3 were

to: 1. quantify the effect of severe feed restriction on

various physical attributes associated with sexual maturity

through the pullet-layer transition period;

2. assess the degree of linear correlation among all

quantified physical attributes at various ages;













3. characterize in graphic form the age and body

weight relationships to changes in the various physical

attributes;

and 4. relate findings from the characterization process

to possible field applications.



Regarding Hypothesis 4

The experimental objectives regarding hypothesis 4 were

to: 1. examine the effect of severe feed restriction on

pullet rearing cost structure;

2. determine the cost of delayed sexual maturity due

to various levels of severe feed restriction;

3. test the sensitivity of the average total cost of

rearing a pullet to 5% production to changes in component

costs;

4. examine the effect of severe feed restriction on

breeder hen cost structure;

5. compare breeder hen average total costs on a

survivor and per dozen hatching eggs basis;

6. test the sensitivity of average total cost of

breeder hen hatching egg production to changes in component

costs;

7. estimate the changes in pullet rearing cost

structure due to changes in pullet housing density;

and 8. estimate the changes in breeder hen laying cost

structure to changes in pullet housing density.













Relevance to Farming Systems Research and Extension

The strength of the Farming Systems Research and

Extension (FSR/E) approach to technology generation is

derived, in part, from its systems perspective while

accounting for the biological as well as the socio-economic

factors that impact on the production process. The

vertically integrated broiler production systems of today

are highly complex by agricultural standards and economies

of scale are required in their competitive marketplace. In

such a system, savings of a hundredth of a cent per pound of

product from increased technical efficiencies can translate

into millions of dollars of added net income for growers,

breeders and integrator.

Therefore, FSR/E methodology is perhaps the most

appropriate approach to technology generation at the breeder

level in that it prescribes a complete socio-economic, as

well as biological, analysis of the production system. The

methodology utilized in this research drew upon

multidisciplinary issues that ranged from information

systems to the physiological aspects of sexual maturity. The

result is a dissertation that is more comprehensive than

would have been attained if "traditional" procedures were

followed. Furthermore, client participation in problem

identification and diagnoses was sought out, and diffusion

of research findings back to the client was achieved in a

workshop setting.

















CHAPTER II

LITERATURE REVIEW



Introduction

Information in the literature on various broiler

breeder management practices is relatively scarce. Even

more surprising is the paucity of scientific research on

such fundamental issues as weighing programs, bird and flock

behavior, and economic analysis of production. This is

unfortunate because managing today's broiler breeder is a

complex practice that requires knowledge of the bird and the

broad range of factors affecting it.

A review of the current literature reveals that two

basic perspectives have been taken by researchers, one

nutritional, the other physiological. The nutritional

studies have focused on feeding programs and the nutritional

requirements of the bird, whereas the physiological studies

have focused on lighting programs and the physiological

requirements for the initiation of sexual maturity. Both

perspectives are interrelated and are better understood if

examined under a common forum.

It is important to identify from the start a few of the

principal causes of variation and conflicting findings in

















CHAPTER II

LITERATURE REVIEW



Introduction

Information in the literature on various broiler

breeder management practices is relatively scarce. Even

more surprising is the paucity of scientific research on

such fundamental issues as weighing programs, bird and flock

behavior, and economic analysis of production. This is

unfortunate because managing today's broiler breeder is a

complex practice that requires knowledge of the bird and the

broad range of factors affecting it.

A review of the current literature reveals that two

basic perspectives have been taken by researchers, one

nutritional, the other physiological. The nutritional

studies have focused on feeding programs and the nutritional

requirements of the bird, whereas the physiological studies

have focused on lighting programs and the physiological

requirements for the initiation of sexual maturity. Both

perspectives are interrelated and are better understood if

examined under a common forum.

It is important to identify from the start a few of the

principal causes of variation and conflicting findings in













the literature. Environmental effects such as photoperiod,

temperature, humidity, and air and litter quality have a

strong influence on maintenance, growth and production.

Pullet management can interact with breeder management,

especially when birds are moved into new housing for

production. Differences in breeder strain, housing,

equipment, feed ingredients, and feed and water quality can

all be a source of variation in commercial performance as

well as experimental discrepancy or error.

This review will examine the following areas of

interest: weighing programs and pullet rearing, pullet-layer

transition, and breeder hen laying periods.



Weighing Programs

Weighing Methodology

A review of the current broiler breeder management

guides revealed a broad range of recommended sample weighing

techniques. Recommendations ranged from no suggested

methodology at all (Hubbard Farms, 1988-89, and Avian Farms

International, 1989) to extensive procedures by Ross Poultry

Breeders, Inc., (1986). The weighing techniques recommended

by Ross include individually weighing every bird in a

penned-up group (ca. 50 to 100 birds) every week from 4 wk

of age through peak production.

Generally, most primary breeders recommend that birds

be individually weighed weekly, starting at 4 or 5 wk of age














and continued through peak production. All birds in a
penned-up group should be weighed and the weighing should

consistently occur on the off-feed day, at the same time

(afternoon) and at the same locations in the house.

Variation in the number of locations to use in a house range

from 2 to 5 depending upon the company. For example,

Peterson Farms (1988) recommends weighing a minimum of 2% of

the females and 5% of the males each week from 3 wk through

peak production, every two weeks up to 48 wk of age and

monthly thereafter. They suggest group weighing from 3
through 4 wk of age and then individual weighing from 5 wk

on. Sampling should be random and as consistent as

possible. Weigh all birds penned from 4-5 locations in the

house on the off-feed days. Weigh at the same time each

weighing and use the same scale.

The only recent publication found on weighing

methodology was by Harms et_ l. (1984b). This study was

conducted to develop a method for weighing egg-type pullets

that would be faster, more accurate, and more informative

than previous procedures. They concluded that weighing

replacement pullets in groups of 5 was just as good as

weighing individual birds. The average weight was the same

if all birds penned were weighed. They utilized a 95%

confidence limit to determine whether the birds differed

significantly from a desired target body weight. They also

used the bird-to-bird standard deviation to provide a














mathematical value to compare the variation from flock to

flock. The use of sample variance in testing sample

adequacy when weighing broilers was also demonstrated by

Jaap (1955). Jaap recommended weighing ca. 25 birds from 3

locations in a house to estimate the average weight of a

flock of broilers.

Sources of Variation

Lilburn et_ al. (1987) reported that breeder pullets fed

every day were significantly heavier at each age measured

than those fed every other day, even though mean cumulative

feed intake was not significantly different between

restriction treatments. -They noted that part of this extra

body weight in the every-day treatment could be the result

of feed in the crop at the time of weighing. A more recent

publication (Bennett and Leeson, 1989b) comparing skip-a-day

and daily feeding programs, also noted that time of weighing

and feed retention in the digestive tract can strongly

influence the interpretation of growth trials with broiler

breeders.

Meal feeding in broilers was shown to increase

variability of body weights resulting from increased

variability in quantity of crop contents (May et al., 1988,

and Vergara et al., 1989). This finding was shown to be

complicated further by environmental temperature: lower

temperatures increased feed intake and variability in crop

content.













Feed restriction influences total water intake as well
as the cyclic patterns of water consumption (Bennett and

Leeson, 1989a). These researchers reported that boredom and

hunger were not the main stimuli of the cyclic pattern of

water consumption associated with feeding programs; they

concluded that the meal on the on-feed day had a much

stronger influence on water consumption than hunger or

boredom on the off-feed day. Quantities of water consumed

can also be affected by diet ingredients. Patterson et al.

(1989) demonstrated that water intake can be increased by as

much as 1.5 times when feeding high fiber ingredients (wheat

middlings) as compared to a lower fiber corn-soy diet. They

also reported that the form of feed can influence water

intake and showed that pelleted feed will increase water

intake over mash. Birds fed high fiber diets tend to eat

more feed to achieve an equivalent intake of energy than

birds on a low fiber diet. This suggests that it is both the

quantity of feed as well as the fiber content that leads to

increased water intake.

Water consumption is also influenced by the strain of

bird used in production (Ogunji et al., 1983). These

researchers reported significant differences in water intake

for two breeder male strains known to exhibit differences in

loose droppings. They also demonstrated that dietary

protein had no significant influence on water consumption.

However, fecal moisture increased as dietary protein













increased. Water consumption significantly increased as

dietary salt increased on feed days, but dietary salt did

not influence water consumption on the off-feed days.

Inherent differences in water consumption among strains of

breeders make water, litter and weighing management a

difficult task.

Feed and water management is also influenced by bird

behavior, which in turn can contribute to problems for the

weighing program. Murphy and Preston (1988) found that the

duration of eating and drinking among individuals was

variable.

Appleby et al. (1985) reported on a breeder hen

movement (ranging) study involving commercial flocks of ca.

4000 broiler breeders housed in deep litter. The study was

conducted intensively from 22 to 33 wk of age and then at

monthly intervals until 55 wk of age. They found that

closely restricted ranges did not occur in either sex.

Males had slightly larger ranges than females, but not

significantly so. There was no consistent change in the

area of the house used with age, and nesting was widely

distributed throughout the house. These findings were in

agreement with Craig and Guhl (1969) who reported that

individuals in flocks of chickens do not use space evenly

and that home ranges are either ill-defined or non-existent.














Electronic Weighing Systems

Efficient poultry production requires accurate

information and statistics that enable decision makers to

act in a timely manner. This is especially true for

monitoring and controlling growth and development of almost

every class of poultry. An ideal weighing program would

supply accurate day to day information on growth and

uniformity at a reasonable cost. A variety of electronic

microprocessor-based scales are currently available for

almost every poultry production system and offer the

potential to fulfill these needs.

Lott et al, (1982) and Stutz et al. (1984) described

the development and application of an automated weighing and

analysis system for growth and efficiency studies. They

noted that the prime advantages of such a system were in the

reduction of transcription errors and labor requirements

compared to conventional methods. Feighner et al. (1986)

reported that the implementation of a computerized weighing

system resulted in a 60 to 65% savings in time over manual

acquisition and use of a calculator to analyze the data.

The portability of the micro-computer nade it possible to

transport to remote research and production areas.

Meltzer and Landsberg (1988) described the process of

recursive (continual up-dating) calculations and flexibility

of modern data loggers in collecting and analyzing body

weight data. Briefly, a weighing sensor (load cell)














transfers the value of a momentary load of a bird standing

on it into a computerized weight indicator. The hardware

contains a set of adaptive, time-varying filters used to

detect exact weights of a moving, live load. Also, it can

differentiate between, and adjust for, weights caused by

debris left on the platform by establishing previously

defined tolerance limits. The tolerance definitions are

based on the known standard deviations of a normal flock

plus a margin of safety. Each weighing is recorded either

as an in- or out-of-range weight and is placed in its proper

distribution. Pooled in-range weights are subjected to

statistical processing for average and standard deviation

calculations. The calculations are recursive, so that

average and standard deviations are up-dated on each

weighing and all output, including a distribution table and

histogram, are printed on demand.

The reliability of an automatic weighing system is

limited by accuracy of readings and numbers of birds using

the scale. Turner et al. (1983) found there was good

agreement between automatic and manual weighing when a

perch-type platform was used. Their results showed no bias

by the frequent use of the perch by certain individuals to

the exclusion of others. There was, however, an indication

that broilers used the perch less frequently with increasing

age. Newberry et al. (1985) conducted a study with roasters

kept to 10 wk of age to evaluate this effect. Mean body














weights obtained on the automatic weighing system were

significantly lower at 7 and 10 wk of age than those

obtained manually. They attributed this result to the

larger birds at later ages perching with part of their

weight in contact with the floor and recommended raising the

perch higher with age. Birds observed on the weighing perch

on one day of the week were 3.5 times more likely to use the

perch again on the following two days. Perching rate

decreased from 41.6 birds/h in wk 1 to 4.3 birds/h in wk 10.

