• TABLE OF CONTENTS
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 Front Cover
 Title Page
 Introduction
 General procedure
 Specific procedure for the individual...
 Results and discussion
 Summary
 Conclusions and recommendation...
 Acknowledgement
 Literature cited














Group Title: Bulletin - University of Florida Agricultural Experiment Station ; 706
Title: Feed restriction of swine during the finishing period
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Permanent Link: http://ufdc.ufl.edu/UF00027637/00001
 Material Information
Title: Feed restriction of swine during the finishing period
Series Title: Bulletin - University of Florida Agricultural Experiment Station ; 706
Physical Description: Book
Language: English
Creator: Wallace, H. D.
Palmer, A. Z.
Carpenter, J. W.
Combs, G. E.
Publisher: Agricultural Experiment Stations, Institute of Food and Agricultural Sciences, University of Florida,
Publication Date: 1966
 Record Information
Bibliographic ID: UF00027637
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.

Table of Contents
    Front Cover
        Page 1
    Title Page
        Page 2
    Introduction
        Page 3
        Page 4
        Page 5
    General procedure
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
    Specific procedure for the individual experiments
        Page 11
        Page 12
    Results and discussion
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
        Page 18
        Page 19
        Page 20
        Page 21
        Page 22
        Page 23
        Page 24
        Page 25
        Page 26
        Page 27
        Page 28
    Summary
        Page 29
        Page 30
    Conclusions and recommendations
        Page 31
    Acknowledgement
        Page 32
    Literature cited
        Page 33
        Page 34
Full Text


'I,
a








CONTENTS

Page
Introduction ----------- 3

General Procedure --------- 6

Specific Procedure for the Individual Experiments 11

Results and Discussion 13

Experiment 1 ------- --- -----_ 13

Experiments 2 and 3 16

Experiment 4 ---_------ -- 18

Experiment 5 -----__ 22

Experiments 6 and 7 --. ..-.._ .....--... 24

Summary -- ------_ 29

Conclusions and Recommendations ---._.. .. 31

Acknowledgments ... ... .. ... ...----------------__... 32

Literature Cited -------------_33









FEED RESTRICTION OF SWINE DURING
THE FINISHING PERIOD


H. D. Wallace, A. Z. Palmer, J. W. Carpenter, and G. E. Combs 1


INTRODUCTION
The idea of restricting the feed intake of swine during the
finishing period is not new. European countries have practiced
this procedure for many years in an effort to produce top quality
pork products. The feasibility of restricting feed has been in-
vestigated in the United States with rather indecisive results.
As would be expected, gains are slower and the feeding period
is extended. In most experiments a definite improvement in the
carcass lean-fat ratios has been observed. However, the import-
ance of this improvement in terms of increased returns to the
producer has been limited. Consequently, feed restriction has
never been widely adopted by the American swine producer.
Rapid gains and use of the labor-saving self feeder have been
overriding considerations.
In recent years the ever-pressing need for improved feed
utilization, the emphasis on leaner pork cuts, and the develop-
ment of automated equipment suitable for use in restricted feed-
ing programs have kindled much new interest in the procedure.
There is no question as to the sensitivity of swine to dietary
manipulations insofar as carcass composition is concerned. The
striking changes which normally occur in the carcass composi-
tion of pigs from birth to market weight are amply described
in animal science literature. These changes are graphically
portrayed in Figure 1. It can be seen that late in the finishing
period, between the weights of 150 and 250 pounds, gains are
normally relatively much higher in fat. One of the main objec-
tives of feed restriction is to alter the composition of carcass
gains during this period, causing an increase in the relative
amount of lean meat and a reduction in the amount of waste fat.
A second important objective of restricted feeding is to improve
the efficiency of live weight gains. In principle this would seem
simple enough, since it is well recognized that water and protein
1 Animal Nutritionist, Meats Scientist, Assistant Meats Scientist, and
Associate Animal Nutritionist, Animal Science Department, Gainesville.







Florida Agricultural Experiment Stations


are less expensively incorporated into body tissue than fat.
However, it is on this issue of feed conversion that much con-
troversy is presently centered regarding restricted feeding.
Several factors degree of restriction, composition of diet,
methods of feeding, sex, and the genetic makeup of the animals
involved appear to influence feed utilization under limited
feeding regimes.



BODY COMPOSITION CHANGE OF PIGS
DURING GROWING FINISHING PERIOD
40
Protein
34
D Water
30 Fat 28
i 24 23

zE20 19
< 17 16

I I
10i



50-100 100-150 150-200 200-250
EMPTY BODYWEIGHT, LB.

Figure 1.-The average gains of typical pigs between 50 and 100 pounds
are represented by approximately 48 percent water, 34 percent fat, 14 percent
protein, 6 percent ash, and small amounts of carbohydrates. Late in the finishing
period between the weights of 150 and 200 pounds, gains are represented by
approximately 32 percent water, 56 percent fat, 10 percent protein, 4 percent
ash, and small amounts of carbohydrates. (Adapted from United States Depart-
ment of Agriculture Yearbook, 1939.)


The scientific literature on the feed restriction of swine is
voluminous. Only a few of the more pertinent and illustrative
papers will be cited. A severe restriction of feed intake of swine
results in a marked reduction in backfat thickness as shown
by the studies of McMeekan (15)2 and Calloway (5). A severe
restriction also produces soft carcasses, as reported by Hilditch
SNumbers in parentheses refer to Literature Cited.







Feed Restriction of Swine


et al. (11) and lowers market grade as observed by Crampton
(6). Many studies, in which moderate restriction has been im-
posed, have reported significant reductions in backfat with no
serious detrimental effects on carcass firmness (3, 4, 7, 8, 9, 14,
16, 17, 20, 21, 23, 25). As the percentage of fat trim decreased
in these studies, a relative increase in the percentage of lean
cut yields was observed. There is generally good agreement
among the reports concerning the effect of restricted feeding
on carcass characteristics. The agreement relative to feeding
efficiency is not so good. A depression in feeding efficiency under
restricted feeding regimes has been reported by Tribble and
Holck (22), Thrasher (20), and Geurin et al. (10). Conversely,
Becker et al. (1), Hillier et al. (12), and Koch (13) have report-
ed an improvement in feed utilization under restricted feeding
programs.
One very worthwhile practical point in favor of feed restric-
tion is that the procedure can readily eliminate most feed wast-
age. This, of course, can also be accomplished under carefully
managed full-feeding programs. Nevertheless, the elimination
of feed wastage has a certain amount of appeal to producers and
thus is a point to be considered.
Feed restriction may be accomplished by three general pro-
cedures. In all cases the object is to restrict energy and cause
energy to be the first limiting dietary factor. These procedures
may be described as follows:

1. Increase fiber content of diet.-This procedure permits
the use of self feeding. The main requirement is to include in
the diet a low energy fibrous ingredient at levels which slow
weight gains, causing a more desirable deposition of lean and
fat. Recent experiments using this method have revealed an
excessive feed cost (1, 24), probably because of the added cost
of grinding and handling the diluent material and a greater
tendency toward feed wastage.

2. Feed a certain percentage of a full-feed allowance.-
Usually a 10 to 20 percent restriction is imposed under this
procedure. It is necessary to adjust the intake upward regularly
in accordance with the weight changes of the animal in order
to maintain the predetermined level of intake. At best this pre-
determined percentage of a full-feed intake can be only an
estimate and is a drawback of such a procedure.







