Evaluation of beef cow and calf separation systems to improve reproductive performance of first-calf cows

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Evaluation of beef cow and calf separation systems to improve reproductive performance of first-calf cows
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Martins, Paulo, G.M.A.
Arthington, John D.
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Institute of Food and Agricultural Sciences, University of Florida
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Gainesville, Fla.
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Evaluation of Beef Cow and Calf Separation Systems to Improve
Reproductive Performance of First-Calf Cows

Paulo G. M. A. Martins, John D. Arthington1

Repeated 48-h calf withdrawal may be an effective option for the reproductive management of first-
calf Brahman crossbred cows.


Summary
The objectives were to compare the effects of a
traditional 48-h calf withdrawal to early-
weaning and repeated 48-h calf withdrawals on
postpartum interval and measures of
performance of first-calf cows. Over two
consecutive years, a total of 112 primiparous,
Brahman x British crossbred cow-calf pairs
were randomly allotted to three treatments: EW
(early weaned); IW (interval weaned 48-h calf
withdrawal; four times, 20 d apart); and CON
(control; single 48-h calf withdrawal).
Treatments were initiated at the start of a 90-d
breeding season (average days postpartum =97
19). Blood samples were collected over 90 d
at 10 d intervals for determination of
concentrations of progesterone. Cow BW was
measured at the start (d 0), middle (d 41), and
end (d 90) of the study, and calf BW was
determined at the start and end of the study.
Pregnancy was diagnosed by transrectal
ultrasonography at approximately 45 d after the
end of the breeding season. By d 30 of the
breeding season, there were more EW cows
cycling than IW and CON cows (89.5, 68.9, and
61.1 %, respectively; P = 0.03). Cow and calf
BW did not differ at the beginning of the
breeding season, but was greater (P < 0.01) for
EWvs. IW and CON cows and calves at the end
of the study (d 90; 850, 793, and 795, and 377,
278, and 292 lb for EW, IW, and CON cows and
calves, respectively; SEM =8.1 and 4.7). Early-
weaned cows tended (P = 0.06) to have a
greater pregnancy rate compared to IW and
CON cows and IW cows had a greater (P
0.03) pregnancy rate than CON cows (94.4,


89.7 and 71.7% pregnant for EW, IW, and CON,
respectively). Compared to traditional, single-
time, 48-h calf withdrawal, repeated 48-h calf
withdrawal resulted in similar cow BWand BCS
changes, reduced calf BW gain, hastened
postpartum anestrus period, and greater
pregnancy rate.

Introduction
Percent calf crop is a leading variable impacting
the profit of a cow-calf operation. Therefore, to
produce a calf each year; cows must maintain a
postpartum anestrous period of approximately
80 d or less, which is known to be a major factor
impacting calf crop. Suckling, calf presence,
and cow body condition score (BCS) are all
factors known to impact the duration of
postpartum anestrous.

Early weaning (EW) can be a practical and
profitable management option for cow-calf
operations. Compared to traditional weaning
systems, EW cows have been shown to have
greater BCS and pregnancy rate with decreased
dry matter intake and days of postpartum
anestrus. However, there are some disadvantages
in adopting EW, such as greater labor and feed
requirements for the calves and the need to
identify cow/calf pairs. As an alternative to
permanently separating the cows and calves,
temporary calf withdrawal may be a low-cost
management practice for reducing postpartum
anestrous and inducing ovulation in suckling
beef cows, under grazing conditions.


'Range Cattle Research and Education Center, University of Florida, Ona, FL










The objective the current study was to compare
the effects of a traditional 48-h calf withdrawal
to early-weaning and repeated 48-h calf
w withdraw als on post-partum interval and
measures of performance of first-calf beef cows.

Materials and Methods
This study was conducted over two consecutive
years (beginning January 2009) at the University
of Florida, Range Cattle Research and Education
Center (RCREC). Fall-calving, 2-yr-old,
Brahman x British crossbred cow-calf pairs (n =
64 and 48 for Yr 1 and 2, respectively) were
randomly assigned to one of three treatments
consisting of early weaning (EW; calves early
weaned in January); interval weaning (IW; calf
withdrawal for 48 h, four times during the
breeding season, 20 d apart); and control (CON;
single 48-h calf withdrawal at the beginning of
breeding season). Treatments were initiated at
the start of the breeding season (95 + 20.7 d
postpartum). All cows were exposed to Angus
bulls (bull:cow ratio approximately 1:30) during
a 90-d breeding season (January to April). Cows
grazed bahiagrass (Paspalum notatum) pastures
and were provided free-choice access to
stargrass (Cynodon spp.) hay, as well as a
commercial mineral/vitamin mix and water.
Early-weaned calves were kept in dry lot pen for
10 d for acclimatization and then transferred to
annual ryegrass (Lolium multiflorum) pastures
and provided supplemental concentrate (16%
CP; 1.0% body weight daily). During the 48-h
withdrawal, IW and CON calves were kept
enclosed within a pen located inside the pasture.
Calves had tactile contact with their dam,
limited to head region, but they were not
allowed to suckle. Free-choice access to
concentrate and water was provided to the calves
during this 48-h period. At all other times, IW
and CON calves were allowed free access to
their dams.