Blockhuis et al. (1988) reported that in broiler trials

comparing manual to automatic weighing systems, the

automatic (platform scale) gave a consistently lower value

than weighing by hand. The difference becoming greater as

the birds aged from 4 to 6 wk. A study on the behavioral

response to the electronic scales made with both male and

female broilers, showed that the percentage of the tagged

birds that made use of the scales and the average frequency

of use of the scale differed significantly with age and sex.

The average frequency of use of the scale was higher for

females especially at 6 wk of age. This would explain the

lower average weights generated by the automatic weighing

system. A possible explanation for this behavior would be

the relatively lower activity of the heavier males. Between

flocks there was considerable variability in the behavior of

the flocks towards the weighing system. Those flocks that

demonstrated higher male activity had average weights from












19
the electronic scale closer to the manual estimates for body

weight and uniformity.

A recent study on filial and sexual imprinting in

precocial birds (Lavie, 1988) showed that broiler chicks

raised on a commercial farm can be attached to and follow an

imprinting stimuli during the rearing period. Chicks were

subjected to a 3 wk imprinting process from day of age. The

stimulus was comprised of plastic boxes containing a music

cassette that was turned on for 10 minutes every 40 minutes

through 3 wk of age in the brood area of a house. After 3

wk the boxes were placed over the full length of the house

drawing imprinted birds to their new location. Relocation

for the imprinted birds was significantly better than

controls. This report confirmed results of an earlier study

by Gvaryahu et al. (1987) who demonstrated that meat strain

chicks can be attracted to an imprinting stimulus, and the

imprinting object could then be used to move birds from a

training area to a new location. More recently Gvaryahu et

al. (1989) reported that filial imprinting results in

reduced stress behavior and improvements in growth

performance in male chicks. The implication here is the

potential use of imprinting behavior on the automatic

weighing systems. Blockhuis et al. (1988) began their study

at 4 wk of age with no attempt at familiarizing the birds

with the new scales.














Pullet Rearing Period
Mortality

Lee et al. (1971) cited 63 experiments out of 80 where

higher mortality was associated with feed restriction during

the rearing period, and most of the increase was due to

coccidiosis. Since restricted birds are known to increase

litter intake (Harms et al., 1984a) and water intake

(Patterson, 1989) it is not surprising that levels of

mortality due to coccidiosis would be higher. However, Pym

and Dillon (1974) noted that when coccidiosis is well

managed, restriction levels of 60 to 80% of ad libitum

appeared not to have a detrimental effect on rearing

mortality. These researchers also showed that heat stress

mortality for birds fed ad libitum was significantly higher

than for restricted fed birds. They observed that during

the heat stress period the more severely restricted birds

moved around more freely and drank much more water than

birds fed ad libitum.

Mortality levels for pullets reared on 12, 14, 16 and

18% protein diets were not significantly different for

broiler breeders (Summers et al., 1967). This was in

contrast to findings by Bullock et al. (1963) and Blair,

(1972) who found increased mortality among pullets fed even

lower protein (10%) grower diets.














Behavior

Although feed restriction programs are currently

considered essential to ensure acceptable levels of

livability, fertility and hatchability, feed restriction

itself can cause marked behavioral and physiological changes

in growing birds. These effects can have a negative impact

on flock performance. Mench and Shea (1988) found that male

broiler chicks placed on a skip-a-day feeding program were

more aggressive than males fed ad libitum. This display of

aggression manifested more on the off-feed days than on the

feed days. Competition for food is generally considered a

strong stimulus for aggressive behavior. Aggressive

behavior (pecking activity) was shown to be age related with

peak aggression displayed between 9 and 10 wk of age. The

intensity of aggressive behavior shifted from higher levels

on off-feed days to higher levels on feed days by 24 wk of

age.

Van Krey and Weaver (1988) showed that broiler breeder

pullets provided only 45% of the recommended feeder space

responded in terms of growth and uniformity as well as, or

better than, those given 90% of the recommended feeder

space. They noted that all semblance of social order

disappears during the period of frenetic feeding immediately

after food is made available. As a result, all birds are

able to consume at least some feed despite very limited

feeder space.












22

Studies undertaken to compare the growth and uniformity

of birds reared under skip-a-day and daily feeding programs

(Bennett and Leeson, 1989b) showed that body composition and

flock uniformity were unaffected by feeding program. Daily

feeding increased body weight gain indicating that feed is

more efficiently utilized under this feeding program. Those

researchers as well as Lilburn (1986) noted more aggressive

feeding behavior when birds were fed daily.

Comparison trials evaluating a skip-a-day with a skip-

two-days feeding program (Bartov et al., 1988) found that

body weights of birds on the skip-two-days program were

significantly less, but maintained significantly better

levels of uniformity than birds fed on a skip-a-day program.

The decrease in body weight was also associated with a

significant delay in the onset of production, however, no

differences in production to 35 wk of age was detected.

uniformity

The importance of flock uniformity is underscored in

nearly every broiler breeder management guide and poultry

production book available to producers, uniformity is

usually measured as the percent of the birds that weigh

within 10% of the average flock weight (North, 1984).

Acceptable uniformity is when 80% of the birds are in that

weight range. Relatively poor uniformity can result in a

production cycle that is characterized as having a slow

increase to peak production, never reaching a high peak














production, with the peak period being long and the

persistency of production acceptable (Costa, 1981). In a

non-uniform flock, small under-developed birds start laying

much later than larger, heavier birds. This results from a

relatively large spread in age at sexual maturity between

early and late layers where individual birds reach maximum

production at very different ages and a high peak is never

achieved.

Petitte et al. (1981) reported that increased

uniformity of broiler breeders could be achieved by

segregation according to body weight accompanied by feeding
different protein levels to each weight category. Flock

uniformity measured at 20 wk of age increased from 80 to 89%

by utilizing this management procedure. A more recent study

with non-segregated body weight groupings by Wilson and Dale

(1989) showed that accelerated levels of feed intake (163

g/bird/d) did not improve uniformity when compared to birds

fed at the control level of 150 g/bird/d. Each body weight

group within the flock distribution remained distinct

throughout the study, This suggests that uniformity of

pullet flocks at later ages can only be improved by

segregation and feeding according to body weight groupings.

Housing systems

Deep litter production systems in combination with

slatted platforms are widely used for broiler breeding stock

to produce fertile hatching eggs by natural mating. One












24
alternative to this system for breeders is the use of cages,
which necessitates the labor-intensive practice of

artificial insemination. If breeder females are to be kept

in cages, appropriate feeding and body weight control

programs need to be developed. McDaniel (1974) showed that

broiler breeder hens generally produce more eggs when kept

in cages. However, Fuquay and Renden (1980) reported that

hens maintained in floor pens produced more eggs per day

than hens kept in cages. In their experiment caged females

had significantly higher body weights and significantly

greater variation (less uniformity) in body weights than

floor-reared females. Caged birds generally exhibited

equivalent fertility and hatchability through 59 wk of age,

although they also had higher levels of mortality than floor

birds.

Petitte et al. (1982) reported that caged breeder hens

had significantly heavier body weight and egg weight as

compared to floor birds. Neither mortality nor cumulative

production showed any difference between housing method;

however, during the peak production period the caged hens

exhibited significantly higher levels of production.

A follow-up study by Petitte et al. (1983) showed that

the fertility of the artificially inseminated caged breeders

was significantly lower than that of the naturally mated

birds. Hatchability of eggs at 26 wk was not affected by

housing method; however, hatchability of eggs set at 36 and












25
54 weeks of age was significantly lower for caged than floor

housed hens.

Eggs from caged hens hatched significantly heavier

chicks than the floor housed counterparts which was
attributed to the difference in egg weight observed through

the laying period (Petitte et al., 1982). Measurements on

specific gravity were not reported in this study. Harms et

al. (1984a) found that specific gravity of eggs from hens

with access to litter was higher than hens housed on wire

floors, without a significant difference in egg weight.

They attributed this finding to increased intake of fecal

phosphorous, calcium and other nutrients important to egg

shell formation. Also, they reported that a decrease in

dietary calcium resulted in increased litter consumption.

It appears that caged broiler breeder hens produce larger

eggs with poorer shell quality that result in a concomitant

decrease in hatchability.


Pullet-Layer Transition Period

Bornstein and Lev (1982) discussed their view of the

changing nutritional needs of the bird through the pullet-

layer transition period in terms of flock dynamics. They

concluded, until nearly all the birds in a flock have

started to lay, average flock weights depend more on the

relative proportion within the flock of immature pullets,

prelaying pullets, and laying hens than on the weights of












26
the laying hens. Therefore, any feeding program designed to

promote early egg production also enhances early average

body weights, without necessarily affecting the actual

weights of the laying hens. These researchers found that

earlier maturity and higher egg production were associated

with higher energy intake during the prelay period. The

effect of increased energy during this period on egg weight

was dependent on the age at which the increase in energy was

provided.

McDaniel (1983) showed that quantitative differences in

feed allocation during the prelay period significantly

,affected shell quality and egg weight throughout production.

Increased feed allocation, i.e., 176 g/bird/d, from 17

through 20 wk of age stimulated an earlier onset of

production when compared to a more gradual increase in feed

allocation.

Protein

Research conducted by cave (1984b) showed that protein

levels (15.4 vs. 18.1%) during the prelay period had no

effect on age at 50% production, egg weight, incidence of

cracked eggs, hatchability or mortality. However, the 18.1%

protein treatment showed higher levels of egg production

through 50 wk of age. One possible explanation of this

finding relates to the important changes in the development

of the reproductive system at this time (Yu and Marquardt,

1974). Cave (1984b) suggested that perhaps the higher












27
protein levels improved liver metabolism and function and/or

strengthened the infundibulum which could aid in the

capturing of ovulated yolks. This suggests that as the bird

passes through the pullet-layer transition period a

quantitative change in protein required for the development

of the reproductive tract is separate from the need for body

weight gain (Lilburn, 1987).

Energy

A study conducted by Brake et al. (1985), investigating

protein, energy and their interactions revealed that

significant protein X energy interactions occurred for egg

weight during wk 25 through 44, but not overall. No

differences in the main effect of protein level on egg

specific gravity or fertility were found.

Ingram and Wilson (1987) reported that hens fed ad

libitum for various lengths of time during the pullet-layer

transition period laid at higher rates than their more

restricted counterparts through ca. 43 wk of age*. However,

after wk 44 the hens full fed for 6 to 8 wk laid at a

significantly lower rate than the more restricted birds.

This was perhaps due to excessive levels of body weight gain

past 40 wk which led to body weights in excess of 4.0 Kg by

this time.

Robbins et al. (1988) reported that ad libitu feeding

during the pullet-layer transition resulted in more eggs,

but the effect was not significant. Egg weight and specific













28
gravity were significantly affected by hen age and not feed

treatment.

Lighting Programs

An important management tool that must be considered

along with a planned feeding program is an appropriate

lighting program. A well managed lighting program is a cost

effective way to regulate the onset of sexual maturity. The

objective being the synchronization of sexual maturity,

through feeding and lighting programs, with management

production and scheduling needs. The normal procedure is to

increase the length of the daily photoperiod from an

inhibitory 6 to 12 h/d to a stimulatory photoperiod of 12 to

17 h/d, starting at point-of-lay (Morris, 1967).

Recommendations for light stimulation of breeder

pullets should be strain specific according to Cave (1984a).