Florida Agricultural Experiment Stations


3. Feed a constant level of feed throughout the entire finish-
ing period.-Under this procedure a predetermined daily feed
allowance is selected and adhered to throughout the finishing
period. Thus the method imposes a constantly increasing level
of restriction as the animal progresses toward the finishing
weight. In theory, this would seem suitable from the standpoint
of desirable lean tissue development, since the excessive and
undesirable fat deposition occurs during the latter days of the
finishing period. This method also has a simplifying effect on
feedlot management and is readily adapted to mechanization,
as the amount of feed offered remains the same throughout the
feeding period. It was this procedure that was followed in the
present investigation.
The experiments conducted during the course of this investi-
gation were designed to obtain information in three general
areas:
1. The influence of feed restriction on rate of gain and effi-
ciency of feed conversion.
2. The influence of feed restriction on the desirability of
carcasses produced with special emphasis on the tenderness of
pork chops.
3. Factors which influence the response to feed restriction.


GENERAL PROCEDURE
Animals.-The experimental pigs were produced at the
Florida Experiment Station Swine Unit and were three-breed
crossbreds (Landrace-Duroc x Hampshire) sired by two litter-
mate Hampshire boars (see Figure 2), with the exception of 12
pigs fed in Lot 1 of Experiment 5. These twelve pigs were two-
breed crossbreds (Landrace x Duroc). The pigs were weaned
at two weeks of age and fed and managed in a routine manner
during the growing period. No feed restriction was imposed
prior to the initiation of the experiments.

Allotment.-Outcome groups were formed on the basis of
weight, sex, and litter, and these groups were randomly assigned
to experimental treatments for the various experiments.

Feeding procedure.-All feed was offered in dry meal form.
Full-fed pigs ate from self-feeders. Restricted pigs were allowed







Feed Restriction of Swine


"' ftl'*1kk


Figure 2.-The above animals are three-breed crossbreeds (Landrace-Duroc x
Hampshire) typical of those used in the study.

approximately 5 pounds of feed per head per day divided evenly
between morning and evening feedings. Restricted pigs were
hand fed in troughs. The feed mixture was the same for full-fed
and restricted pigs. Automatic waterers provided a continuous
supply of drinking water.
Feed mixtures.-Composition of the feed mixtures used in
the various experiments is shown in Table 1.
Weighing.-All animals were weighed at the start, at the
end of four weeks of the experiment, and at intervals thereafter
until the desired final weight was attained. All animals were
individually weighed off experiment for slaughter at 200 5
pounds. In order to minimize the variation in weight due to fill
between full-fed and restricted pigs all animals were weighed
off experiment at approximately 9 a.m. or about one hour after
the restricted pigs had consumed their morning feed. A check
of this procedure indicated that "fill" was almost identical for
the two feeding methods.
Slaughter and carcass measurements. The pigs were
slaughtered and dressed packer style for carcass study. Carcass










Table 1.-Percent composition of feed mixtures used in the various experiments.

Expts. 6 & 7
Ingredient Expt. 1 Expts. 2 & 3 Expt. 4 Expt. 5 High Low
Protein Protein
Ground yellow corn 80.35 80.25 80.25 80.20 77.33 91.55
Soybean oilmeal (50% protein) 17.00 17.00 17.00 17.00 20.00 5.50
Ground limestone 1.00 1.00 1.00 1.00 1.50 1.80
Steamed bonemeal 1.00 1.00 1.00 1.00 0.50 0.50
Iodized salt 0.50 0.50 0.50 0.50 0.50 0.50
Trace minerals a 0.50 0.50 0.05 0.05 0.05 0.05
B-vitamin supplement 0.10 b 0.10 b 0.10 e 0.10 d 0.10 d 0.10 d
Vitamin Bi supplement e -0.05 0.05 0.05
Antibiotic supplement -0.10 f 0.10 f 0.10 -

Calculated protein level, % 15.75 15.75 15.75 15.75 17.00 11.00

a MnSO, 22.5%, FeSO, 35.0%, CuSO, 1.89%, CoSO 0.498%, ZnSO, 10.0%, KSO, 1.67%, and CaCO, 28.442%.
b Contained 4.5 mg vitamin B,, 2000 mg riboflavin, 300 pantothenic acid, 9000 mg niacin, and 9800 mg choline chloride per pound.
c Contained 2000 mg riboflavin, 4000 mg pantothenic acid, 9000 mg niacin, and 10,000 mg choline chloride per pound.
d Contained 8000 mg riboflavin, 14,720 mg pantothenic acid, 36,000 mg niacin, and 40,000 mg choline chloride per pound.
e Contained a minimum of 20 mg vitamin B. per pound.
f Contained a minimum of 10 gm tylosin per pound.
g Contained a minimum of 10 gm terramycin per pound.







Feed Restriction of Swine


weights and measurements were taken after the carcasses had
been chilled for 48 hours at 34 to 36 F. Length of carcass was
obtained by a measurement from the anterior edge of the aitch
bone (pelvis) to the anterior edge of the first rib. Backfat thick-
ness was calculated as an average of measurements taken at the
first rib, last rib, and last lumbar vertebra. A tracing was made
of the perimeter of the longissibms dorsi muscle (loin eye), ex-
posed by cutting the loin perpendicular to the vertebral column
equidistant between the tenth and eleventh ribs. The area of
the loin eye muscle was then determined by use of a compensat-
ing polar planimeter. The carcasses were broken down by a
standard procedure as described in the proceedings of the Fourth
Annual Reciprocal Meats Conference (18).

Tenderness determinations.-One loin from each carcass was
cut between the tenth and eleventh ribs and the blade end,
wrapped, frozen, and stored at 0 F. for later testing. For ten-
derness testing three adjacent 1-inch thick chops were removed
from each loin segment with the first chop removed containing
the tenth rib. The chops were defrosted at 34 to 360 F. over-
night. Two chops were prepared for a four-member trained
taste panel by removing the loin eyes from the chops, placing
them in covered petri dishes, and cooking in a preheated 350
F. oven for 30 minutes. The cooked chops were cooled at room
temperature and single 12 inch cores were removed for Warner-
Bratzler shear evaluation. Each core was sheared twice. The
four shear values obtained were averaged to give the shear ten-
derness score for each animal. The first chop cut from the loin
segment was evaluated for tenderness by two of the panel mem-
bers and the second chop by the other two panel members. The
four determinations of the panel members were averaged, and
that value represented the panel tenderness score for e a c h
animal.
The third chop was fried for 5 minutes in deep fat which
had been preheated to 350 F. A single 1 2 inch core was taken
from the cooled chop and sheared twice by the Warner-Bratzler
device, and the average of the two values represented the fry-
chop tenderness score.

In Experiments 6 and 7, both panel evaluations and shear
evaluations were made on the fried chops.







Florida Agricultural Experiment Stations


Description of other measurement criteria


pounds chilled dressed carcass
Dressing percent = X 100
pounds slaughter weight


pounds fresh liver
Percent liver = pounds fresh liver X 100
pounds chilled dressed carcass


pounds combined trimmed hams,
Percent loins, picnic shoulders, Boston butts
4 lean cuts = X 100
pounds chilled dressed carcass


Marbling score.-Scores were coded from 0 to 33. Devoid =
0, practically devoid 1-3, traces = 4-6, slight = 7-9, Small =
10-12, modest = 13-15, moderate = 16-18, slightly abundant =
22-24, abundant 25-27, very abundant = 28-30, and extremely
abundant = 31.33. Visual observations were made on the cross
section of the longissimus dorsi (eye of the pork chop) exposed
by cutting midway between the tenth and eleventh ribs.