Cow body weight (BW) was measured at the
start (d 0), middle (d 41), and end of the
breeding season (d 90). Calf BW was measured
at the start and end of the breeding season.


Pregnancy was diagnosed by transrectal
ultrasonography at approximately 45 d after the
end of the breeding season. To determine the
effects of treatment on the length of postpartum
anestrous, blood samples were collected on 10 d
intervals during the breeding season for analysis
of progesterone concentrations. Resumption of
cyclicity was defined as two consecutive
samples with concentrations of progesterone >
1.5 ng/mL.

Data were analyzed using the MIXED (BW,
BCS, postpartum interval) and GENMOD
(pregnancy rate) procedures of SAS. The model
statement contained the effects of treatment,
year, and treatment x year interaction. For
postpartum interval, the model statement also
included the effect of sampling time. For calf
BW, the model statement contained the effects
of treatment, sex, year and all possible
interactions. Since weaning treatment was
applied directly to the cow or calf, cow or calf
was the experimental unit for all analyses.
Treatment differences were compared by single
degrees of freedom contrasts, predefined as EW
vs. IW and CON, and IW vs. CON.
Significance was set at P < 0.05. Response
variables were BCS, BW, pregnancy rate and
initiation of estrous.

Results
There was no treatment x year interaction for
cow BW, and there was no treatment x sex x
year interaction for calf BW. Cow BW at the
beginning of the breeding season did not differ
(P > 0.10); however, at the end of the breeding
season (d 90), EW cows were heavier (P < 0.01)
than CON and IW cows (Table 1). Cow BCS
tended (P = 0.09) to be greater for EW cows
compared to CON and IW cows on d 90 (Table
1). Calf BW did not differ at the beginning of
the breeding season, but was greater (P < 0.01)
for EW vs. IW and CON calves on d 90 (Table
2). In addition, CON calves were heavier (P =
0.05) than IW calves on d 90 (Table 2). There
was no treatment x year interaction for
postpartum interval or cow pregnancy rate. By










d 30, more EW cows were cycling than IW and
CON (89.5, 68.9, and 61.1%, respectively; P =
0.02). On d 90, there was a tendency (P = 0.11)
for more IW cows to be cycling compared to
CON cows (94.6, 90.1, and 72.7 % cycling for
EW, IW, and CON cows, respectively). Overall
pregnancy rate tended (P = 0.06) to be greater
for EW vs. the average of IW and CON cows
(94.4 vs. 80.7%). Additionally, pregnancy rate
of IW cows was greater (P = 0.03) than CON
cows (90.1 vs. 72.7%).
In summary, compared to traditional, single-
time, 48-h calf withdrawal, repeated 48-h calf
withdrawal resulted in similar cow BW and BCS
changes, reduced calf BW gain, hastened
postpartum anestrus period, and greater
pregnancy rate. We conclude that repeated 48-h
calf withdrawal may be an effective option for
the management of first-calf, Brahman crossbred
cows, particularly for producers that are unable
or unwilling to early-wean (permanently
separate) cows and calves at the start of the
breeding season.


Acknowledgments
The authors thank Mr. Austin Bateman, Mr. Clay Newman and Ms. Andrea Dunlap for their technical
assistance during the conduct of this study, and fellowship from CAPES of Brazil to Paulo G.M.A.
Martins.