He found significant differences in the production response

to abrupt vs. gradual increases in light stimulation for two

different strains of meat-type birds. This finding was

contrary to conclusions drawn by Proudfoot et al. (1980) who

reported no important genotype X photoperiod treatment

interaction when evaluating various abrupt and gradual

lighting programs. However, Proudfoot et al. (1984)

concluded that dwarf genotypes also require a different

light management program than normal strains for optimum

reproductive performance.













Payne (1975) reported that an abrupt increase in
photoperiod from 6 to 16 h/d had a significant effect in

advancing the onset of sexual maturity when compared to a

gradual 1 h/wk increase from 6 to 16 h/d. However, this

procedure produced more smaller eggs than the gradual

increase in photoperiod. He also found that pullets reared

on a 6 h photoperiod then gradually increased to 16 h by 34

wk of age had improved reproductive performance and weighed

significantly less, both at the beginning and end of the

laying period when compared with pullets reared using a

constant 15 h photoperiod.

Whitehead et al. (1987) also compared abrupt vs.

gradual lighting programs. The gradual program started at

18 wk of age and increased .5 h/wk to a maximum 18 h at 38

wk of age. The abrupt program began at 19 wk with a rapid

increase of 1 h/wk to 26 wk then a gradual .5 h/wk increase

to a maximum 17 h at 30 wk of age. The different lighting

programs had no significant effect on any aspect of

reproduction performance in dwarf broiler breeders.

Ingram et al. (1988) demonstrated that initiation of a

stimulatory lighting program at 20 wk was superior to one

initiated at 16 wk of age. Light treatments were ca.

13L:11D increased by 15 or 30 minutes to 15L:9D at 24 wk.

In this experiment, lighting program had a greater effect on

the more restricted (lighter body weight) group.














In two separate experiments conducted by Proudfoot et

al. (1984, 1985) lighting programs were initiated at 16, 20,
or 22 wk of age by abruptly increasing the photoperiod from

8 to 12 h and then further increasing the photoperiod

linearly to 14 h by 23 wk of age. There were no significant

overall effects on egg production, body weights or any other

factor except for the number of double-yolked eggs produced

and the longer delay in sexual maturity. Delaying the

implementation of the lighting program also increased egg

size and decreased specific gravity at 29 wk of age. They

recommended photostimulation at 20 wk of age to avoid

problems of lower shell quality resulting from the delayed

program.

Cave (1984a) utilized two lighting programs beginning

at 20 wk of age. Both increased the photoperiod from 6 to

16 h/d by either 5 abrupt increases of 2 h each week or a

gradual 2 h then 1 h, then 14 increases of .5 h each week.

No overall differences due to lighting program in the number

of hatching eggs per hen housed could be detected. Age at

50% production was delayed significantly and egg weight was

lower for the more abrupt lighting program. These

researchers also reported that light intensity had no

significant overall effect on any production trait, despite

a rather strong change from 2 Ix to 10 Ix at 16, 20, and 22

wk of age. This response was in agreement with findings by

Morris (1967).












31
The effectiveness of a lighting program is complicated

by the feeding program and by seasonal differences in

natural photoperiod and light intensity. Out-of-season

flocks, i.e., those hatched January to May, experience
delayed sexual maturity and poorer reproductive performance.

Brake and Baughman (1989) studied the effect of light source

and intensity during rearing for both in- and out-of-season

flocks. They found that light intensity during the rearing

period may need to be somewhat lower than that of the laying

period in broiler breeders which are exposed to fall

(decreasing natural daylight) conditions during the early

phase of lay. These findings were consistent with data

presented by Morris (1967) suggesting that supplemental

light is most beneficial during fall and winter months of

lay.

Sexual Maturity

It is well known that restricting feed intake of

broiler breeder females during the rearing period will

retard growth and delay the onset of sexual maturity (Lee et

al., 1971; Pym and Dillon, 1974; Watson, 1975; Leeson and

Summers, 1982). When changed from restricted feeding to

either an accelerated or ad libitum feeding program, various

degrees of compensatory growth can occur depending upon the

degree of restriction through the rearing period and the age

at the change. Brody et al. (1980) showed that after severe

feed restriction which delayed the onset of sexual maturity













32
well beyond a normal age, birds did not fully compensate in

growth. Instead body weights remained about 25% lighter

than mature body weights of the control group. When the

severely restricted birds were changed to an ad libitum

feeding program, sexual maturity ensued in a uniform manner.

This study concluded that a minimum body weight and

chronological age were required for the onset of sexual

maturity.

In 1984 five papers on the subject of sexual maturity

appeared, four utilizing broiler breeders and one using

Japanese Quail. Soller et al. (1984b) demonstrated that

body fat content or fat percentage alone is not sufficient

to initiate sexual maturity. More importantly they

concluded that there is a minimum lean body mass requirement

for the onset of sexual maturity in poultry. This finding

was also reported by Zelenka et al, (1984) and OruwarL and

Brody, (1988) with Japanese quail.

Bornstein et al, (1984) confirmed findings of a minimum

requirement for fat and lean tissue stores in conjunction

with chronological age and demonstrated that these

thresholds are strain specific. These researchers, as well

as Pearson and Herron (1982a), reported a significant

negative correlation between age and body weight at first

egg.
Comparisons made by Brody et al. (1984) between normal

and dwarf strains of broiler breeders illustrated the extent














to which differences in body weight and age at sexual

maturity can be affected by genetic variation. Age at first

egg ranged from 153 to 173 d in normal breeders and 167 to

173 d in dwarf breeders. The greatest difference between

pullets at sexual maturity and their nonlaying controls were

in the size of the abdominal fat pad and the reproductive

organs. This result suggests that increases in fat prior to

sexual maturity, instead of being general to the carcass,

are restricted to a few organs related to the partitioning

of energy for reproductive performance.


Breeder Hen Laying Period

Because mature broiler breeders are capable of

consuming feed far in excess of their energy requirement for

maintenance and egg production it is economically

advantageous to formulate broiler breeder hen diets on a

daily nutrient intake basis (Wilson and Harms, 1984).

Pearson and Herron (1981) noted that broiler breeder hens

are sensitive to energy intake during the breeding period.

Extra dietary energy enabled birds to gain more weight (fat)

and this had a depressing effect on egg production,

fertility and hatchability (Pearson and Herron, 1982a;

Spratt and Leeson, 1987a). Furthermore, as the rate of lay

decreases, more energy is available for fat deposition so

the initial negative effects on production are likely to be

maintained or increased through lay.














The degree of sensitivity to energy intake is also
dependent on the season of the year. Chaney and Fuller

(1975) and Luther et al. (1976) reported that egg production

and egg size are reduced more severely by a decrease in

energy intake during the winter than during the summer,

since the energy requirement for maintenance of body

temperature is higher in the winter there are fewer calories

that remain for egg production. These authors suggested

that obesity per se does not reduce egg production since fat

birds can lay at a normal rate, but the obese birds suffer
from excessive mortality which results in depressed levels

of hen-housed production. In addition, McDaniel et al.

(1981a) and Pearson and Herron (1981) demonstrated that

over-consumption of energy by broiler breeder hens adversely

affected hen-day egg production, fertility, hatchability and

specific gravity.

Energy

A successful feeding program based on energy

restriction demands an easily applied and practical

guideline. Bornstein et al. (1979) suggested that the use

of average daily weight gain as an indicator of the degree

of energy restriction would be appropriate. Likewise,

Pearson and Herron (1980, 1981) recommended that body weight

control during egg production be considered as a criterion

for assessing the adequacy of energy intake. The

consequence of this recommendation was clearly illustrated













by Harms (1984) who utilized data from 49 commercial flocks

to construct body weight curves along with their

corresponding production curves for flocks considered to be
making adequate or inadequate body weight gain. Flocks
categorized as making adequate weight gain peaked at a

significantly higher rate of production and maintained a

rate of 80%, or above, 10 times longer (4.6 vs. .4 wk) than

those with inadequate gain.

The energy restriction research conducted by Pearson

and Herron (1980, 1981) showed that the daily energy intakes

of 440 to 452 Kcal ME/bird/d had higher rates of production

when compared to birds fed 363 Kcal ME/bird/d. Egg weights

did decrease by 1 to 4 g depending upon the protein level of

the diet. This work was in close agreement with that of

Waldroup and Hazen (1976) who reported that 425 to 450 Kcal

ME/bird/d would maximize egg production. They also
demonstrated that egg weight and body weight were directly

related to caloric intake. Robbins et al. (1988) concluded

that broiler breeder hens reared on a restricted feeding

program and weighing ca. 3400 g at sexual maturity would

require ca. 500 Kcal ME/bird/d for maximum production. This

level of energy intake approximated ad libitum feeding in

this experiment which may not be the case under different

environmental conditions.

These higher energy values differed from findings by

Spratt and Leeson (1987) who reported that 385 Kcal














ME/bird/d and 19 g of protein were sufficient to maintain

normal reproductive performance of individually caged

broiler breeder females through peak egg production. At 36

wk of age they noted an unexplainable accelerated decline in

egg production along with a drop or no gain in body weight
between 32 and 36 wk of age. This suggests that inadequate

feed allocations were made at this stage and perhaps the

ideal level of energy intake should be higher than the

reported 385 Kcal ME/bird/d.

Research conducted by Leeson and Summers (1982)

demonstrated that excessive energy intake resulted in early

maturity and reduced numbers of settable eggs. Early

maturing birds gained more weight post peak than the control

group even though the feed allowance was identical. This

implies that over-fed birds divert feed energy to body mass

rather than egg production. Peak egg production was 10%

lower than standard and egg size was significantly smaller,

Because obese birds have a higher maintenance requirement

than lighter birds when they mature, initial egg size is

smaller and often not suitable for incubation.

Protein

Waldroup et al. (1976) found that the protein

requirement over the entire production period of broiler

breeders raised on litter and fed a corn-soy diet without

supplemental amino acids was approximately 20 to 22 g/d.

Wilson and Harms (1984) revised their original













recommendations for protein and sulfur amino acid

requirements (Harms and Wilson, 1980) by suggesting that

nutrient specifications for broiler breeders include daily

intakes of 20.6 g protein, 754 mg sulfur amino acids, 400 mg

methionine, 938 mg lysine, 1379 mg arginine, 256 mg

tryptophan, 4.07 g calcium, 683 mg total phosphorous, and

170 mg sodium. Pearson and Herron (1981) recommended 19.5

g/d crude protein when reared on litter and when amino acid

intake was balanced. Caged breeder hens were shown by

Pearson and Herron (1982b) to require 16.5 g/d protein

The absolute energy requirement associated with optimum

production will depend upon the actual maintenance energy

requirement which is likely to differ between cage and floor

systems as well as between strains (Pearson and Herron,

1982b).

Double-Yolked Eggs

The phenomenon of multiple ovulations (double-yolked

eggs) in the chicken has been reviewed by Romanoff and

Romanoff (1949). Zelenka et al. (1986) noted there appears

to be two major categories of multiple ovulations,

sequential and simultaneous. Sequential multiple ovulations

result in extra-calcified compressed-sided eggs, whereas,

simultaneous multiple ovulations result in eggs with more

than one yolk. Conrad and Warren (1940) reported three ways

that double-yolked eggs might occur. First, 65% resulted

from the simultaneous development and ovulation of two ova.













Second, 25% resulted from two ova, which were developing a

day apart, being ovulated simultaneously. Third, the

remaining 10% resulted from successive development and

release of two ova, one remained in the body cavity for a

day and was then picked up by the oviduct along with the

newly released ovum. Zelenka et al. (1986) suggested that

the main cause of double-yolked eggs is that two ova reach

maturity and are released at the same time. They also

reported on the unusual situation where two ova can develop

and be released from a single ovarian follicle. They

suggested that this may have resulted from two separate and

distinct oocytes being encapsulated together by granulosa

layer cells during the initial stages of follicular

development, or incomplete separation of oocytes following

meiotic cytokinesis.