Carcass firmness score.-Firmness was determined after 48
hours of chill at 34 to 36 F. by manual palpation of the carcass.
Scores were coded from 1 to 5. 1 = hard, 2 = medium hard,
3 = medium soft, 4 = soft, and 5 = oily.

Panel tenderness score.-Scores were coded from 1 to 9.
1 = too tough to be edible, 2 = extremely tough, 3 = very
tough, 4 = below average tenderness, 5 = average tenderness,
6 = above average tenderness, 7 = very tender, 8 = extremely
tender, and 9 = mushy. As the score increased, tenderness
increased.

Shear tenderness score.-In contrast to the panel tenderness
score, the shear tenderness score as recorded by the Warner-
Bratzler device decreased with increased tenderness.

Statistical analysis.-Growth and carcass data from all
experiments were statistically evaluated according to analysis
of variance methods outlined by Snedecor (19).







Feed Restriction of Swine


SPECIFIC PROCEDURE FOR THE
INDIVIDUAL EXPERIMENTS
Experiment 1.-Sixty-four pigs were allotted to eight lots of
eight pigs each. Two lots of barrows and two lots of gilts were
full-fed, and two lots of each sex were restricted. The treatment
assignments are shown in Table 2. The pigs were group-fed
in concrete confinement. The experiment was initiated Novem-
ber 1, 1962, and the final pig was slaughtered January 15, 1963.
Experiment 2.-Forty-eight pigs were divided into two lots
of 24 pigs each. Each lot contained 15 gilts and 9 barrows. The
treatment assignments are shown in Table 4. The pigs were
group-fed in small pasture lots. The experiment was initiated
September 4, 1962, and the final pig was slaughtered November
29, 1962.
Experiment 3.-Forty-eight pigs were divided into two lots
of 24 pigs each. Each lot contained 9 gilts and 15 barrows. The
treatment assignments are shown in Table 4. The pigs were
group-fed in small pasture lots. The experiment was initiated
on December 22, 1962, and the final pig was slaughtered March
4, 1963.
Experiment 4.-Forty-eight pigs were divided into four
groups of 12 pigs each. Each group consisted of 6 gilts and 6
barrows. The treatment assignments are shown in Table 7. Two
groups, one full-fed and one restricted, were individually penned
and fed in small dirt lots. The other two groups, one full-fed
and one restricted, were group-fed in dirt lots. The experiment
was initiated April 4, 1963, and the final pig was slaughtered
on July 10, 1963.
Experiment 5.-Sixty pigs were divided into five groups of
12 pigs each and group-fed in dirt lots. Method of feeding, breed
composition, starting weights, and sex are shown in Table 9.
The experiment was initiated October 5, 1963, and the final pig
was slaughtered January 28, 1964.
Experiment 6.-Forty pigs were divided into four groups of
10 pigs each and individually fed and housed in concrete con-
finement. Each group consisted of 5 barrows and 5 gilts. The
treatment assignments are shown in Table 10. Two groups were
full-fed, one on a diet containing 17 percent crude protein and


11







Table 2.-Summary of fedlot performance and carcass data for individual lots (Experiment 1).a
Lot number 1 2 3 4 1-A 2-A 3-A 4-A
Feed level Restricted Full Restricted Full Restricted Full Restricted Full
Sex Gilts Gilts Gilts Gilts Barrows Barrows Barrows Barrows
Number of pigs 8 8 8 8 8 8 8 8
Initial wt., lb. 100.1 99.8 100.0 99.3 100.8 99.6 99.8 99.8
Slaughter wt., lb. 99.4 199.0 199.3 200.8 197.6 201.9 197.5 202.9
Number days on feed 73.6 57.7 69.4 57.7 72.8 56.2 72.9 54.3
Daily gain, lb.
First 4 weeks 1.50 1.95 1.54 1.92 1.38 2.00 1.45 2.04
Entire period 1.35 1.72 1.43 1.76 1.33 1.82 1.34 1.90
Daily feed intake, lb. 4.97 6.02 5.09 6.28 5.09 7.01 5.03 7.26
Feed per lb. gain, lb. 3.68 3.50 3.56 3.57 3.83 3.85 3.75 3.82
Dressing percent 70.55 73.85 71.21 73.28 70.76 72.54 70.04 72.26
Percent liver 2.25 2.35 2.36 2.26 2.34 2.48 2.29 2.44
Carcas length, in. 30.18 29.96 29.94 30.30 29.62 29.42 29.72 29.44
Backfat thickness, in. 1.08 1.19 1.14 1.25 1.16 1.38 1.16 1.40
Carcass firmness score 2.62 2.00 2.75 1.87 2.62 1.75 2.75 1.25
Loin eye area, sq. in. 3.69 3.85 3.85 3.63 3.50 3.35 3.49 3.16
Wt. of hams, lb. 28.84 28.95 28.95 27.78 26.64 26.90 28.37 26.17
Wt. of loins, lb. 23.00 23.74 23.68 22.79 21.68 21.92 22.14 20.80
Wt. of picnics, lb. 13.62 13.32 13.56 13.46 13.25 13.43 13.83 12.71
Wt. of butts, lb. 10.20 10.38 10.18 9.79 9.88 9.75 10.33 9.49
Percent 4 lean cuts 53.80 52.02 53.85 50.26 52.05 49.28 53.91 47.33
Marbling score 9.12 10.31 8.94 12.95 11.69 13.87 9.75 12.94
Tenderness of chops
Panel 5.88 5.84 6.09 6.09 5.75 5.53 5.75 6.31
Shear 7.52 8.15 6.78 7.25 7.75 7.99 7.45 6.42
Fry chop 9.19 9.30 7.83 8.73 8.64 9.13 8.06 8.00
a Please refer to "General Procedure" for details concerning the various measurement criteria.







Feed Restriction of Swine


one on a diet containing 11 percent crude protein. Two groups
were restricted, one fed a 17 percent protein diet and the other
an 11 percent protein diet. The experiment was initiated Febru-
ary 15, 1964, and the final pig was slaughtered May 18, 1964.

Experiment 7.-Forty pigs were divided into four groups of
10 pigs each and group fed in dirt lots. Each group consisted
of four barrows and six gilts. The treatment assignments are
shown in Table 11. Two groups were full-fed, one on a diet con-
taining 17 percent crude protein and one on a diet containing 11
percent crude protein. Two groups were restricted, one fed a
17 percent protein diet and the other an 11 percent protein diet.
The experiment was initiated February 20, 1964, and the final
pig was slaughtered June 1, 1964.


RESULTS AND DISCUSSION

Experiment 1

Summaries of feedlot performance and carcass data are
presented for the individual lots in Table 2 and for the main
treatment variables in Table 3. The comments to follow will be
concerned with the overall summation given in Table 3.

