Feeding interval effects on growth, puberty, and pregnancy rates in yearling Bos indicus and Bos taurus beef heifers

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Title:
Feeding interval effects on growth, puberty, and pregnancy rates in yearling Bos indicus and Bos taurus beef heifers
Series Title:
2009 Florida Beef Report
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Book
Creator:
Austin, Brad
Hersom, Matt
Yelich, Joel
Publisher:
Institute of Food and Agricultural Sciences, University of Florida
Place of Publication:
Gainesville, Fla.
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University of Florida
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Feeding Interval Effects on Growth, Puberty, and Pregnancy Rates in
Yearling Bos indicus and Bos taurus Beef Heifers

Brad Austin1
Matt Hersom
Joel Yelich



Supplementation of developing heifers with distillers grains three days/week has no negative effects on
heifer growth or reproductive performance compared to daily supplementation.


Summary
The objective of this study was to examine the
effects of daily versus three d/wk
supplementation on growth, age at puberty,
estrous synchronization response, and
pregnancy rates of yearling Brangus and Angus
heifers consuming round bale silage (RBS).
Sixty heifers (30, Angus; 30, Brangus) were
stratified by initial body weight, breed, and age
and randomly allocated to 12 pens. Pens were
randomly assigned to one of two treatments: 1)
distillers grains and soybean meal supplemented
daily; or 2) distillers grains and soy bean meal
supplemented three d/wk. Supplement
consumption and RBS offered were similar for
both treatments. Heifers supplemented daily
had similar ADG as compared to heifers
supplemented three d/wk (1.82 vs. 1.79 lb/d).
The number of heifers reaching puberty by
breeding tended to be greater for daily fed
heifers. Synchronized pregnancy rates and total
28 day Al pregnancy rates were also similar for
both treatments. In this study, three d/wk
supplementation of developing heifers had no
effect on heifer growth rates or pregnancy rates
as compared to daily supplementation.

Introduction
The development of heifers is one of the major
economic considerations in a cow-calf
operation. Heifers that calve by two years of
age have greater lifetime productivity than
heifers that calve at an older age. Heifers must
be maintained on a high plane of nutrition to
reach puberty and conceive by 14 to 15 mo of


age. Most cattle raised in the Southeastern
United States have some degree of Bos indicus
breeding and heifers with Bos indicus breeding
tend to mature slower and reach puberty at older
ages than Bos taurus heifers. The influence of
Bos indicus breeding can negatively affect the
rancher's success of having heifers pregnant to
calve at two yr of age. The impact of
supplemental nutrition is increasingly important
in these situations.

Supplementation of heifers is a very common
practice, but producers are often concerned
about the labor inputs involved with
supplementation. Labor saving methods utilized
include: supplement type (liquid and self-
limiting), feeding method (hand fed, self fed),
and feeding intervals (daily, three times a week,
once a week). Little data is available on the
effects of supplementing heifers at different
intervals on growth and reproductive
performance. A better understanding of the
biological effects of these labor saving
supplementation methods can lead to more
efficient development of heifers.

The objective of this study was to examine the
effects of daily versus three d/wk
supplementation on age at puberty, estrous
synchronization response, and pregnancy rates
of yearling Brangus and Angus heifers
consuming RBS.


2009 Florida BeefReport










Procedure
This study was conducted at the Santa Fe Beef
Unit, located near Gainesville in northern
Alachua County. Sixty heifers (n=60) were
stratified by age, body weight, and sire into 12
pens (6 pens Angus and 6 pens Brangus).
Beginning in October 2006, heifers were
supplied ad libitum access to bermudagrass
round bale silage (RBS; 51% dry matter, 12.9%
crude protein, 53.9 % total digestible nutrients)
and free choice mineral. Heifers were
supplemented with distillers dried grains (DDG)
and soybean meal to gain approximately 1.5
lb/d, with half of the pens supplemented daily
(CON) and the remaining pens supplemented
three d/wk (3X). Soybean meal was fed to help
meet degradable intake protein requirements as
determined by the NRC computer model.
Heifers were weighed and bled weekly to
determine average daily gain (ADG) and age at
puberty. Body condition scores (BCS) and hip
heights (HH) were taken monthly. A shrunk
body weight (following a 12-h shrink) was
collected at the beginning and the end of the
trial.