Table 1. Least squares means of cow body weights and BCS of control (CON), interval- (IW), and
early-weaning (EW) treatments'.
Contrasts
Interval- Early- SEM (CON&IW)
SEM CON vs. IW
Item Control weaned weaned vs. EW
Cow BW, lb
d 0 814 814 816 13.5 0.91 0.97
d 41 818 813 833 9.7 0.19 0.73
d 90 795 793 850 8.1 <0.01 0.80
BW gain, lb -25 -27 30 8.1 <0.01 0.80
Cow BCS2
d 0 4.3 4.6 4.5 0.16 0.28 0.20
d 90 3.9 4.0 4.7 0.23 0.09 0.85
Change -0.5 -0.4 +0.2 0.23 0.09 0.85
1EW = calves early-weaned on d 0; IW = 48-h calf withdrawal, 4 times during the breeding season, 20 d
apart; CON = single 48-h calf withdrawal on d 0. Treatments were initiated at the start of the breeding
season (d 0; 95 20.7 d postpartum).
2Cow body condition score was estimated using a nine-point scale where 1 = emaciated to 9 = obese.


Table 2. Effect of control (CON), interval- (IW) and early weaned (EW) on calf growth performance'.
Contrasts
Interval- Early- SEM (CON&IW)
SEM CON vs. IW
Item Control weaned weaned vs. EW
Calf BW, lb
dO 191 207 191 6.0 0.29 0.07
d 90 292 278 377 4.7 <0.01 0.05
BW gain, lb 91 77 176 4.7 <0.01 0.05
'EW = calves early-weaned on d 0; IW = 48-h calf withdrawal, 4 times during the breeding season, 20 d apart;
CON = single 48-h calf withdrawal on d 0. Treatments were initiated at the start of the breeding season (d 0;
95 20.7 d postpartum).




Full Text

PAGE 1

Evaluation of Beef Cow and Calf Separation Systems to Improve Reproductive Performance of First Calf Cows Paulo G. M. A. Martins John D. Arthington 1 Summary The objectives were to compare the effects of a traditional 48 h calf withdrawal to early weaning and repeated 48 h calf withdrawals on postpartum interval and measures of performance of first calf cows. Over two consecutive years, a total of 112 primiparo us, Brahman x British crossbred cow calf pairs were randomly allotted to three treatments: EW (early weaned); IW (interval weaned 48 h calf withdrawal; four times, 20 d apart); and CON (control; single 48 h calf withdrawal). Treatments were initiated at the start of a 90 d breeding season (average days postpartum = 97 19). Blood samples were collected over 90 d at 10 d intervals for determination of concentrations of progesterone. Cow BW was measured at the start (d 0), middle (d 41), and end (d 90) of the study, and calf BW was determined at the start and end of the study. Pregnancy was diagnosed by transrectal ultrasonography at approximately 45 d after the end of the breeding season. By d 30 of the breeding season, there were more EW cows cycling tha n IW and CON cows (89.5, 68.9, and 61.1 %, respectively; P = 0.03). Cow and calf BW did not differ at the beginning of the breeding season, but was greater (P < 0.01) for EW vs. IW and CON cows and calves at the end of the study (d 90; 850, 793, and 795, a nd 377, 278, and 292 lb for EW, IW, and CON cows and calves, respectively; SEM = 8.1 and 4.7). Early weaned cows tended (P = 0.06) to have a greater pregnancy rate compared to IW and CON cows and IW cows had a greater (P = 0.03) pregnancy rate than CON co ws (94.4, 89.7 and 71.7% pregnant for EW, IW, and CON, respectively). Compared to traditional, single time, 48 h calf withdrawal, repeated 48 h calf withdrawal resulted in similar cow BW and BCS changes, reduced calf BW gain, hastened postpartum anestr us period, and greater pregnancy rate. Introduction Percent calf crop is a leading variable impacting the profit of a cow calf operation. Therefore, to produce a calf each year; cows must maintain a postpartum anestrous period of approximately 80 d or les s, which is known to be a major factor impacting calf crop. Suckling, calf presence, and cow body condition score (BCS) are all factors known to impact the duration of postpartum anestrous. Early weaning (EW) can be a practical and profitable management option for cow calf operations. Compared to traditional weaning systems, EW cows have been shown to have greater BCS and pregnancy rate with decreased dry matter intake and days of postpartum anestrus. However, there are some disadvantages in adopting EW such as greater labor and feed requirements for the calves and the need to identify cow/calf pairs. As an alternative to permanently separating the cows and calves, temporary calf withdrawal may be a low cost management practice for reducing postpartum a nestrous and inducing ovulation in suckling beef cows, under grazing conditions. Repeated 48 h calf withdrawal may be an effective option for the reproductive management of first calf Brahman crossbred cows. 1 Range Cattle Research and Education Center, University of Florida, Ona, FL