Level of feeding effect.-Pigs full-fed gained an average of
1.80 pounds per head per day compared to 1.36 for the pigs
limited to 5 pounds of feed per day. This difference was highly
significant (P < .01). It is of interest to note that during the
first four weeks of the experiment both groups gained faster
than during the terminal phase of the experiment. As a result
of the slower gains made by the restricted pigs, an average of
approximately 17 days additional time was required to reach
slaughter weight when the final weight of the restricted pigs
was projected to that of the full-fed pigs. The amount of feed
required per pound gain was approximately the same for the
restricted and full-fed pigs (3.70 vs. 3.68). Work at the Illinois
station (1) has demonstrated about a 10 to 15 percent saving
in feed with a feed restriction method similar to that employed
in this experiment. In the Illinois work the pigs were individually
fed, the feed was wetted, and the animals were shrunk prior
to tabulating final weights. Any one or all of these factors plus
the difference in the type of hogs used may have contributed to










Table 3.-Summary of fi


Comparison
Number of pigs
Initial wt., lb.
Slaughter wt., lb.
Number days on feed
Daily gain, lb.
First 4 weeks
Entire period
Daily feed intake, lb.
Feed per lb. gain, lb.
Dressing percent
Percent liver
Carcass length, in.
Backfat thickness, in.
Carcass firmness score
Loin eye area, sq. in.
Wt. of hams, lb.
Wt. of loins, lb.
Wt. of picnics, lb.
Wt. of butts, lb.
Percent 4 lean cuts
Marbling score
Tenderness of chops
Panel
Shear
Fry chop


eedlot performance and carcass data by main treatment variables (Experiment 1).a
Level of Feeding Effect Sex Effect Statistical Significance
Restricted Full Gilts Barrows Level of Feeding Sex


32
100.2
198.4
72.2

1.47
1.36
5.03
3.70
70.64
2.31
29.87
1.15
2.69
3.63
28.20
22.63
13.57
10.15
53.40
9.87

5.87
7.37
8.43


32
99.6
201.1
56.4

1.98
1.80
6.62
3.68
72.98
2.38
29.78
1.30
1.72
3.50
27.48
22.31
13.23
9.85
49.72
12.52

5.94
7.45
8.79


32
99.8
199.6
64.6

1.73
1.56
5.58
3.58
72.22
2.30
30.10
1.15
2.31
3.76
28.63
23.30
13.49
10.14
52.48
10.33

5.96
7.43
8.76


32
100.0
200.0
64.0

1.72
1.60
6.10
3.81
71.40
2.39
29.55
1.30
2.09
3.38
27.04
21.64
13.31
9.86
50.64
12.06

5.84
7.40
8.46


a Please refer to "General Procedure" for details concerning the various measurement criteria.
* Significantly different (P<.05)
** Significantly different (P<.01)
NS Not significant







Feed Restriction of Swine


results relative to feed conversion. It did appear that in the
present study the five pounds of feed represented too severe a
restriction for the animals, particularly during the final days
of the experiment.
Full-fed pigs dressed 72.98 percent compared to 70.64 percent
for the restricted pigs. This difference was highly significant
(P < .01) and probably reflects mainly the difference in finish.
Backfat thickness was significantly less for the restricted pigs
(1.15 vs. 1.30). Carcass length favored the restricted pigs by
about 0.1 inch, but the difference was not significant. Carcass
firmness scores indicated a highly significant difference in favor
of the full-fed pigs. Many of the restricted carcasses were soft
and exhibited a watery condition in the lean meat. The average
loin eye area was somewhat greater for the restricted pigs, but
the difference was not statistically significant. The average
weight of each of the four lean cuts favored the restricted
group, and the difference was highly significant (P < .01) for
the hams. There was a very marked difference in percent four
lean cuts which favored the restricted pigs (53.40 vs. 49.72).
This difference was highly significant (P < .01). Full-fed pigs
yielded a slightly greater but non-significant percent liver. Differ-
ences in tenderness of chops due to level of feeding were not
significant.
Sex effect.-Barrows gained slightly faster than gilts during
the entire trial, but this difference was non-significant. Gilts
gained more efficiently (P < .05) than barrows (3.50 pounds
feed per pound gain compared to 3.81). Dressing percent favored
the gilts, but the difference was not statistically significant.
Carcasses from gilts averaged 30.10 inches long, while those
from barrows averaged 29.55 (P < .01). Gilt carcasses carried
1.15 inches of backfat compared to 1.30 for barrows (P < .01).
Carcasses from barrows were somewhat firmer, but this was a
nonsignificant difference. Gilt carcasses showed highly signif-
icant advantages for loin eye area, weight of hams, weight of
loins, and percent four lean cuts (P < .01). Chops from barrows
tended to be slightly tenderer than those from gilts but the
difference was not significant.
A significant sex and feed level interaction was revealed in
the data (P < .05); gilts gained relatively faster on the re-
stricted feeding program, whereas barrows gained relatively
faster on the full-feeding regime.







Florida Agricultural Experiment Stations


Experiments 2 and 3
A summary of feedlot performance and carcass data for
Experiments 2 and 3 is presented in Table 4. A summary of
the sex effect under each level of feeding for Experiments 2 and
3 combined is presented in Table 5.
In both experiments, full-fed pigs gained significantly faster.
Full-fed pigs required considerably less feed per pound of gain.
Approximately 20 and 23 days more feeding time were required
by the restricted pigs in Experiments 2 and 3, respectively, to
reach the same projected finished weight as the full-fed pigs.
In Experiment 2 restricted pigs, contrary to expectations,
dressed higher than full-fed pigs. This result was probably due
to variations in fill which affected slaughter weight. Normally,
full-fed pigs would be expected to show a higher dressing percent
because of a higher degree of finish. This was true in Experi-
ment 3 and ensuing experiments. Carcass length was not sig-
nificantly affected by feeding level in either experiment. Backfat
thickness was significantly less (P < .01) for restricted pigs
in both experiments. Carcasses from full-fed pigs were signifi-
cantly firmer. Loin eye area measurements were greater for
restricted pigs in both experiments, but the differences were
not statistically significant. Percent four lean cuts was markedly
greater for the restricted pigs, and the difference was highly
significant (P < .01) in Experiment 3. In both experiments the
percent liver was significantly greater (P < .01) for the full-fed
pigs, indicating that liver tissue was stimulated and developed
to a greater extent, probably as a result of having to metabolize
more food material. Or perhaps more nutrient substances such
as glycogen were being held as reserve in the liver tissue of the
full-fed pigs, accounting for the greater liver weight. Significant
differences in chop tenderness were observed in Experiment 2
in favor of the full-fed pigs.
The data presented in Table 5 indicate that both sexes are
influenced in a similar manner by feed restriction. Barrows
tended to improve somewhat more in percent four lean cuts
as a result of feed restriction, but still remaining inferior to gilts
in this regard.
Table 6 presents a combined summary for Experiments 2 and
3 as to main treatment variables. In general, the overall effects
were quite similar to those observed in Experiment 1. Full-fed








Table 4.-Summary of feedlot performance and carcass data for individual lots (Experiments 2 and 3).a

Statistical Significance
Experiment 2 Experiment 3 Expe-
Comparin R d Fl R d Fl Experi- Experi-
Comparison Restricted Full Restricted Full meant 2 ment 3


Number of animals
Initial wt., lb.
Slaughter wt., lb.
Number days on feed
Daily gain, lb.
Daily feed intake, lb.
Feed per lb. gain, lb.
Dressing percent
Percent liver
Carcass length, in.
Backfat thickness, in.
Carcass firmness score
Loin eye area, sq. in.
Wt. of hams, lb.
Wt. of loins, lb.
Wt. of picnics, lb.
Wt. of butts, lb.
Percent 4 lean cuts
Marbling score
Tenderness of chops
Panel
Shear
Fry chop


24
99.7
198.8
68.6
1.46
5.05
3.46
69.97
2.57
30.14
1.04
2.38
4.05
28.04
23.79
13.58
10.23
54.44
8.38

5.57
8.56
8.79


24
99.6
205.9
52.7
2.03
6.78
3.34
68.55
3.10
30.04
1.18
1.92
3.71
27.96
22.79
13.74
10.12
52.94
12.06

6.00
7.48
8.28


24
101.7
194.0
74.6
1.27
5.13
4.04
68.77
2.35
29.64
1.05
2.58
3.93
27.06
23.29
13.24
10.02
55.17
11.83

5.85
8.23
8.07


24
101.2
196.9
53.0
1.84
6.53
3.55
69.60
2.57
29.39
1.25
1.88
3.87
26.28
22.71
13.63
10.24
53.18
12.98

6.00
8.07
8.20


a Please refer to "General Procedure" for details concerning the various
* Significantly different (P<.05)
** Significantly different (P<.01)
NS Not significant


measurement criteria.