Dobbs and Lowry (1976) utilized dietary dyes to

demonstrate that, in most cases, both yolks were ovulated

within 2 to 3 h of each other. Lowry et al. (1979) reported

that 80% of the pairs developed at the same time and that

ovulation sites were found to occur at random on the surface

of the ovary.

Hormonal mechanisms that control the development of the

ovarian follicular hierarchy were reported by Sharp et al.

(1976) who concluded that multiple ovulation in a super-

ovulatory line of chickens was not due to a defect in the

luteinizing hormone releasing mechanism but to an abnormal













development of ovarian follicles. The inheritance of the

tendency to produce double-yolked eggs through genetic

selection has been demonstrated by Lowry and Abplanalp

(1967), Abplanalp and Lowry (1975), and Abplanalp et al.

(1977). Williams and Sharp (1978) reported that as laying

breeder hens become older, the initial decrease in egg

production and the increase in egg size is a reflection of

the way in which yellow yolk accumulates in a smaller number

of follicles which grow to a larger size before they

ovulate. Furthermore, the incidence of double yolked eggs

is normally reduced to low levels as the breeder hen ages.

Christmas and Harms (1982) summarized data on 12

strains of egg-type hens to determine the influence of

strain and season of the year on the incidence of double-

yolked eggs in the initial stages of lay. They found a

significant strain effect on the incidence of double-yolked

eggs at the onset of lay. The incidence ranged from 1.1 to

3.5% hen-day production. Spring and summer-housed laying

hens produced a greater number of double-yolked eggs than

did those housed in the late fall or winter months. The

incidence of double-yolked eggs and age at 50% production

were significantly correlated, however, it was thought to be

a season rather than a within-strain maturity effect.

Feed restriction during the rearing period has been

shown to limit the production of yellow follicles and the

incidence of double ovulations, leading to an increase in













the number of settable eggs during this period (Fuller et
al., 1969; Chaney and Fuller, 1975; Zelenka et al., 1986;

Hocking et al., 1987, 1989; and Katanbaf et al., 1989b).

Hocking et al. (1989) reported that feed restriction which

resulted in the reduction of the number of yellow follicles

at sexual maturity was associated with lighter, leaner birds

with lower maintenance requirements, but delayed sexual

maturity. Heavier birds were associated with higher numbers

of follicles, whereas, fatter birds were associated with

fewer numbers of follicles. This suggests that a positive

relationship exists between ovulation rate and lean tissue

mass. These authors recommend that feed restriction should

be continued to point of lay.

















CHAPTER III

TOWARDS AN APPROPRIATE STRATEGY FOR WEIGHING
BROILERS, BROILER BREEDER PULLETS AND
BREEDER HENS ON-FARM



Introduction

The ability to estimate average body weight and flock

uniformity accurately is an important part of breeder and

broiler managers' duties. Average body weight estimates of

commercial flocks are used constantly to evaluate breeder

growth and development relative to a particular strain's

standard. Decisions concerning the proper feed allocation

required to consistently achieve a target body weight

objective over a period of time are based on these estimates

and any error in their accuracy will be reflected in the

inefficient growth and production of the flock. Also,

decreases in flock uniformity, i.e., increased variation in

body weight, is a sign of suboptimum husbandry conditions,

the cause of which must be identified and corrected in a

timely manner or production inefficiencies will persist or

worsen.

An appropriate weighing program is an important process

that assures the maintenance of technical and economic

efficiencies in the pullet and breeder houses as well as the

















CHAPTER III

TOWARDS AN APPROPRIATE STRATEGY FOR WEIGHING
BROILERS, BROILER BREEDER PULLETS AND
BREEDER HENS ON-FARM



Introduction

The ability to estimate average body weight and flock

uniformity accurately is an important part of breeder and

broiler managers' duties. Average body weight estimates of

commercial flocks are used constantly to evaluate breeder

growth and development relative to a particular strain's

standard. Decisions concerning the proper feed allocation

required to consistently achieve a target body weight

objective over a period of time are based on these estimates

and any error in their accuracy will be reflected in the

inefficient growth and production of the flock. Also,

decreases in flock uniformity, i.e., increased variation in

body weight, is a sign of suboptimum husbandry conditions,

the cause of which must be identified and corrected in a

timely manner or production inefficiencies will persist or

worsen.

An appropriate weighing program is an important process

that assures the maintenance of technical and economic

efficiencies in the pullet and breeder houses as well as the













processing plant. A weighing program is considered

appropriate for a particular attribute (mean body weight and

flock uniformity) in a particular field condition

(restricted or full fed) if it satisfies several conditions.

First, the accuracy of the estimated attribute must be as

good as, or better than, a level required to achieve an

objective. The objective in this case is to determine the

best nutrient allocation or other management decision

necessary to achieve body weight and uniformity standards.

Secondly, the cost of conducting a weighing program must be

within the practical limits of resources available.

A review of the various management guides published by

the breeder companies confirms the lack of consensus

concerning suggested weighing procedures. Recommendations

range from weighing 1, 2, or 3% of the flock to sampling 2,

3, or 4 locations in a house. Furthermore, none of the

management guides quantify for the breeder manager what

level of technical or economic inefficiency will result if

the procedures are not followed.

There has been little or no research conducted on

weighing procedures that maintain a practical level of

accuracy of the weigh data while minimizing the cost of

collecting those data.

The objective of this study was to establish general

guidelines for the development and implementation of an

appropriate weighing program. Specifically, the objectives













of Experiment 1 were to quantify the cyclic nature of body

weight gain in a 48 h period and to demonstrate the degree

of error in estimating gain when weighing programs are not

scheduled at a consistent time interval. The objectives of

Experiment 2 (on-station) and 3 (on-farm) were to determine

the effect of scale type, sample units (individual vs.

group), sample size, sample location, time of sampling, and

complexity of procedures used in the on-farm weighing of

broilers, broiler breeder pullets and breeder hens on

average body weight gain and uniformity.



Materials and Methods

Experiment 1

Trials 1 and 2. Eight pens containing 16 Arbor Acres

broiler breeder females, 25 wk old and not yet in

production, were divided into two feeding programs. The

first, an early feeding time (ERL) allocated 122 g of

feed/bird/d at 0430 h and the second, a late feeding time

(LTE) allocated an equivalent amount of feed at 1530 h.

Each feeding program consisted of two groups of two pens

each with a significant difference in average body weight

between groups. These weight class groupings (trials) could

then simulate different houses or farms and the effect of

initial body weight evaluated. Each pen was weighed, eight

birds per crate (two crates per pen), at 2 h intervals

starting at 0430 h and ending at 2030 h on the first day,












44
with the same procedure repeated the following day. Crated

birds were weighed on an electronic scale (Detecto, model

EF-218-56) with a gross capacity of 90.7 kg (200 lb) and a

precision of 45 g (0.1 Ib). The four crate weights for each

trial were pooled and the average body weight and change

(gain or loss) for each time period calculated.

Experiment 2

Trials 1. 2 and 3. Three weight class groupings,

totaling 274 Arbor Acres broiler breeder females, 41 wk old

and near peak production, were used to test the accuracy of

different types of scales (electronic vs. mechanical) and

sample units (individual vs. group) in determining average

body weight and uniformity. Three groupings (trials) were

used to simulate body weight conditions found on different

farms. Each trial consisted of six pens containing ca. 15

adult breeder hens. Birds were crated seven or eight birds

to a crate depending upon the population size within a pen.

The weigh routine was as follows: crate weights (GRP)

were measured on an electronic Detecto scale to the nearest

45 g; birds were individually (IND) removed from the crate

and weighed, first on an electronic (ELC) scale (Weltech,

model BW-1) to the nearest 1.0 g and then on a mechanical

(SPR) spring scale (Salter, model 235) to the nearest 45 g.

All weighing were conducted by the same person and data

recorded by a technician to expedite the flow of procedures.













Experiment 3 (on-farm)

General procedures. A catching pen was used to pen-up

a sample of birds as large as possible without causing

excessive piling. Samples were measured at two locations in

each on-farm house with each house considered a trial. The

first location was along the side wall near a feed dump

(FDD). The second, an end location (END) was along the side

wall at the end door. Birds were weighed individually on a

mechanical SPR scale. Birds in the first pullet house only

were weighed individually on the ELC scale to validate

earlier findings concerning type of scale used.

Weighing procedures were as follows. The weigher

selected and weighed individual birds from the penned-up

sample. A subjective decision was then made to note all

grossly under- or overweight birds as suspected outliers.

This process continued until a predetermined fixed quantity

of bird weights (N=60) was achieved and the last weight

noted. Weighing was then continued until all remaining

penned birds were weighed. All recorded weights were

tabulated under the following treatments: fixed quantity

with suspected outliers included (FXD); fixed quantity with

outliers removed (FXO); and all birds penned including

suspected outliers (PND). Two weeks after the initial

weighing these procedures were repeated in the morning (AM)

for Trial 1 and 2, and afternoon (PM) for Trial 1 only.

Follow-up time of AM weighing was within one hour of the











46
initial weigh time and PM weighing were approximately five

hours after AM weighing.

Pullet farm. Two dark-out houses (Trials 1 and 2)

containing ca. 14,500 replacement pullets were sampled when

8 and 10 wk old on the off-feed day during a skip-a-day

feeding program. Birds were fed at 0700 h and water was

restricted in the afternoon. Each house was equipped with

pan type feeders and nipple drinkers.

Breeder farm. Samples of birds were weighed in two

curtain-sided breeder houses (Trials 1 and 2) containing ca.

7,350 adult breeder hens 36 and 38 wk old and in their tenth

and twelfth week of production. Hen-day production was

about 74% at that time. Females ate from chain feeders and

drank from bell-type waterers, while males ate separately

from pan feeders.

Broiler farm. Body weight measurements were made in

three curtain-sided broiler houses (Trials 1, 2, and 3).

The first was recently built and equipped with nipple

drinkers, pan feeders and contained ca. 24,500 straight-run

broilers 40 d old. The other two were older houses and were

equipped with cup drinkers, pan feeders and each contained

ca. 14,500 straight-run broilers 38 d old.

Statistical Analysis

The TTEST procedure of SAS/STAT (1985) was used to

calculate means for a particular variable under

investigation, and then to test the hypothesis that the












47
means of two groups of observations were equal. The F-test

ratio of sample variance (Montgomery, 1984) was used to test

the hypothesis that the variance of two groups of

observations were equal. Differences between groups of

observations were considered significant if P < .05.



Results and Discussion

Experiment 1

Time of weighing. Initial body weights prior to

feeding on the first day were 2582 and 2676 g for Trial 1

and, 2747 and 2727 g for Trial 2 (Table 3-1). Change in

body weight (gain or loss) data from the pooled trials

(Table 3-1) demonstrate (Figure 3-1) how birds on the LTE

program reached a 205 g peak change in body weight in 3 h

after feeding, which was greater than the 155 g peak change

in the ERL program which also occurred at 4 h after feeding.

Birds on the LTE program lost weight, starting from peak

body weight and ending just prior to feeding, at the rate of

8.6 g/h while the rate for the ERL program was slower at 7.1

g/h. These differences in feeding programs suggest that

birds on a LTE program may require greater quantities of

water. The higher level of gain due to possible increased

water intake could explain the greater mass lost over this

time period. This finding also suggests that water

restriction should not begin for at least 4 h after birds

have finished eating.