Heifers were synchronized for artificial
insemination on d 145 of the experiment. A
CIDR was inserted concurrent with GnRH.
Seven d later the CIDR was removed and
prostaglandin was administered to synchronize
estrus. Estrus was detected for 72 h, using the
Heatwatch system, and heifers were inseminated
approximately 8-12 h after the onset of estrus by
a single AI technician. Heifers not exhibiting
estrus by 72 h after prostaglandin received
GnRH and fixed-time AI. Detection of estrus
and AI were continued for 27 d while heifers
remained in their respective pens and continued
to receive supplement treatments. Pregnancy
was diagnosed by ultrasonography 31 d after
prostaglandin at which time heifers were
removed from supplementation treatments and
pens.

Data for ADG, HH, and BCS were analyzed
using the PROC MIXED procedure of SAS.
The model statement contained the effects of
treatment, breed, and the interaction. Pen within
treatment was the random effect. Pregnancy and
puberty data were analyzed using PROC GLM.


Least square means were determined and
differences between means were considered
significant is P<0.05.

Results
The ADG of the heifers for the trial was greater
than predicted by the model, and ADG were
similar between treatments (P=0.83). Heifers
averaged 1.84 lb/d for the entire trial for both
treatments. Shrunk weight ADG for the trial
were also similar (P=0.72) between treatments
(CON- 1.82, 3X- 1.79 lb/d). The Angus and
Brangus heifers gains were similar (P=0.86)
regardless of treatment (Angus 1.91 vs. Brangus
1.77 lb/d). Total RBS offered was similar
(P=0.73) between treatments (CON= 17,787 lbs;
3X= 17,556 lbs), and DDG consumption was
also similar (P=0.56) between treatments
(CON=2,891; 3X=2,970 lbs). Changes in hip
height were also similar between treatments
(P=0.95; 3.7 in for CON and 3X). Heifer gains
were not impaired by supplementing three d/wk
compared to daily supplementation. This
supports previous research conducted in cows
that three d/wk supplementation of protein feed
does not significantly affect cow performance
and therefore it can be used as means to save
labor in a feeding program.

Heifers in the CON treatment tended (P=0.09) to
have a greater percentage pubertal (60%) at
breeding compared to 3X heifers (40%, Table
1). It is unclear at this point if this difference is
due to the feeding regiment used (daily vs. three
d/wk) or it is just due to the limited number of
heifers in that group. Estrus response tended
(P=0.10) to be greater for CON (77%) compared
to 3X (57%). The synchronized pregnancy rates
were similar (P=0.30) for 3X (57%) compared
to CON (43%). Total 28 d AI pregnancy rates
were also similar (P=0.59) between treatments
(CON=63%; 3X=70%). Synchronized
pregnancy rates for the heifers exceeded
previous reproductive performance for heifers at
the Santa Fe beef unit. It is important to note
that even though only 50% of the heifers had
reached puberty by the start of the breeding
season, the synchronization treatment still
resulted in a first service AI pregnancy rate of
50%. This indicates the importance of using a


2009 Florida BeefReport









synchronization treatment that utilizes a
progestagen source in inducing puberty in the
non-pubertal heifers.

In conclusion, DDG showed no negative effects
on the development of yearling Angus and
Brangus heifers in combination with RBS.
Heifers adapted easily to DDG and RBS, and
exceeded the computer modeled performance
during the study. Three-time a week feeding of
developing heifers offers a management practice
that may help significantly reduce labor cost
without sacrificing heifer growth rates or
pregnancy rates.


Table 1. Summary of reproductive performance of heifers supplemented Daily or 3X a week
Daily 3X P-value
Pubertal at AI (%) 18/30 (60) 12/30 (40) 0.09
Estrous response (%)a 23/30 (77) 17/30 (57) 0.10
Synchronized pregnancy rate (%)b 13/30 (43) 17/30 (57) 0.30
30 d AI pregnancy rate (%)c 19/30 (63) 21/30 (70) 0.59
a Percentage of heifers displaying estrus during the 3 d after PGF2 of the total treated.
b Percentage of heifers pregnant during the synchronized breeding of the total treated
c Percentage of heifers pregnant to AI during the dirst 30 d of the breeding season of the total number
of heifers.

