Florida Agricultural Experiment Stations


Table 5.-The relationship of sex to the influence of feed restriction on feedlot
performance and carcass characteristics (Experiments 2 and 3 com-
bined).a

Restricted Full-fed
Comparison Gilts Barrows Gilts Barrows

Number of animals 24 24 24 24
Initial wt., lb. 98.6 102.8 98.9 101.8
Slaughter wt., lb. 196.9 195.9 202.0 200.8
Number days on feed 72.8 67.5 53.4 50.8
Daily gain, lb. 1.35 1.38 1.93 1.95
Dressing percent 69.72 69.01 68.90 69.25
Percent liver 2.48 2.46 2.85 2.81
Carcass length, in. 29.94 29.84 29.92 29.51
Backfat thickness, in. 1.00 1.10 1.14 1.30
Carcass firmness score 2.71 2.25 2.13 1.67
Loin eye area, sq. in. 4.31 3.66 3.95 3.68
Wt. of hams, lb. 28.14 26.95 27.80 26.44
Wt. of loins, lb. 24.31 22.78 23.42 22.09
Wt. of picnics, lb. 13.52 13.31 13.86 13.51
Wt. of butts, lb. 10.28 9.96 10.22 10.14
Percent 4 lean cuts 55.54 54.07 54.10 52.03
Marbling score 9.65 10.56 11.69 13.36
Tenderness of chops
Panel 5.80 5.62 5.89 6.10
Shear 8.04 8.75 7.98 7.55
Fry chop 8.11 8.48 8.53 7.95
a Please refer to "General Procedure" for details concerning the various measurements
criteria.


animals gained faster, and yielded firmer carcasses with more
backfat, but yielded a lower percent of lean meat as indicated
by smaller loin eye areas and less percent four lean cuts. Gilts
yielded more lean meat but gilt carcasses were not as firm as
barrow carcasses. The overall beneficial influence of feeding
level on chop tenderness was significant (P < .05).


Experiment 4

This experiment was designed primarily to obtain informa-
tion on the influence of feeding methods (individual vs. group)
on the response to feed restriction. Results of the experiment
are summarized in Tables 7 and 8. Data for the individual lots
are shown in Table 7. The main treatment effects and informa-
tion on statistical analysis are presented in Table 8. One of the







Table 6.-Summary of feedlot performance and carcass data by main treatment variables (Experiments 2 and 3 combined).a
Level of Feeding Effect Sex Effect Statistical Significance
Comparison Restricted Full Gilts Barrows Level of Feeding Sex
Number of animals 48 48 48 48 -
Initial wt., Ib. 100.7 100.4 98.8 102.3 -
Slaughter wt., lb. 196.4 201.4 199.5 198.4 -
Number days on feed 69.9 52.1 61.4 57.5 -
Daily gain, lb. 1.37 1.94 1.64 1.67 ** NS
Daily feed intake, lb. 5.09 6.66 -
Feed per lb. gain, lb. 3.75 3.45 -- -
Dressing percent 69.37 69.08 69.31 69.13 NS NS
Percent liver 2.47 2.83 2.67 2.64 ** NS
Carcass length, in. 29.89 29.72 29.93 29.68 NS NS t
Backfat thickness, in. 1.05 1.22 1.07 1.20 ** **
Carcass firmness score 2.48 1.90 2.42 1.96 ** **
Loin eye area, sq. in. 3.99 3.81 4.13 3.67 **
Wt. of hams, lb. 27.55 27.12 27.97 26.70 -
Wt. of loins, lb. 23.55 22.76 23.87 22.44
Wt. of picnics, lb. 13.42 13.69 13.69 13.41
Wt. of butts, lb. 10.12 10.18 10.25 10.05 -
Percent 4 lean cuts 54.81 53.06 54.82 53.05 ** **
Marbling score 10.11 12.53 10.67 11.96 NS NS
Tenderness of chops
Panel 5.71 6.00 5.85 5.86 NS
Shear 8.40 7.77 8.01 8.15 NS
Fry chop 8.30 8.24 8.32 8.22 NS NS
a Please refer to "General Procedure" for details concerning the various measurement criteria.
* Significantly different (P<.05)
* Significantly different (P<.01) -
NS Not significant (o








Florida Agricultural Experiment Stations


Table 7.-Feedlot performance and carcass data as influenced by level and
method of feeding for the individual lots (Experiment 4).a

Lot Number 1 2 3 4
Feed Level Restricted Full Restricted Full
Feeding Method Individual Individual Group Group

Number of animals 12 12 12 12
Initial wt., lb. 97.0 96.9 97.3 97.0
Slaughter wt., lb. 198.9 199.6 197.5 202.6
Number days on feed 71.8 62.2 71.1 62.9
Daily gain, lb.
First 4 weeks 1.45 1.65 1.45 1.45
Entire period 1.42 1.65 1.41 1.68
Daily feed intake, lb. 4.94 5.31 4.99 6.03
Feed per lb. gain, lb. 3.48 3.22 3.54 3.59
Dressing percent 69.51 69.54 68.38 69.04
Percent liver 2.28 2.49 2.44 2.61
Carcass length, in. 30.53 30.50 30.62 30.22
Carcass firmness score 1.67 2.25 2.00 2.00
Loin eye area, sq. in. 3.87 3.89 3.83 3.74
Wt. of hams, lb. 29.26 29.34 27.45 28.80
Wt. of loins, lb. 23.08 23.12 22.89 22.39
Wt. of picnics, lb. 13.98 13.94 13.45 13.81
Wt. of butts, lb. 10.32 10.47 9.96 10.06
Backfat thickness, in. 1.08 1.10 1.05 1.21
Percent 4 lean cuts 55.42 55.41 54.17 53.71
Marbling score 11.88 10.12 12.29 13.13
Tenderness score of chops 8.87 6.93 9.05 7.17

a Please refer to "General Procedure" for details concerning the various measurements
criteria.


most interesting results of this experiment concerns feed con-
versions. Both restricted pigs and full-fed pigs, when individu-
ally fed, converted feed to gain more efficiently than when group
fed (Table 7). This was particularly pronounced for the full-fed
group.