Figure 3-2 clearly illustrates the cyclic changes in

body weight over a 40 h period when fed on an ERL schedule.

Any change from the initial time of weighing to the follow-

up weighing will create an error in the estimated gain. For

example, an initial weighing at 0830 h followed by a

weighing the second day at 0830 h resulted in a 22 g

increase while a weighing at 1030 h will have a potential

error of 7 g by showing a gain of 15 g. If the birds are

weighed on the follow-up day in the afternoon at 1430 h the

estimated change in body weight is a loss of 27 g, or a

difference of 49 g from 0830 to 1430 h. The true gain for

the first 24 h period was 14 g, which was measured from just

prior to feeding (0430 h) on day one, to just prior to

feeding on the second day. This would suggest that weighing

just prior to feeding would be the most effective procedure

in evaluating gain which is in agreement with findings by

Turner et al., (1983). The drawback to this procedure with

feed restricted birds is the almost frenetic behavior of the

birds at this time that could cause accidental mortality.

Breeder company suggestions to weigh at noon or ca. 3 to 4 h

post-feeding would find the birds at their greatest level of

feed and water intake. Body weights could be rising or

declining at this time, along with the possibility of

significant variation in body weights caused by vomiting.

Furthermore, afternoon hours for weighing should be

discouraged in the summer to avoid stressing the birds













during the hours of highest temperatures. An ERL feeding

schedule coupled with an evening weigh program is one

logical alternative; birds have settled down, voided most

feed, water and eggs, and temperatures are cooler. In this

scenario, variation in body weights as well as undue stress

could be minimized at no additional cost to the program.


Experiment 2

Scale type. Average body weight estimates measured on

the SPR scale were numerically higher but not significantly

different from measurements made on the ELC scale (Table 3-

2). The on-farm validation of these findings was upheld in

Experiment 3. An observation noted during these experiments

was that the automatic printing feature of the ELC scale

decreases the possibility of a transcription error and the

time (cost) necessary for weighing.

Sample unit. All trials conducted on-station

demonstrated that the average body weight determined by

individually weighing birds was not significantly different

than group weighing with crates of seven or eight birds

(Table 3-2). However, the estimates of flock uniformity as

measured by the standard deviation (SD) among observations

was significantly greater and more representative of the

true flock uniformity, when birds were weighed individually.













Experiment 3 (on-farm)

Location Effect

Straight-run broilers. Body weight and body weight

uniformity estimates for the FDD and END house locations are

presented in Table 3-3. In general, broiler weights and

flock uniformity were not found to be different between

locations. There was a significant difference in average

body weight in Trial 3, which was attributed to the chance

occurrence of a slightly higher ratio of males sampled at

the FDD location at that particular sampling.

Pullets. Average body weight was not found to be

different between locations in either trial or at the ages

tested (Table 3-4). This observation would tend to be

consistent with findings of Van Krey and Weaver (1988) in

which it was shown that all semblance of social order

disappears during the period of frenetic feeding.

Significant differences in uniformity were found at the two

locations in trial one at 8 and 10 wk of age. The greater

variation at the FDD location was attributed to including

suspect outliers in the sample. Removal of these

observations on the basis of their being true outliers, as

shown in Table 3-7, resulted in levels of uniformity at both

locations that were no longer significantly different.

Breeders hens. A statistical difference in average

body weight of breeder hens due to house location was found

in Trial 1 at 36 and 38 wk of age without there being a













difference in uniformity (Table 3-5). However, the END

location was greater at 36 wk while the FDD was greater at

38 wk. Furthermore, the 38 wk, PM weighing failed to detect

differences in location suggesting that the END location

actually gained weight during the day by feeding and

drinking later. Perry et al. (1971) noted that after

laying, a period of feeding and drinking followed, which

suggests earlier laying by the END location. Trial 2 does

not substantiate these findings. No significant differences

in average body weight or uniformity between locations were

detected for any PND sample. It is difficult to determine

from these data if the differences found in Trial 1 at the

various ages were due to changing flock dynamics or sampling

error. Consistency in the uniformity data as well as the

low number of detected outliers suggests that there could be

significant behavioral differences at various locations in

the house. Appleby et al. (1984) found considerable

movement of both males and females throughout the house.

However, their study was conducted in buildings 46 m long,

whereas these data were collected in buildings 122 m in

length.

Time of weighing. The importance of consistently

weighing at the same time each scheduled weighing

(Experiment 1) is underscored with breeder pullets and

laying breeder hens. Two principal observations can be made

from the data presented on both AM and PM weighing in













Tables 3-4 and 3-5, which are evaluated and presented in

Table 3-6. First, the measurement of average body weight

gain of the pullets decreased by ca. 10 g/h between the AM

and PM weighing, despite the fact they were off feed. This

was determined from Table 3-6 where the difference in pullet

body weight from AM to PM at 10 wk (Trial 1) ranged from a

loss of 43 g to 67 g over the 4 h period. Secondly, average

body weight gain data for the adult breeder hens were not as

conclusive. Birds in the FDD location gained weight over

the two week period in both Trial 1 (66 and 77 g) and Trial

2 (141 and 142 g), however they lost weight (-8 and -35 g)

between the AM and PM weighing in Trial 1. This was in

marked contrast to birds weighed at the END location which

lost considerable weight (-141 and -159 g) over the two week

period but gained back nearly 25-30% of it (36 and 60 g)

between the AM and PM trials. The principal conclusion

being that flock dynamics in the breeder house contribute to

a complex situation where relatively radical changes in body

weight occur throughout the day. This is especially true

during the morning hours when feeding, drinking and laying

are all contributing to variation in body weights.

Outliers. Information required to determine if a

grossly under- or overweight bird should be rejected as a

true outlier to the normal body weight distribution is

presented in Table 3-7. No true outliers were detected in

the straight run broiler flocks. Half of the suspected













outliers in the breeder flocks were true outliers and their

inclusion in flock uniformity estimates could confound

interpretations. In the pullet flocks five out of 41

suspected outliers were classified as true outliers. Three

of the five were missexed males and two were either sick or

starve-outs.

Sample size. The average body weight and uniformity

measurements for FXD quantities of breeders and pullets were

not significantly different than PND quantities (Table 3-4).

Figure 3-3 illustrates the effect of a weigh procedure that

prescribes weighing a fixed quantity of birds, i.e., 60

pullets while rejecting suspected outliers (A) on the

frequency distribution of confidence intervals. Compared to

this procedure is a distribution of confidence intervals

that resulted from weighing all pullets in a penned-up

sample (B). The greatest number of suspected outliers in a

pullet flock were, by far, under-weight birds. Therefore,

rejection of these observations would tend to inflate the

mean body weight. Rejection of the extremes of a

distribution, i.e., grossly under- and over-weight birds may

lower the level of sample variance which may therefore

deviate from the true population variance. By weighing all

birds in the penned-up group it should be possible to have

more confidence that the mean estimates the true population

mean.













Sample size relative to flock size was determined by

sequentially adding 10 pullets or 20 breeders to their

respective samples, while evaluating the change in variance

as measured by the standard deviations, Table 3-8. A

stabilized level of sample variance would indicate that the

sample size achieved a level where additional observations

would not change the estimate of the population variance.

The sample variance peaked with a sample size slightly under

one percent of the population for the straight-run broilers

and pullets tested in these trials. Estimated sample

variance in a breeder flock peaked at only 0.5% of the

population. These levels of peaked variance would define an

absolute minimum sample size that could be used to estimate

flock body weight and uniformity.

It is known that the statistical accuracy of a sample

estimate generally increases with the sample size as a

percent of the flock size, number of sampling locations

selected per house, and the complexity of the sampling

procedures used. However, an increase in the sample size,

and/or number of locations will increase the cost of

weighing and disrupts the flock. Therefore, the choice of

an appropriate method of weighing broilers, broiler breeder

pullets, and breeder hens is primarily concerned with

maintaining the proper balance between the sample size and

number of locations that achieve a minimum cost without













sacrificing an adequate level of accuracy for the decision

making process.

In summary, this study demonstrated that the required

balance between accuracy and efficiency of an appropriate

weighing program could be maintained if average body weight

and flock uniformity estimates were derived from one

convenient location, weighing all birds in a penned-up

sample, a number of penned-up samples with a total bird

count approximating at least one percent of the flock size,

and weighing conducted at the same time each weigh period.

Those elements of a comprehensive weighing program that

have the greatest impact on the level of accuracy of the

estimate, but do not add appreciably to the total cost of

data collection, e.g., time of weighing, should certainly be

given the greatest consideration.














TABLE 3-1. Effect of feeding time (ERL vs. LTE) and time of day on non-laying broiler
breeder female mean body weight and weight change (Exp. 1)

ERLa LTEa
Trial lb Trial 2 Pooled Trial 1 Trial 2 POOLED
Time BWT Change BWT Change BWT Change BWT Change BWT Change BWT Change
Day (h) (g) (g) (g) (g) (g) (g) (g) (g) (g) (g) (g) (g)

1 04:00 2582c NA 2747c NA 2664 NA 2785 NA 2818 NA 2801 NA
04:30 FEED FEED FEED
06:30 2723 140 2864 118 2794 129 2774 NA 2806 NA 2790 NA
08:30 2755 173 2884 138 2820 155 2754 NA 2792 NA 2773 NA
10:30 2737 155 2883 136 2810 145 2724 NA 2774 NA 2749 NA
12:30 2725 143 2872 125 2798 134 2708 NA 2754 NA 2731 NA
14:30 2701 119 2842 95 2772 107 2676c NA 2727c NA 2701 NA
15:30 FEED FEED FEED
16:30 2670 88 2816 70 274 79 2839 182 2889 176 2864 179
18:30 2670 88 2806 60 2738 74 2870 213 2910 197 2890 205
20:30 2647 65 2795 48 2721 57 2859 202 2896 183 2877 192

2 04:00 2601 19 2755 9 2678 14 2794 118 2822 95 2808 106
04:30 FEED FEED FEED
06:30 2747 165 2896 150 2821 157 2785 110 2815 88 2800 99
08:30 2769 188 2916 170 2842 179 2767 91 2813 86 2790 89
10:30 2772 191 2899 153 2835 172 2745 70 2802 75 2774 72
12:30 2750 168 2881 135 2816 152 2720 44 2779 52 2750 48
14:30 2727 145 2859 113 2793 129 2694 19 2757 30 2725 24
15:30 FEED FEED FEED
16:30 2700 118 2835 89 2767 104 2779 104 2832 105 2806 104
18:30 2679 97 2818 72 2748 84 2874 199 2910 183 2892 191
20:30 2663 81 2806 60 2735 71 2879 203 2900 173 2889 188

aERL= Early feed time (0430h); LTE= Late feed time (1530 h); NA=Not applicable.
bTrial 1 and 2, average of two pens.
"Initial body weight prior to feeding.














TABLE 3-2. Effect of scale type (ELC vs. SPR) and sample
unit (IND vs.GRP), on mean adult breeder hen and breeder
pullet body weight and uniformity (SD), (Exp. 2)

Age Trial Scale type Sample unit

(wk) No. ELC SPR Sig. IND GRP Sig.