'Brad Austin, Gradute Student; Matt Hersom, Assistant Professor; Joel Yelich, Associate
Professor, UF-IFAS Animal Sciences, Gainesville, FL


2009 Florida BeefReport












































































106 2009 Florida BeefReport




Full Text

PAGE 1

Feeding Interval Effects on Growth, Puberty, and Pregnancy Rates in Yearling Bos indicus a nd Bos taurus Beef Heifers Brad Austin 1 Matt Hersom Joel Yelich Summary The objective of this study was to examine the effects of daily versus three d/wk supplementation on growth, age at puberty, estrous synchronization response, and pregnancy rates of yearling Brangus and Angus heifers consuming round bale silage (RBS). Sixty heifers (30, Angus; 30, Brangus) were stratified by initial body weight, breed, and age and randomly allocated to 12 pens. Pens were randomly assigned to one of two treatments: 1) distillers grains and soybean meal supplemented daily; or 2) distillers grains and soy bean meal supplemented three d/wk. Supplement consumption and RBS offered were similar for both treatments. Heifers supplemented daily had similar ADG as compared to heifers supplemented three d/wk (1.82 vs. 1.79 lb/d). The number of heifers reaching puberty by breeding tended to be greater for daily fed heifers. Synchronized pregnancy rates and total 28 day AI pregnancy rates were also similar for both treatments. In this study, three d/wk supplementation of developing heifers had no effect on heifer growth rates or pregnancy rates as compared to daily supplementation. Introduction The development of heifers is one of the major economic considerations in a cow-calf operation. Heifers that calve by two years of age have greater lifetime productivity than heifers that calve at an older age. Heifers must be maintained on a high plane of nutrition to reach puberty and conceive by 14 to 15 mo of age. Most cattle raised in the Southeastern Un ited States have some degree of Bos indicus breeding and heifers with Bos indicus breeding tend to mature slower and reach puberty at older ages than Bos taurus heifers. The influence of Bos indicus breeding can negatively affect the having heifers pregnant to calve at two yr of age. The impact of supplemental nutrition is increasingly important in these situations. Supplementation of heifers is a very common practice, but producers are often concerned about the labor inputs involved with supplementation. Labor saving methods utilized include: supplement type (liquid and selflimiting), feeding method (hand fed, self fed), and feeding intervals (daily, three times a week, once a week). Little data is available on the effects of supplementing heifers at different intervals on growth and reproductive performance. A better understanding of the biological effects of these labor saving supplementation methods can lead to more efficient development of heifers. The objective of this study was to examine the effects of daily versus three d/wk supplementation on age at puberty, estrous synchronization response, and pregnancy rates of yearling Brangus and Angus heifers consuming RBS. Supplementation of developing heifers with distillers grains three days/week has no negative effects on heifer growth or reproductive performance compared to daily supplementation.