Level of feeding effect.-As would be expected, full-fed pigs
gained significantly faster and required less time to reach final
slaughter weight. The feed required per unit of gain on an
overall basis (Table 8) favored the full-fed pigs (3.51 vs. 3.41).
Differences in dressing percent, carcass length, carcass firmness
score, percent four lean cuts, and loin eye area were not statis-
tically significant. The limited fed pigs were leaner, as indicated
by less backfat (P < .01). Full-fed pigs yielded a higher percent-








Table 8.-Feedlot performance and carcass data as influenced by main treatment variables (Experiment 4).a


Feed Level
Restricted Full


Comparison


Feeding Method
Individual Group


Sex
Barrows Gilts


Statistical Significance
Feed Feeding Sex
Level Method


Number of animals
Initial wt., lb.
Slaughter wt., lb.
Number days on feed
Daily gain, lb.
First 4 weeks
Entire period
Daily feed intake, lb.
Feed per lb. gain, lb. b
Dressing percent
Percent liver
Carcass length, in.
Backfat thickness, in.
Carcass firmness score
Loin eye area, sq. in.
Wt. of hams, lb.
Wt. of loins, lb.
Wt. of picnics, lb.
Wt. of butts, lb.
Percent 4 lean cuts
Marbling score
Tenderness score of chops
(shear)


24
97.1
198.2
71.7

1.45
1.41
4.95
3.51
68.94
2.36
30.58
1.06
1.84
3.85
28.36
22.99
13.73
10.14
54.79
12.09
8.96


24
96.9
201.1
62.4

1.55
1.67
5.69
3.41
69.29
2.55
30.36
1.16
2.12
3.82
29.07
22.76
13.88
10.27
54.56
11.63
7.05


24
96.9
199.2
66.4

1.55
1.54
5.16
3.35
69.53
2.38
30.51
1.09
1.96
3.88
29.30
23.10
13.96
10.40
55.42
11.00
7.90


24
97.2
200.1
66.8

1.45
1.54
5.48
3.56
68.71
2.53
30.42
1.13
2.00
3.79
28.13
22.64
13.63
10.01
53.94
12.71
8.11


24
97.4
200.1
66.3

1.52
1.55

3.45
69.24
2.40
30.45
1.12
1.88
3.66
28.36
22.64
13.78
10.27
54.21
12.25
7.67


24
96.7
199.2
67.4

1.48
1.52

3.25
69.03
2.51
30.48
1.10
2.08
4.00
29.07
23.10
13.81
10.13
55.40
11.45
8.34


a Please refer to "General Procedure" for details concerning the various measurement criteria.
b Statistical significance based on 12 pigs only under each level of feeding and each sex which were individually fed.
* Significantly different (P<.05)
** Significantly different (P<.01)
NS Not significant







Florida Agricultural Experiment Stations


age liver (P < .01). Chops from full-fed pigs were significantly
tenderer (P < .01).
Method of feeding effect.-Individually fed pigs required only
3.35 pounds feed per pound gain compared to 3.56 for group fed
pigs. Significant differences were not observed for any of the
carcass measurement criteria, except for the percent four
lean cuts. In this case pigs individually fed yielded a higher
percent four lean cuts (P < .05).
Sex effect.-It is generally accepted that gilts gain slower
but more efficiently and yield leaner carcasses than barrows. In
this experiment gilts gained slightly slower than barrows. Gilts
were more efficient in gains and produced leaner carcasses. The
most noticeable difference was in loin eye area. A significant
interaction between sex and feed level was observed for rate of
gain, indicating that gilts gained relatively faster on restricted
feeding, whereas barrows gained relatively faster on the full-
feeding program. Chops from barrows tended to show greater
tenderness but the differences were not statistically significant.

Experiment 5
A summary of the results for Experiment 5 is presented in
Table 9.
Breed composition effect.-The three-way crossbred pigs
generally outperformed the two-way crossbred pigs (Lot 2 vs.
Lot 1). They also yielded somewhat leaner carcasses. However,
the only statistically significant difference observed was backfat
thickness (P < .01).
Level of feeding effect.-For a direct comparison of level of
feeding it is necessary to compare Lot 3 with Lot 4. The full-fed
pigs (Lot 3) gained significantly faster (P < .01) and required
approximately 30 days less time to reach slaughter weight. Full-
fed pigs also converted feed more efficiently than the restricted
pigs (3.54 vs. 4.66). Full-fed pigs dressed significantly better
(P < .05) and yielded a higher percent liver (P < .01). Re-
stricted pigs yielded carcasses carrying significantly less backfat
and a higher percent four lean cuts (P < .01).
Starting weight effect.-For this comparison it is necessary
to consider only Lots 2, 4, and 5, which were restricted commenc-







Table 9.-Feedlot performance and carcass data as influenced by breed composition, level of feeding and starting weight
(Experiment 5).a

Lot Number 1 2 3 4 5 Statistical Significance
Feed Level Restricted Restricted Full Restricted Restricted
Breed Composition b 2x 3x 3x 3x 3x Breed Feed Starting
Starting Weight 100 100 120 120 150 Composition Level Weight
Number of Barrows 5 5 6 6 6 Lot 1 vs Lot 3 vs Lot 4 vs
Number of Gilts 7 7 6 6 6 Lot 2 Lot 4 Lot 5

Number of animals 12 12 12 12 12 -
Initial wt., lb. 98.5 98.3 119.8 120.2 152.8 -
Slaughter wt., lb. 198.7 201.6 201.1 199.7 199.3 -
Number days on feed 84.9 82.6 42.1 71.6 40.1 -
Daily gain, lb.
First 4 weeks 1.07 1.22 1.95 1.19 NS ** NS
Entire period 1.18 1.25 1.93 1.11 1.16 NS ** NS
Daily feed intake, lb. 5.11 4.95 6.83 5.17 5.15 -
Feed/lb. gain, lb. 4.33 3.96 3.54 4.66 4.44
Dressing percent 67.83 67.72 70.21 69.13 69.22 NS NS
Percent liver 2.30 2.27 2.86 2.10 2.18 NS ** NS
Carcass length, in. 30.98 30.67 30.13 30.68 30.39 NS NS NS
Carcass firmness score 2.42 2.83 2.08 2.58 2.42 NS NS NS
Backfat thickness, in. 1.18 1.10 1.30 1.17 1.12 ** ** NS
Loin eye area, sq. in. 3.75 3.99 4.03 4.30 3.90 NS NS **
Wt. of hams, lb. 27.21 27.80 27.28 28.04 27.92 -
Wt. of loins, lb. 21.84 22.71 22.69 23.00 22.48 -
Wt. of picnics, lb. 13.36 13.73 13.81 14.18 13.73 -
Wt. of butts, lb. 9.32 9.81 9.88 10.13 9.75 -
Percent 4 lean cuts 53.31 54.31 51.83 54.64 53.55 NS ** NS
Marbling score 8.25 9.04 10.67 9.50 9.54 NS NS NS

a Please refer to "General Procedure" for details concerning the various measurement criteria.
b 2X Duroc x Landrace; 3X (Duroc x Landrace) x Hampshire.
* Significantly different (P<.05)
** Significantly different (P<.01)
NS Not significant







Florida Agricultural Experiment Stations


ing at respective weights of 100, 120, and 150 pounds. Differ-
ences in performance and carcass characteristics were generally
not significant. Pigs in Lot 4 (120 pounds initial weight) yielded
somewhat leaner carcassas as indicated by a higher percent
four lean cuts and considerably greater loin eye area (P < .01).
When compared to the full-fed group (Lot 3) all restricted lots,
irrespective of initial weights, yielded leaner carcasses. The
data suggest that 50 pounds of weight gain under a restricted
feed intake was adequate to improve carcass leanness signifi-
cantly.
Sex effect.-Data on the influence of sex, which are not pre-
sented in the table, indicated that gilts gained slightly faster
(1.41 vs. 1.38) and more efficiently (4.13 vs. 4.29) than barrows.
Percent four lean cuts and loin eye area were 53.82 and 4.26 for
the gilts, and 52.86 and 3.89 for the barrows.