38 1 N no. 90 90 90 12
mean, g 4029 4063 NS1 4029 4074 NS
SD, g 399 399 NS2 399 196 *

38 2 N no. 90 90 90 12
mean, g 3781 3811 NS 3881 3874 NS
SD, g 336 331 NS 336 152 *

38 3 N no. 94 94 94 12
mean, g 3597 3624 NS 3597 3644 NS
SD, g 319 322 NS 319 125 *

40 1 N no. 90 90 90 12
mean, g 4036 4063 NS 4036 4053 NS
SD, g 415 419 NS 415 191 *

40 2 N no. 89 89 90 12
mean, g 3816 3842 NS 3816 3797 NS
SD, g 361 360 NS 361 237 *

40 3 N no. 94 94 94 12
mean, g 3635 3663 NS 3635 3632 NS
SD, g 320 325 NS 320 289 *

8 4 N no. 111 111
mean, g 844 855 NS -- --
SD, g 130 133 NS --- --

8 5 N no. 107 107
mean, g 862 847 NS -- --
SD, g 101 97 NS -- --


1 t-test on sample means (
2 F-test ratio on sample v
ELC= Electronic scale
SPR= Spring scale
IND= Individually weighed
GRP= Group weighed


P<.05).
ariance (P<.05).
SD= Standard deviation
Sig= Significance (P<.05)














TABLE 3-3. Effect of sample location (FDD vs. END) and
sample type (PND vs. FXD) on mean straight-run broiler body
weight and uniformity (SD),(Exp. 3)

Age Trial Pop. Sample Location
(d) No. Size Type FDD END Sig. Pooled

40 1 24,500 PND N, no. 70 78
mean, g 1683 1663 NS1
SD, g 198 199 NS2

PND N no. 81 87
mean, g 1674 1708 NS
SD, g 206 232 NS


All N no. 151 165 316
mean, g 1678 1687 NS 1683
SD, g 202 217 NS 210

FXD N no. 50 --
mean, g 1670 ---
SD, g 211 ---

38 2 14,500 PND N no. 100 65 165
mean, g 1562 1551 NS 1558
SD, g 199 173 NS 189

FXD N no. 50 ---
mean, g 1623 ---
SD, g 228 ---

38 3 14,500 PND N no. 80 86 166
mean, g 1665 1564 1613
SD, g 194 196 NS 201

FXD N no. 50 --
mean, g 1566 ---
SD, g 212 ---


It-test on sample means (P<.05).
ZF-test ratio on sample variance
FDD= Feed dump location
END= End location
PND= All birds penned
FXD= Fixed quantity


(P 0.05).
SD= Standard deviation
Sig= Significance (P<.05)













TABLE 3-4. Effect of sample location (FDD vs. END) at
various ages and by sample type (PND vs. FXD) on mean pullet
body weight and uniformity (SD), (Exp. 3)

Trial 1 Trial 2
Age Location Location
(wk) Time Type FDD END Sig. FDD END Sig.

8 AM PND N no. 111 107 113 100
mean, g 855 847 NS 854 873 NS
SD, g 133 97 129 131 NS

FXD N no. 60 60 60 60
mean, g 890 862 NS 866 884 NS
SD, g 142 97 131 133 NS

10 AM PND N no. 92 72
mean, g 991 1033 NS 1022 1033 NS
SD, g 146 140 NS 156 159 NS

FXD N no. 60 60 60 60
mean, g 1031 1050 NS 1032 1027 NS
SD, g 138 134 NS 167 163 NS

10 PM PND N no. 88 96 --- --
mean, g 948 974 NS --- --
SD, g 168 145 -- --

FXD N no. 60 60 --- --
mean, g 974 984 NS --- --
SD, g 162 143 NS --- ---

St-test on sample means (P<.05)
2 F-test ratio on sample variance (P].05).
FDD= Feed dump location SD= Standard deviation
END= End location Sig= Significance (P..05)
PND= All birds penned
FXD= Fixed quantity















TABLE 3-5. Effect of sample location (FDD vs. END) at
various ages and by sample type (PND vs. FXD) on mean
breeder hen body weight and uniformity (SD), (Exp. 3).

Sample TRIAL I. TRIAL 2
Age/Time type FDD END Sig. FDD END Sig.

36 wk/AM PND N no. 69 69 77 70
mean, g 3291 3387 3342 3388 NS
SD, g 241 268 NS- 310 226 N'S

FXD N no. 60 60 60 60
mean, g 3296 3385 3337 3412 NS
SD, g 252- 261 NS 295 330 NS

38 wk\AM PND N no. 64 64 64 64
mean, g 3356 3245 3482 3403 NS
SD, g 356 300 NS 326 292 NS

FXD N no. 60 60 60 60
mean, g 3373 3240 NR 3478 3395 *
SD, g 356 300 NS 362 298 NS

38 wk\PM PND N no. 62 62
mean, g 3348 32S1 NS -.- --
SD, g 320 268 NS -

FXD H no. 60 60
mean, g 3338 3286 NS --- ---
SD, g 321 271 Ng --


"t-test on sample means
"F-test ratio on sample
FDD= Feed dump location
EID= End location
PND= All birds penned
FXD= Fixed quantity


(P<.05).
variance (P$.05).
SD= Standard deviation
Sig= Significance (PS.05)














TABLE 3-6. Effect of sample
breeder hen and pullet body


Sample Age interval
type (Age, wk; Time)


location (FDD vs.
weight gain (Exp.


Trial 1
FDD END
(g) (g)


END) on mean
3)


3)


Trial 2
FDD END
(9) (g)


Breeder hen

PND (36;

FXD (36;


AM)

AM)


to (38;

to (38;


AM)

AM)


-141

-159


(36; AM) to (38; PM) 58 -105 --

(36; AM) to (38; PM) 42 -99 --

(38; AM) to (38; PM) -8 36 --

(38; AM) to (38; PM) -35 60 --


t


(8;

( 8;


AM)

AM)


to (10;

to (10;


AM)

AM)


135

141


186

188


( 8; AM) to (10; PM) 92 127 --- ---

( 8; AM) to (10; PM) 84 122 --- ---

(10: AM) to (10; PM) -A4 -59>q --


(10;


AM)
AM)


(10;


PM)-
PM)


-56


-67


1 Age interval= 36 wk of
or PM weighing.
FDD= Feed dump location
END= End location
PND= All birds penned
FXD= Fixed quantity


age AM weighing to 38 wk of age AM

SD= Standard deviation
Sig= Significance (P<.05)


141

142


16

-16


PND

FXD

PND

FXD

Pulle
PND

FXD


PND

FXD

PND

FXD


167

167


160

143













TABLE 3-7. Classification of suspect outliers as true
outliers by testing mean body weight with an outlier
interval ( 3*SD) for broilers, pullets and breeder hens
(Exper. 3)

Outlier
Trial Mean 3*SD Interval Suspect Actual
(no.) Age N (g) (g) (g g) (no.) (no.)

Broilers

1 40 d 316 1683 629 (1054, 2312) 4 0

2 38 d 165 1556 566 ( 990, 2122) 1 0

3 38 d 166 1615 603 (1012, 2218) 1 0


Breeder hens

1 36 wk 138 3339 776 (2563, 4115) 0 0

2 36 wk 147 3373 896 (2477, 4268) 2 2

1 38 wk 128 3300 998 (2303, 4298) 2 1

2 38 wk 128 3443 980 (2462, 4423) 4 1

Pullets

1 8 wk 218 851 350 ( 501, 1202) 7 2

2 8 wk 213 863 390 ( 473, 1252) 9 0

1 10 wk 164 1009 434 ( 575, 1444) 12 0

2 10 wk 162 1026 471 ( 555, 1497) 13 3














TABLE 3-8. Effect of sample size on mean and variance of
body weight for broilers, pullets and breeder hens.

N Mean SD N Mean SD

Breeder hens

10 3560 233 10 3451 194
20 3465 301 20 3363 244
30 3433 382 30 3391 249
40 3394 360 40 3386 291
50 3411 343 50 3373 275
60 3414 333 60 3385 261
70 3387 326 70 3390 268
80 3384 316 80 3378 257
90 3387 305 90 3368 256
100 3387 297 100 3339 265
110 3357 318 110 3344 261
120 3353 309 120 3347 261
130 3364 312 130 3344 270
140 3364 320 140 3338 259

Broilers Pullets

20 1707 161 20 870 123
40 1718 187 40 889 126
60 1702 198 60 885 113
80 1693 195 80 866 112
100 1687 201 100 862 111
120 1690 198 120 855 132
140 1693 201 140 859 128
160 1685 199 160 857 124
180 1680 200 180 860 119
200 1683 202 200 861 116
220 1683 212 220 853 117
240 1689 212
260 1690 211
280 1692 206
300 1676 206

















2.85

2.83

2.81

2.79

2.77
2,77
2.75

2.73


0:30 DO:30 14:30 I:30O Z:30 OZ:30 06:30 10:30 i4:30 10:30
TIME PERIODS


FIGURE 3-1. Effect of early feeding schedule and time of
weighing on broiler breeder female body weight (Exp. 1).


201 A A A A
05:30 10:30 14:30 18:30 22:30 02:30 06:30 10:30 14:30 18:30

M EARLY EED SCHEDULE T TIME PER I ODS + LATE FEED SCHEDULE
[3 ..L', FEEo sCHEOULC


FIGURE 3-2. cyclic changes in non-laying breeder female body
weight, on an early or late feeding schedule.














1.06-


1.04-


1.02-


1.00 -


0.98


0.96


0.94


0.92


1


....
---

......


50%


70%


90%


CONFIDENCE INTERVAL, %


FIGURE 3-3. Frequency distribution of confidence intervals for
a fixed quantity of birds excluding outliers (A) and all birds
penned-up in a flock (B)


I

















CHAPTER IV
THE EFFECT OF SEVERE FEED RESTRICTION
DURING THE REARING PERIOD ON FEMALE
BROILER BREEDER REPRODUCTIVE PERFORMANCE




Introduction
Early studies that examined the effect of feed

restriction on reproductive performance utilized ad libitum

feeding as the bench mark or control group in their

experimental designs. A generalized model illustrating this

effect was proposed by Bullock et al. (1963), where they

postulated that the only response to restricted feeding is a

delay in sexual maturity, characterized by the displacement

or shifting of the production curve to older ages. Since

then, numerous research projects have shown that relative to

ad libitum controls, feeding programs that restrict the feed

intake of broiler breeder females during rearing will delay

sexual maturity (Lee et al., 1971; Harms et al., 1979;

Leeson and Summers, 1982), increase initial egg size (Blair

et al., 1976; Leeson and Summers, 1982), decrease the number

of doubled-yolked eggs and therefore increase the number of

settable eggs (Fuller et al., 1969; Chaney and Fuller, 1975;

Christmas and Harms, 1982; Hocking et al., 1989; Katanbaf et

















CHAPTER IV
THE EFFECT OF SEVERE FEED RESTRICTION
DURING THE REARING PERIOD ON FEMALE
BROILER BREEDER REPRODUCTIVE PERFORMANCE




Introduction
Early studies that examined the effect of feed

restriction on reproductive performance utilized ad libitum

feeding as the bench mark or control group in their

experimental designs. A generalized model illustrating this

effect was proposed by Bullock et al. (1963), where they

postulated that the only response to restricted feeding is a

delay in sexual maturity, characterized by the displacement

or shifting of the production curve to older ages. Since

then, numerous research projects have shown that relative to

ad libitum controls, feeding programs that restrict the feed

intake of broiler breeder females during rearing will delay

sexual maturity (Lee et al., 1971; Harms et al., 1979;

Leeson and Summers, 1982), increase initial egg size (Blair

et al., 1976; Leeson and Summers, 1982), decrease the number

of doubled-yolked eggs and therefore increase the number of

settable eggs (Fuller et al., 1969; Chaney and Fuller, 1975;

Christmas and Harms, 1982; Hocking et al., 1989; Katanbaf et













al., 1989b), increase livability (Lee et al., 1971; Wilson

and Harms, 1986, Katanbaf et al., 1989a), increase fertility

and hatchability (McDaniel et al., 1981b; Bilgili and

Renden, 1985), and improves egg production (Leeson and

Summers, 1982; McDaniel, 1983; Wilson and Harms, 1986;

Hocking et al., 1987; Katanbaf et al., 1989b). These

effects will also be influenced by photoperiod, temperature

and other environmental factors that can alter the

reproduction process.