PAGE 2

Procedure This study was conducted at the Santa Fe Beef Unit, located near Gainesville in northern Alachua County. Sixty heifers (n=60) were stratified by age, body weight, and sire into 12 pens (6 pens Angus and 6 pens Brangus). Beginning in October 2006, heifers were supplied ad libitum access to bermudagrass round bale silage (RBS; 51% dry matter, 12.9% crude protein, 53.9 % total digestible nutrients) and free choice mineral. Heifers were supplemented with distillers dried grains (DDG) and soybean meal to gain approximately 1.5 lb/d, with half of the pens supplemented daily (CON) and the remaining pens supplemented three d/wk (3X). Soybean meal was fed to help meet degradable intake protein requirements as determined by the NRC computer model. Heifers were weighed and bled weekly to determine average daily gain (ADG) and age at puberty. Body condition scores (BCS) and hip heights (HH) were taken monthly. A shrunk body weight (following a 12-h shrink) was collected at the beginning and the end of the trial. Heifers were synchronized for artificial in semination on d 145 of the experiment. A CIDR was inserted concurrent with GnRH. Seven d later the CIDR was removed and prostaglandin was administered to synchronize estrus. Estrus was detected for 72 h, using the Heatwatch system, and heifers were inseminated approximately 8-12 h after the onset of estrus by a single AI technician. Heifers not exhibiting estrus by 72 h after prostaglandin received GnRH and fixed-time AI. Detection of estrus and AI were continued for 27 d while heifers remained in their respective pens and continued to receive supplement treatments. Pregnancy was diagnosed by ultrasonography 31 d after prostaglandin at which time heifers were removed from supplementation treatments and pens. Data for ADG, HH, and BCS were analyzed using the PROC MIXED procedure of SAS. The model statement contained the effects of treatment, breed, and the interaction. Pen within treatment was the random effect. Pregnancy and puberty data were analyzed using PROC GLM. Least square means were determined and differences between means were considered significant is P<0.05. Results The ADG of the heifers for the trial was greater than predicted by the model, and ADG were similar between treatments ( P=0.83). Heifers averaged 1.84 lb/d for the entire trial for both treatments. Shrunk weight ADG for the trial were also similar ( P =0.72) between treatments (CON1.82, 3X1.79 lb/d). The Angus and Brangus heifers gains were similar ( P =0.86) regardless of treatment (Angus 1.91 vs. Brangus 1.77 lb/d). Total RBS offered was similar ( P=0.73) between treatments (CON= 17,787 lbs; 3X= 17,556 lbs), and DDG consumption was also similar ( P =0.56) between treatments (CON=2,891; 3X=2,970 lbs). Changes in hip height were also similar between treatments ( P=0.95; 3.7 in for CON and 3X). Heifer gains were not impaired by supplementing three d/wk compared to daily supplementation. This supports previous research conducted in cows that three d/wk supplementation of protein feed does not significantly affect cow performance and therefore it can be used as means to save labor in a feeding program. Heifers in the CON treatment tended ( P =0.09) to have a greater percentage pubertal (60%) at breeding compared to 3X heifers (40%, Table 1). It is unclear at this point if this difference is due to the feeding regiment used (daily vs. three d/wk) or it is just due to the limited number of heifers in that group. Estrus response tended ( P=0.10) to be greater for CON (77%) compared to 3X (57%). The synchronized pregnancy rates were similar ( P =0.30) for 3X (57%) compared to CON (43%). Total 28 d AI pregnancy rates were also similar ( P =0.59) between treatments (CON=63%; 3X=70%). Synchronized pregnancy rates for the heifers exceeded previous reproductive performance for heifers at the Santa Fe beef unit. It is important to note that even though only 50% of the heifers had reached puberty by the start of the breeding season, the synchronization treatment still resulted in a first service AI pregnancy rate of 50%. This indicates the importance of using a

PAGE 3

synchronization treatment that utilizes a progestagen source in inducing puberty in the non-pubertal heifers. In conclusion, DDG showed no negative effects on the development of yearling Angus and Brangus heifers in combination with RBS. Heifers adapted easily to DDG and RBS, and exceeded the computer modeled performance during the study. Three-time a week feeding of developing heifers offers a management practice that may help significantly reduce labor cost without sacrificing heifer growth rates or pregnancy rates. Table 1. Summary of reproductive performance of heifers supplemented Daily or 3X a week Daily 3X P value Pubertal at AI (%) 18/30 (60) 12/30 (40) 0.09 Estrous response (%) a 23/30 (77) 17/30 (57) 0.10 Synchronized pregnancy rate (%) b 13/30 (43) 17/30 (57) 0.30 30 d AI pregnancy rate (%) c 19/30 (63) 21/30 (70) 0.59 a Percentage of heifers displaying estrus during the 3 d after PGF2 of the total treated. b Percentage of heifers pregnant during the synchronized breeding of the total treated c Percentage of heifers pregnant to AI during the dirst 30 d of the breeding season of the total number of heifers. 1 Brad Austin, Gradute Student; Matt Hersom Assistant Professor; Joel Yelich, Associate Professor, UF IFAS Animal Sciences, Gainesville, FL