Experiments 6 and 7
Summaries of the results for Experiments 6 and 7 are pre-
sented in Tables 10 and 11, respectively. Combined results of
the two experiments for the main treatment variables are pre-
sented in Table 12.
The feeding treatments for Experiments 6 and 7 were
identical, and the two experiments were conducted nearly con-
currently, thus imposing approximately the same weather condi-
tions. However, Experiment 6 was conducted on concrete in
close confinement, and the pigs were all individually fed. Experi-
ment 7 was conducted in small pasture lots, and the pigs were
group-fed. The feedlot performance of the pigs in Experiment
6 was much superior to that of the pigs in Experiment 7. This
marked difference in gains (1.35, 1.22, 2.07, and 1.85 vs. 1.32,
1.06, 1.69, and 1.47) for the respective lots is of interest. Simi-
larly, the feed required per pound gain was greatly different
(3.70, 4.09, 3.44, and 3.78 vs. 3.73, 4.63, 3.67, and 3.77). Since
pigs used in both experiments were of similar breeding and
quality, it appears that the method of feeding or environmental
factors or both have influenced results. In a previous experiment
(Experiment 4) it was observed that rate of gain was not affect-
ed by method of feeding (individual vs. group) but that feeding
efficiency was much better for individually fed pigs. It is
probable that cold and wet weather conditions during the experi-








Feed Restriction of Swine


Table 10.-The relationship of feed restriction and dietary protein level
(Experiment 6) .a
Group 1 2 3 4
Feed Level Restricted Restricted Full Full
Percent Protein 17 11 17 11
Number of pigs 10 10 10 10
Initial wt., lb. 111.6 111.4 111.8 112.4
Slaughter wt., lb. 196.7 198.2 200.0 201.5
Number days on feed 63.0 71.1 42.3 48.2
Daily gain, lb. 1.35 1.22 2.07 1.85
Daily feed intake, lb. 5.00 4.99 7.12 6.99
Feed per lb. gain, lb. 3.70 4.09 3.44 3.78
Dressing percent 71.43 70.75 71.26 71.50
Carcass length, in. 30.00 30.33 29.41 30.45
Backfat thickness, in. 1.20 1.24 1.37 1.41
Loin eye area, sq. in. 4.30 3.86 3.95 3.50
Wt. of hams, lb. 28.83 27.94 27.17 26.93
Wt. of loins, lb. 21.61 20.67 20.70 20.43
Wt. of picnics, lb. 13.44 13.72 13.31 12.80
Wt. of butts, lb. 9.47 9.08 9.26 8.98
Percent 4 lean cuts 52.19 50.92 49.52 48.01
Marbling score 5.85 10.20 8.40 14.95
Tenderness of fry chops
Panel 6.10 6.10 6.63 6.43
Shear 8.33 7.80 8.08 7.48
a Please refer to "General Procedure" for details concerning the various measurements
criteria.


mental period also contributed to the differences in performance.
Pigs fed in Experiment 7 were sheltered only by trees. Earlier
experiments (2 and 3) have also suggested that close confine-
ment may favor better performance under restricted feeding.
In contrast to feedlot performance, carcass measurements
generally favored pigs from Experiment 7. This was more
marked in the case of the full-fed pigs, and probably reflected
in part the slower rate of gain made by the full-fed pigs in the
pasture lots.

Level of feeding effect.-As shown in Table 12, full-fed pigs
gained significantly faster and more efficiently than restricted
pigs (P < .01). Carcasses of the restricted pigs had less backfat,
had larger loin eyes, and yielded a higher percent four lean
cuts (P < .01). Marbling was greater in the loin eye muscle
of the full-fed pigs, but the difference was not statistically signi-
ficant. Tenderness measurements showed that pork chops from








Florida Agricultural Experiment Stations


Table 11.-The relationship of feed restriction and dietary protein level
(Experiment 7).a

Lot 1 2 3 4
Feed Level Restricted Restricted Full Full
Percent Protein 17 11 17 11

Number of pigs 10 10 10 10
Initial wt., lb. 109.1 109.4 109.2 109.3
Slaughter wt., lb. 202.6 201.3 203.4 199.9
Number days on feed 70.8 86.7 55.7 61.6
Daily gain, lb. 1.32 1.06 1.69 1.47
Daily feed intake, lb. 4.92 4.91 6.20 5.54
Feed per lb. gain, lb. 3.73 4.63 3.67 3.77
Dressing percent 67.62 67.50 70.79 69.58
Carcass length, in. 30.05 30.35 30.20 29.94
Backfat thickness, in. 1.13 1.18 1.30 1.27
Loin eye area, sq. in. 4.23 3.60 4.13 3.66
Wt. of hams, lb. 28.22 27.09 28.84 26.60
Wt. of loins, lb. 21.68 20.43 22.26 20.48
Wt. of picnics, lb. 13.10 12.77 13.05 12.87
Wt. of butts, lb. 9.67 9.40 9.98 9.44
Percent 4 lean cuts 53.05 51.11 51.67 49.90
Marbling score 6.75 14.35 6.70 10.61
Tenderness of fry chops
Panel 5.78 5.90 6.30 5.75
Shear 9.44 9.33 8.15 9.55
a Please refer to "General Procedure" for details concerning the various measurement
criteria.


the full-fed pigs were slightly more tender, but these differences
were not statistically significant. However, the trend was in
the same direction as observed in Experiments 2, 3, and 4.

Protein level effect.-Pigs fed a 17 percent protein diet gained
faster and more efficiently (P < .01) than pigs fed 11 percent
protein. Pigs fed the higher level of protein also yielded leaner
carcasses as measured by loin eye area (P < .01), percent four
lean cuts (P < .01), and marbling scores (P < .01). It is very
evident from these two experiments that protein level in the
diet is a critical aspect of restricted feeding. Commonly recom-
mended levels for finishing hogs on full-feed may be inadequate
under limited feeding, especially for good meat-type hogs.
Dietary protein level did not appear to exert much influence on
pork chop tenderness measurements.
The influence of dietary protein level and level of feeding on
pork chops is shown pictorially in Figure 3.







Table 12.-Feedlot performance and carcass data as influenced by main treatment variables (Experiments 6 and 7 combined). a

Feed Level Protein Level % Statistical Significance
Comparison Restricted Full 17 11 Feed Level Protein Level


Number of pigs
Initial wt., lb.
Slaughter wt., lb.
Number days on feed
Daily gain, lb.
Daily feed intake, lb.
Feed per lb. gain, lb. b
Dressing percent
Carcass length
Backfat thickness, in.
Loin eye area, sq. in.
Wt. of hams, lb.
Wt. of loins, lb.
Wt. of picnics, lb.
Wt. of butts, lb.
Percent 4 lean cuts
Marbling score
Tenderness of chops
Panel
Shear


40
110.4
199.7
72.0
1.24
4.96
4.04
69.33
30.18
1.19
4.00
28.02
21.10
13.26
9.41
51.82
9.29


40
110.7
201.2
51.1
1.77
6.46
3.67
70.78
30.00
1.34
3.81
27.39
20.97
13.01
9.42
49.76
10.17


40
110.4
200.7
56.1
1.61
5.81
3.64
70.28
29.92
1.25
4.15
28.27
21.56
13.23
9.60
51.61
6.93


40
110.6
200.2
64.0
1.40
5.61
4.07
69.83
30.27
1.28
3.66
27.14
20.50
13.04
9.23
49.99
12.53


NS NS
NS NS


a Please refer to "General Procedure" for details concerning the various measurement criteria.
b Statistical significance based on Experiment 6 only, in which pigs were individually fed.
** Significantly different (P < .01)
NS Not significant






Florida Agricultural Experiment Stations


17 F


17 L A I


Figure 3.-The four chops shown above depict the average lain eye size and
degree of marbling for the four treatment groups studied in Experiments 6 and 7.
These values are shown below.
Chop Loin Eye Marbling
Designation Feeding Treatment Area, Sq. In. Score
11 L 11% protein, restricted 3.37 12.27
11 F 11% protein, full-fed 3.58 12.78
17 L 17% protein, restricted 4.27 6.30
17 F 17% protein, full-fed 4.04 7.52