The primary breeder companies currently recommend

various degrees of feed restriction for their particular

strain which permit a relatively narrow range of growth

curves to be followed in different environments. The

optimality of these prescribed standards are of issue and

raise interest in feed allocations below current

recommendations (severe restriction).

If the overall objective of the breeder manager is to

maximize the number of placeable chicks per hen housed over

a normal production period, then the optimal growth curve

and corresponding feeding program for a particular strain

must be identified. The growing consensus is that current

recommendations lead to an overweight breeder flock that

does not meet this objective.

Therefore, the overall objective of this experiment was

to evaluate the breeder's recommended growth curve by

determining the relationship between various degrees of













severe feed restriction (relative to breeder

recommendations) and subsequent effects on the more specific

evaluation criteria: body weight, sexual maturity, mortality

and other hatching egg production parameters that impact on

the production of placeable chicks per hen housed.



Materials and Methods
Stock and Management

Male and female Arbor Acres strain broiler breeders,

hatched in-season at a commercial hatchery (September, 1987)

and vaccinated for Marek's disease before placement were

used in this experiment. A total of 860 day-old female

chicks were randomly placed into 20 litter-floor pens of an

open-sided house. Each 3.1 X 3.6 m pen was equipped with an

automatic waterer for ad libitum drinking and three pan type

feeders. Male chicks were group reared separately in a

litter-floor pen of an open sided-house and fed according to

breeder recommendations. At 20 wk of age all males were

individually weighed and 60 males, weighing between 2650 and

2950 g, were randomly placed 3 per female pen. Sixty

replacement males (12 per treatment) were randomly placed in

pens in a separate house and maintained on respective feed

treatments. All birds were beak trimmed and vaccinated for

fowl pox at 10 d of age. Birds were vaccinated for

Newcastle disease and infectious bronchitis at 2, 5, 12, and

15 wk of age, and avian encephalomyletitis and fowl pox at













10 wk of age. Chicks were reared under natural daylight

conditions until 20 wk of age, then daylength was abruptly

increased from ca. 12 h to 15 h by supplementing with

incandescent light, ca. 22 lux at bird level, from 0430 h to

1930 h, E.S.T.

Feed Treatments

Birds were fed ad libitum until 2 wk of age and

restricted daily during the third week on a starter diet

(Table 4-1). All birds were fed on a skip-a-day basis a 16%

grower diet from 4 through 8 wk, a 12% grower diet from 9

through 15 wk, and a 16% grower diet from 16 through 19 wk

of age. Five feed treatment groups based on a standard

feeding program were used. The feed treatments were

designed to have body weight follow growth curves over the

life cycle that were: 8 percent above the breeder

recommended standard curve (+8%); standard (STD), which

approximated the breeder's standard curve; and 8 (-8%), 16

(-16%) and 24 (-24%) percent below the standard curve. Feed

allocations for the STD treatment were derived from average

weekly body weight estimates and all other feed treatments

adjusted quantitatively. Daily feeding of a laying diet

began at 20 wk of age, where the nutrient intake, other than

energy provided per bird per day, was based on current

recommendations (Wilson and Harms, 1984). This intake

furnished for the STD treatment 20.6 g protein, 754 mg

sulfur amino acids, 4.07 g Ca, 683 mg total P, and 170 mg














Na, per bird per day (Table 4-2). Adjustments in diet
formulation and allocation were made weekly based on level

of body weight gain and egg production.

Production Measurements

Egg production and mortality records were kept daily.
Egg production was summarized by phase of maturity, that is,
pullet (1 d to 5% production) or breeder hen (5% production
to 65 wk of age). Average body weight was determined weekly

for each pen by weighing four groups of ca. 8 females and

one group of 3 males through 45 weeks and then bi-weekly
until 62 weeks of age. Average body weight of the STD

treatment was compared With a target body weight recommended

by Arbor Acres for a particular age, and a feed allocation
made. Feed allocations for all other feed treatments were
quantitatively adjusted from this allocation to STD.

Eggs were collected three times daily, classified as
double-yolked or normal and stored in an egg cooler at 13 C.

Production was recorded daily and summarized by 14 d
periods. Average egg weight was determined weekly by

individually weighing all normal eggs from one day's

production. Specific gravity was determined once per 4 wk

period, from 30 through 62 wk of age, by weighing eggs

individually then, storing one day's egg production

overnight and the next morning using the saline flotation

method with solutions set at intervals of 0.0025 g/mLm

Fertility and hatchability were determined every 4 wk from













32 to 64 wk using four days production, ca. 100 settable

eggs, from each pen and set according to normal incubation

procedures.

Research Period and Environment

The relationship of average weekly temperature (highs

and lows), and hours of daylight to the research period is

illustrated in Figure 4-1. Birds were hatched in September,

1987 and commenced production in early March, 1988. The

onset of production coincided with increasing temperatures

and hours of natural daylight.

Experimental Design and Statistical Analysis

The experimental design was a randomized complete block

of five pens replicated 4 times and containing 36 female and

3 male broiler breeders from 28 wk until termination (less

female mortality). The experimental unit was the pen.

Forty-three females were started in each pen with seven

females removed for analysis of physical attributes by 28 wk

of age. The five feed treatments were replicated four times

into blocks that minimized experimental error caused by

temperature or natural daylight gradients within blocks

while maximizing their effects among blocks. Data analysis

utilized a linear statistical model for a randomized

complete block design:

Yik = U + Ti + Bj + Eijk

where U = overall mean; Ti = fixed effect of feed treatment

and i = 1, 2, ...5; Bj = fixed effect of pen blocking and












72
j = 1, 2, ...4; and Ejik = residual effect. When differences

among treatments were obtained, comparisons among means were

made by using the Waller-Duncan K-ratio test and were

considered significant if P < .05 (SAS, 1985). Data on

flock uniformity were analyzed using the general linear

models procedure (SAS, 1985). Differences in flock

uniformity were evaluated by the F-test ratio of variances.

Pearson's product-moment correlations were determined

between hatchability and fertility, and between specific

gravity and egg weight as a measure of linear association

(SAS, 1985).



Results and Discussion

Body Weight and Uniformity

Growth of the STD fed birds throughout the rearing and

breeder periods approximated the growth curve recommended by

Arbor Acres, the primary breeder (Figure 4-2). Growth

curves resulting from all other feed treatments paralleled

STD through 62 wk of age. Some convergence in body weight

during the latter half of the production cycle did occur

especially between the -24% and -16% treatments. As

expected, the effect of feed treatment on mean body weight

at 20 wk of age was significant (Table 4-3) with the -24%

birds being 520 g lighter than STD. Uniformity, as measured

by the coefficient of variation, was significantly better

for the -8% treatment only. A possible trend towards poorer













uniformity for the most restricted birds was suspected but

not substantiated. Blair et al. (1976) and Lee et al.

(1971) reported that an apparent disadvantage to feed

restriction was a possible negative effect on flock

uniformity. The effect of feed treatment on mean body

weight was still significant through 62 wk of age and the

-24% treatment maintained a mature body weight 255 g lighter

than STD. This was similar to findings by Brody et al.

(1980) who showed that after severe feed restriction, body

weights remained about 25% lighter than the mature body

weights of a control group. Uniformity at 62 wk improved

from 20 wk levels indicating that body weight distributions

seem to stabilize as the flock achieves a mature body

weight. Shank length was significantly and permanently

decreased by the -16% and -24% treatments (Table 4-3),

which indicates a stunting of the birds mature frame size.

Flock Maturation

Feed treatment had a significant effect in delaying the

onset of flock maturity (50% production). Mean age and body

weight at 50% production for each treatment are presented in

Table 4-3. To test the hypothesis that a reduction in body

weight will delay flock sexual maturity, the dependent

variable body weight (Y, kg) was regressed on the

independent variable age (X, days) at 50% production (Figure

4-3). The resulting negative linear regression equation,

Y = 5.737 .0137 (X),
Std. Err. (.426) (.002)
Prob. .0001 .0001,














indicates that for every 13.7 g decrease in body weight,

within the range of body weights and ages at flock maturity

found in this experiment, there was a corresponding delay in

flock maturity by 1 day. The resulting negative correlation

(r = -.84) was significant and is in agreement with findings

by Pearson and Herron (1982b) who also reported a

significant negative correlation (r = -.88) between these
factors.

Mortality

Mortality was not affected by feed treatment over the

life of the flock or when analyzed by pullet or breeder hen

phase of growth (Table 4-3). The levels of mortality for

all treatments were low compared to levels commonly found in

industry. Difficulty in detecting differences among

treatments was due to high levels of between-replicate

variation. There was a trend, although not significant, for

the -24% birds to have higher mortality in the pullet

rearing period and lower mortality in the breeder hen laying

period. This trend would be in agreement with observations

made by Pym and Dillon (1969, 1974) who noted that the net

effect of high rearing and low layer mortality would be no

difference in overall mortality. Lee et al., (1971) cited

numerous reports of lower mortality during the laying period

in birds restricted during rearing. From an economic

perspective this would be an advantage due to the higher

value associated with the breeder hen.













Production Performance

The average hen-day production response to feed

treatment is illustrated in Figure 4-4. Generally, there

was a delay in sexual maturity which was proportional to the

level of feed restriction. The -16% and -24% feed

treatments had a slower rise to peak production, perhaps due

to poorer flock uniformity at that time. The production

response to all feed treatments peaked at ca. 82 to 84% and

the most restricted birds (-24%) remained at higher levels

of production from 40 through 65 weeks of age.

Average hen-day production to the common age of 64 wk

was significantly lower for the -16% and -24% treatments

(Table 4-4). These treatments were in production 8 and 15

days less than STD, respectively. However, at 64 wk of age

the -24% treatment was still at 63.4% production which was

11.5% higher than STD and represented the level of

production of STD some 10 wk earlier. This implies that

production would be likely to continue at acceptable levels

to industry for several more weeks. Moreover, there was no

significant difference in mean hen-housed production between

the -24% and STD treatments to 64 wk of age. Although

mortality was not affected by treatment the timing of

mortality relative to the production cycle was a

contributing factor to there not being differences in hen-


housed production.












76
Hen-day production of double-yolked eggs as affected by

feed treatment is illustrated in Figure 4-5. Proportional

increases in feed restriction resulted in proportional

decreases in hen-day production of double-yolked eggs. The

-24% treatment had significantly lower production of double-

yolked eggs than STD (Table 4-4). Katanbaf et al., (1989b)

showed that a standard feed restriction program will produce

fewer double-yolked eggs than an ad libitum feeding programs

by a difference of 3.5 to 4.0 times. The incidence of

double-yolked eggs has been shown to be both strain and

season related (Christmas and Harms, 1982).

Hatching eggs per hen housed did not differ

significantly among feeding programs (Table 4-4). The data

presented in Table 4-5 compares production cycles by

chronological and physiological age. Data based on

physiological age was determined by adjusting the first day

at 5% production for each replicate to be the start of the

production cycle. This adjustment permitted a direct

comparison of the production cycles by discounting treatment

effects for the delay in sexual maturity (time). Comparison

of the -24% and STD production response to feed treatment,

adjusted for time, revealed no differences between these

treatments.

Ecg Characteristics

The effect of the STD and -24% feed treatments on mean

egg weight and specific gravity during the production period













is illustrated in Figure 4-6. Generally, the -24% egg

weights were proportionately lighter and in parallel with

STD as the flock aged. By 58 wk of age egg weights

converged and no significant difference in egg weight could

be detected (Table 4-6) even though the body weights were

significantly different at this time. No differences were

found in egg weights pooled over the production cycle. The

normally arc-shaped egg weight curve appeared to flatten for

all treatments from wk 38 through 52, which corresponded to

the period of highest ambient temperatures.

Measurements on specific gravity exhibited similar but

reversed trends from egg weight. The -24% treatment had

proportionately better shell quality as specific gravity

values paralleled STD. No difference between treatments on

specific gravity or egg weight measurements could be

detected during early or late stages of the production

cycle.

The correlation coefficients between egg weight and

specific gravity are presented in Table 4-6, with their

corresponding probabilities of significance. Correlations

within treatments and pooled over the production cycle

revealed that all feed treatments had similar and highly

significant negative correlations. Correlations among

treatments characterize the age effect on these two

parameters. The positive correlation at 30 wk of age is due

to the delay in the start of the production cycle for the













-24% treatment. At this age, specific gravity values are

increasing for the -24%, whereas, the values for STD have

already peaked and are decreasing. At the end of the

production cycle, egg weights converged and an improvement

in specific gravity was found which weakened the negative

correlation between these parameters. This could be

explained, in part, by the return of cooler ambient

temperatures.

Fertility and Hatchability

Data presented in Table 4-7 demonstrate that

quantitative differences in feed restriction, even severe

feed restriction, did not have a significant effect on

fertility or total hatchability at any age. Moultry (1983)

reported lower levels of fertility and hatchability from

those birds on severe restriction during rearing and lay.

Feed Usage

Cumulative intake of feed, crude protein (CP) and

metabolizable energy (ME) are presented in Table 4-8 on a

chronological and physiological basis. Proportional

differences in quantities of feed, CP and ME for all

treatments were a result of the feed allocation program

which was used to maintain parallel growth curves. When

measured to the common chronological age of 65 wk the -24%

treatment consumed 5.02 kg less feed, .71 kg less protein,

and 15.16 Mcal less energy per hen housed for growth,

maintenance and production than did the STD. On a


















physiological basis the quantities of feed required for

growth and maintenance during the pullet phase was .68 kg

less for -24% than STD. Furthermore, the quantity of feed

consumed during the production period (breeder hen) was 4.33

kg less for -24% than STD.
The -24% treatment required numerically less feed per

dozen hatching eggs on a hen housed basis than STD (Table 4-

8). This difference was not significant due to levels of

between-replicate variation caused by the interaction of

feed treatment and environment on the initiation of

production. Moultry (1983) reported that the lowest level

of feed/dozen eggs resulted from a feeding program that was
10% above standard during rearing then 10% below standard

during lay. He found significant and proportional decreases

in feed/dozen eggs during the production period as feed was

restricted from 10% above to 15% below standard.

In summary, the results of this study indicate that

feed restriction levels below current recommendations can be

used with broiler breeder females without significantly

affecting fertility, hatchability, mortality or average egg

weight. The levels of severe feed restriction used in this

study produced a bird with a lighter mature body weight and

a smaller frame size. This bird consumed less feed without

significantly reducing the number of hatching eggs per hen

housed at a common age, when compared to birds fed on a

standard feeding program.














TABLE 4-1. Composition, calculated nutrient content and age
used for the starter and grower diets

Starter Grower Grower
21% CP 16% CP 12% CP
Ingredient (1-3 wk) (4-8/16-19 wk) (9-15 wk)
%

Yellow corn 65.53 77.43 87.25
Soy (49%) 31.15 18.84 8.80
Dical Phos 1.23 1.60 1.92
Limestone 1.09 1.13 1.03
Salt .40 .40 .40
Vit-Min** .50 .50 .50
Amprolium .05 .05 .05
BMD40 @50g/ton .05 .05 .05

Calculated Analysis*

Protein, % 21.17 16.21 12.17
ME, kcal/kg 2976 3081 3171

Contains 22% Ca and 18.5% P.

Supplied per kg of diet: 6600 IU vitamin A; 220 ICU
vitamin D3; 2.2 mg menadione dimethyl-pyrimidinol; 4.4
mg riboflavin; 13.2 mg pantothenic acid; 39.6 mg
niacin; 499 mg choline chloride; 22 mcg vitamin B12;
125 mg ethoxyquin; 60 mg manganese; 50 mg iron; 6 mg
copper; 0.198 mg cobalt; 1.1 mg iodine; 35 mg zinc.

Calculations based on 3432 and 2460 kcal/kg and 8.8 and
49% CP for corn and SBM, respectively.













TABLE 4-2. Daily nutrient intake of broiler breeders after
20 weeks of age

Nutrient Daily intake / bird

Protein, g 20.6
Sulfur amino acids, mg 754
Methionine, mg 400
Lysine, mg 938
Arginine, mg 1379
Tryptophan, mg 256
Calcium, g 4.07
Phosphorous, mg' 683
Sodium, mg 170
Vitamins" --
Energy3

1Expressed as total phosphorus.

2Levels of vitamins and trace minerals in finished feed met
minimum daily intake suggested by National Research Council
(1984).

3Diets were formulated for feed intake of 109 to 204 g/bird
per day. Examples of energy intake are 301, 398, 495, and
636 kcal per day for diets formulated for 109, 137, 164, and
204 g/bird per day feed consumed.












TABLE 4-3. Effect of feed treatment on growth, development and mortality of breeder hens

Feeding program


Variable +8% STD -8% -16% -24%

Growth

20 wk BWT, g 2261 + 26a 2103 + 23b 1935 + 19C 1751 + 23d 1583 + 21e
20 wk CV, % 14.0 13.6 11.9 16.6 15.9

62 wk BWT, g 3765 + 32a 3671 + 38b 3567 + 34C 3425 + 37d 3416 + 29d
62 wk CV, % 9.7 11.6 10.9 12.2 9.7

28 wk SHANK, mm 115.0 + .78 113.7 + .9b 114.7 + .8ab 112.5 + .9bc 110.9 + 1.1C
62 wk SHANK, mm 114.3 + .3a 114.2 + .3" 113.2 + .4b 112.1 + .4C 110.9 + .4d

Development (Flock maturation)

BWT 50% Prd., g 3157 + 28a 3049 + 36b 2964 + 37b 2809 + 8C 2648 + 42d
Age 50% Prd., d 190 + Id 197 + 1i 205 + 2b 215 i 3a 219 + 2'

Mortality

Life of flock, % 4.6 + 1.5a 5.7 + 1.8a 4.9 + 1.4a 3.8 + 1.3a 4.6 + 1.2a
Pullet phase, % 1.5 + .9" 3.8 + 2.9a 2.3 + 1.5a 1.5 + 1.5a 5.3 + .8"
Breeder phase, % 7.6 + 1.9a 7.8 + 2.0a 7.8 + 2.0a 6.2 + 1.2" 4.0 + 2.4a


BWT= Body weight, CV= Coefficient of variation, SHANK= Shank length.
* F-test ratio of variance (P<.05).
a-b Means within a row having no common superscript are significantly different (P<.05).













TABLE 4-4. Effect of feed treatment on breeder hen mean ( SEM) production performance

Feeding program


Variable +8% STD -8%

Hen-day prd
to 64 wk, % 63.5 + .6a 63.1 + .6a 63.3 +

Hen-day prd
at 64 wk, % 54.3 + 1.0c 51.9 + .8c 58.7 +

Hen-housed prd
to 64 wk, % 61.4 + .5a 59.8 + .6a 60.0 +

Hen-housed prd
at 64 wk, % 50.7 + .9cd 48.5 + 1.2d 53.4 +

Hen-day prd
DBL-YLK, % 1.23 + .1a .8 + .ab .7 +

H.E. / H.H.
to 64 wk, no. 176 + 5a 172 + 5a 172 +


a-d Means within a row having no common superscript are
H.E./H.H= Hatching eggs per hen-housed.


-16% -24%


.6a 61.0 + .7b 61.0 + .7b


1.1b 59.3 + 1.3b 63.4 + 1.la


.6a 57.9 + .7b 59.8 + .7a


.8bc 55.4 + 1.4b 61.7 + 1.4a


.Ib .5 + .1bc .4 + .1C


3a 166 + 4a 171 + 8a


significantly different (P<.05).











TABLE 4-5. Effect of feed treatment on hen-day production for chronological and
physiological ages

Chronological age Physiological age*
Age Week
(wk) +8% STD -8% -16% -24% Prd. +8% STD -8% -16% -24 %


1.7a
11.3a
36.3a
58.5a
72.9a
79.4a
81.8a
84.1
83.4a
82.1
81.6a
81.3bc
79.8b
77.0c
76.2b
75.40
72.0d
68.00
63.5d
64.0


64 54.3c


Avg.


63.5"


.8b
6.5b
21. 9b
42.1b
62.1 b
73.1b
81.la
83.5a
82.7a
83.8a
80.4a
82.9b
82.9a
80.7b
77.5b
79.1b
74.6C
67.8c
68.8c
67.9


51.90


S3bc
3.1
9.8c
23.5c
38.70
55.5c
66.6 b
76.6b
81.5a
82.7a
82.9a
85.6a
83.8a
84.0a
83.0a
79.6b
77.0b
73.9b
72.0b
71.1a

65.3a

58.7b


63.1a 63.3a


1bc
.8d
3.8d
10.7d
21.5d
35.3d
45.3c
59.80
71.6b
78.0b
82.6a
82.7b
83.0a
83.3a
82.6a
78.9b
79.6a
72.3b
73. 1ab
71.5a


00
Od
1.0d
4.3e
11.4e
25.3e
40.8d
57.5C
64.9c
71.6c
75.8c
80.00
81.9ab
84.5a
84.1a
84.6a
81.7a
77.8a
75.7a
74.1a


66.4a 65.8a

59.3b 63.4a

61.0b 61.0a


10.5a
33.9a
58.5a
72.0"
78.6a
81.1a
83.4a
83.4ab
82.4a
81.2a
82.1a
79.4b
77.9b
76.2b
75.3a
72.5a
69.4bc
62.8b
62.9b
62.7b


9.4ab
26.6b
47.01b
67.la
75.7a
82.la
82.2a
84.4a
83.0a
80.6"
83.la
83.4a
79.4ab
78.4ab
77.5a
73.3a
67.0c
68.7ab
71.0a
67.6a


7.2bc
14.7cd
31.50
49.1"
65.5b
72.4b
80.la
85.3a
82.8a
82.8a
85.4a
84.9a
83.1a
81.9a
78.1a
75.8a
70.9abc
73.9a
72.5a
69.8a


5.50
13.8d
26.3d
38.10
50.6c
64.7c
75.2b
80.2bc
82.3a
83.6a
82.1
84.9"
80.3ab
80.5a
76.1a
71.6a
73.2ab
62.2b
60.3b
67. 1ab


7.0be
18.7C
33.80
50.1b
63.1b
68.6bc
73.0b
78.6c
81.4a
83.3a
85.5a
84. a
82.8a
80.5a
75.9a
74.5a
74.6a
72.3a
71.0a
70.3a


30 62. bc 60.8c 66.2b 65.9bc 71. a

35 59.2ab 58.5b 61.8ab 60.5ab 63.9a


Avg. 66. la


66.3a 66.5a 64.7b 66.9a


* Determined by adjusting the first day of 5% production for each rep. to be the start of the production
cycle.
a-d Means within a row having no common superscript are significantly different (P<.05).




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