Feed Restriction of Swine


SUMMARY
Seven feeding and slaughter experiments, involving a total of
348 pigs, were conducted to study the feasibility of restricting
the feed intake of swine during the finishing period. The experi-
ments were conducted during the period from September 1962
to June 1964.
The feeding experiments were initiated when the pigs
weighed approximately 100 to 110 pounds and terminated at a
slaughter weight of approximately 200 pounds. An exception
was the case of Experiment 5 in which initial weights for the
various lots were 100, 120, and 150 pounds. These initial weights
were a part of experimental design.
The diets consisted of fortified corn-soybean meal mixtures.
The control pigs or full-fed pigs were fed by self-feeder. Animals
on the restricted regime were fed the same dry-meal mixtures at
a continuous level of 5 pounds per head per day in troughs.
Carcass cut-out data were obtained on all animals and tender-
ness determinations were made on chops from all animals except
those from Experiment 5.
Table 13 summarizes the combined data for the several ex-
periments. Pigs restricted to 5 pounds of feed per head daily
required an average of 17.8 more days to reach slaughter weight.
Their gains were 1.32 pounds per day compared to 1.82 for the
full-fed pigs. Restricted pigs required 3.85 pounds of feed for
each pound of gain, while full-fed pigs required only 3.55 pounds
of feed. This represents an increase of 8.5 percent in feed re-
quirement as a result of restricting feed intake. It was observed
that restricted-fed pigs under close confinement were generally
more efficient in feed conversion than restricted-fed pigs given
generous space for ranging.
Dressing percent favored full-fed pigs by a small margin, but
this was not a consistent observation among the experiments.
All measurements indicative of superior carcass leanness
clearly favored the restricted pigs (Table 13). Carcasses from
restricted pigs were consistently slightly longer, averaging 0.2
inch longer. Although all pigs were quite lean in terms of backfat
thickness measurements, the restricted pigs averaged 0.14 inch
less. This was a very consistent and highly significant difference
in all experiments. Full-fed pigs yielded loins with an eye mea-
surement of only 3.76 square inches compared to 3.92 for re-








Florida Agricultural Experiment Stations


Table 13.-Summary of results. (Data from 7 experiments combined)

Feeding Level Restricted Full

Number of pigs a 156 156
Number days on feed 71.3 53.5
Av. initial wt., lb. 104.0 103.8
Av. final wt., lb. 198.2 201.2
Av. daily gain, lb. 1.32 1.82
Fed per lb. gain, lb. 3.85 3.55
Dressing percent 69.68 70.45
Carcass length, in. 30.13 29.93
Backfat thickness, in. 1.12 1.26
Carcass firmness score b 2.40 1.99
Loin eye area, sq. in. 3.92 3.76
Percent 4 lean cuts 53.74 51.66
Marbling score of loin eye 10.11 11.64
Chop tenderness (panel)c 5.84 6.08
Chop tenderness (shear) 8.36 7.73
a A total of 36 pigs fed in Experiment 5 were not included in this summary because of
experimental design preclusion.
b The carcass firmness scores shown here were based on only 116 pigs from each feeding
level. Data were not available for Experiments 6 and 7.
c Chop tenderness scores registered by the taste panel were based on 120 pigs for each
feeding level. Data were not available for the pigs fed in Experiments 4 and 5.


stricted pigs. Percent four lean cuts were 53.74 and 51.66,
respectively, for restricted and full-fed pigs. This represents a
marked improvement in lean tissue production and was a con-
sistent observation.
Full-fed pigs tended to exhibit more intramuscular fat de-
position as indicated by the visual marbling scores on the cross
section of the loin eye muscle. These differences were small,
fairly consistent, but not statistically significant in any of the
experiments. Tenderness determinations made on the cooked
pork chops indicated that the restricted pigs were generally
slightly less tender than full-fed pigs. Results obtained by both
a four-member trained panel and the Warner-Bratzler shear
method indicated this difference. Differences measured were
statistically significant in two of the experiments.
Although not shown in Table 13, data were collected on the
comparable performance of gilts and barrows in Experiments
1 through 4. Daily gains were approximately the same, favoring
barrows only slightly. However, gilts were much more efficient
in the conversion of feed to body gain. Gilts yielded longer car-







Feed Restriction of Swine


cases, with less backfat, larger loin eye areas, and a considerably
greater percent four lean cuts. Marbling scores indicated
greater fat infiltration of the loin eye muscle for the barrows.
Important differences in chop tenderness due to sex were not
apparent.
The importance of adequate dietary protein was demonstrated
under both full-feeding and limited feeding regimes (Experi-
ments 6 and 7). Pigs fed a 17 percent protein diet gained much
faster and more efficiently and yielded leaner carcasses than pigs
fed an 11 percent protein diet.


CONCLUSIONS AND RECOMMENDATIONS
The practice of restricting the feed intake of swine during
the finishing period did not prove advantageous under the condi-
tions of this study. The increased time required to finish the
hogs and the greater amount of feed required per unit of gain
were major adverse factors. A marked improvement in percent
lean cuts was observed due to feed restriction. This, however,
was not reflected in a greater monetary return. All animals,
full-fed and restricted, were graded on foot as No. 1 market
hogs. Under our present hog-marketing system the two groups
returned the same amount of money per hundredweight. If the
animals had been sold on the rail according to percent lean-cut
yield, restricted pigs would have returned more money than
the full-fed pigs. Since there is not presently a standard pro-
cedure established as to increment value of percent lean cuts
it is impossible to state whether the practice of feed restriction
as employed in this study would have been economically feasible
under the rail-grading method of sale.
It is quite obvious that restricted feeding of finishing hogs
is only a temporary measure for the improvement of carcass
quality. Lasting improvement must come through genetic selec-
tion and nutritional research. For this reason it is recommended
that producers place first emphasis on the production of lean,
heavily muscled strains of hogs using full-feeding regimes.
Some producers have adopted automated restricted feeding
programs and are satisfied with this method of feeding. If such
a program is followed it is recommended that the animals not
be restricted until a liveweight of 100 to 125 lb. is reached and
that they be held in close confinement during the period of re-







Florida Agricultural Experiment Stations


striction. The feeding level should range from 75 to 90 percent
of a full-feed intake with the greater restriction occurring dur-
ing the final stages of the feeding period. Pigs should be care-
fully grouped according to size, since competition for feed be-
comes intense, which tends to result in less uniformity in animal
performance. The dietary protein level is somewhat more critical
under restricted feeding and should be given careful considera-
tion. Producers using restricted feeding programs should ar-
range to sell hogs by means of on-the-rail grading so as to realize
full value for their product.


ACKNOWLEDGMENTS
To W. E. Collins, L. S. Taylor and B. R. Cannon, Swine Herds-
men; Jeff Jeter, Meats Laboratory Manager; N. H. Anh,
Graduate Assistant; and Mrs. Barbara Sullivan and Richard
Newman, Laboratory Assistants, the authors extend their grate-
ful appreciation for many hours of devoted assistance on this
project. To the several other persons, graduate students and
staff, who gave generously of their time to assist with various
phases of the study the authors are deeply appreciative.
The authors are also indebted to the following commercial
companies for supplies and grant-in-aid support: American
Cyanamid Co., Princeton, New Jersey; Chas. Pfizer & Co., Inc.,
Terre Haute, Indiana; Eli Lilly and Co., Greenfield, Indiana; and
Merck & Co., Rahway, New Jersey.








Feed Restriction of Swine


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Florida Agricultural Experiment Stations


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