PAGE 2

T he objective the current study was to compare the effects of a traditional 48 h calf withdrawal to early weaning and repeated 48 h calf withdrawals on post partum interval and measures of performance of first calf beef cows. Materials and Methods This study was conducted over two consecutive years (beginning January 2009) at the University of Florida, Range Cattle Research and Education Center (RCREC). Fall calving, 2 yr old Brahman x British crossbred cow calf pairs (n = 64 and 48 for Yr 1 and 2, respectively) were randomly assigned to one of three treatments consisting of early weaning ( EW ; calves early weaned in January); interval weaning ( IW ; calf withdrawal for 48 h, fo ur times during the breeding season, 20 d apart); and control ( CON ; single 48 h calf withdrawal at the beginning of breeding season). Treatments were initiated at the start of the breeding season (95 20.7 d postpartum). All cows were exposed to Angus bu lls (bull:cow ratio approximately 1:30) during a 90 d breeding season (January to April). Cows grazed bahiagrass ( Paspalum notatum ) pastures and were provided free choice access to stargrass ( Cynodon spp.) hay, as well as a commercial mineral/vitamin mix a nd water. Early weaned calves were kept in dry lot pen for 10 d for acclimatization and then transferred to annual ryegrass ( Lolium multiflorum ) pastures and provided supplemental concentrate (16% CP; 1.0% body weight daily). During the 48 h withdrawal, IW and CON calves were kept enclosed within a pen located inside the pasture. Calves had tactile contact with their dam, limited to head region, but they were not allowed to suckle. Free choice access to concentrate and water was provided to the calves dur ing this 48 h period. At all other times, IW and CON calves were allowed free access to their dams. Cow body weight (BW) was measured at the start (d 0), middle (d 41), and end of the breeding season (d 90). Calf BW was measured at the start and end of the breeding season. Pregnancy was diagnosed by transrectal ultrasonography at approximately 45 d after the end of the breeding season. To determine the effects of treatment on the length of postpartum anestrous, blood samples were collected on 10 d intervals during the breeding season for analysis of progesterone concentrations. Resumption of cyclicity was defined as two consecutive 1.5 ng/mL Data were analyzed using the MIXED ( BW BCS, postpartum interval) and G ENMOD (pregnancy rate) procedures of SAS. The model statement contained the effects of treatment, year, and treatment x year interaction. For postpartum interval, the model statement also included the effect of sampling time. For calf BW, the model state ment contained the effects of treatment, sex, year and all possible interactions. Since weaning treatment was applied directly to the cow or calf, cow or calf was the experimental unit for all analyses. Treatment differences were compared by single degree s of freedom contrasts predefined as EW vs. IW and CON, and IW vs. CON. Significance was set at P < 0.05. Response variables were BCS, BW, pregnancy rate and initiation of estrous. Results There was no treatment x year interaction for cow BW and there was no treatment x sex x year interaction for calf BW Cow BW at the beginning of the breeding season did not differ ( P > 0.10); however, at the end of the breeding season (d 90), EW cows were heavier ( P < 0.01) than CON and IW cows (Table 1). Cow BCS tended ( P = 0.09) to be greater for EW cows compared to CON and IW cows on d 90 (Table 1). Calf BW did not differ at the beginning of the breeding season, but was greater ( P < 0.01) for EW vs. IW and CON calves on d 90 (Table 2). In addition, C ON calves were heavier ( P = 0.05) than IW calves on d 90 (Table 2). There was no treatment x year interaction for postpartum interval or cow pregnancy rate. By

PAGE 3

d 30, more EW cows were cycling than IW and CON (89.5, 68.9, and 61.1%, respectively; P = 0.0 2). On d 90, there was a tendency ( P = 0.11) for more IW cows to be cycling compared to CON cows (94.6, 90.1, and 72.7 % cycling for EW, IW, and CON cows, respectively). Overall pregnancy rate tended ( P = 0.06) to be greater for EW vs. the average of IW and CON cows (94.4 vs. 80.7%). Additionally, pregnancy rate of IW cows was greater ( P = 0.03) than CON cows (90.1 vs. 72.7%). In summary, compared to traditional, single time, 48 h calf withdrawal, repeated 48 h calf withdrawal resulted in similar cow BW and BCS changes, reduced calf BW gain, hastened postpartum anestrus period, and greater pregnancy rate. We conclude that repeated 48 h calf withdrawal may be an effective option for the management of first calf, Brahman crossbred cows, particularly for pro ducers that are unable or unwilling to early wean (permanently separate) cows and calves at the start of the breeding season. Acknowledgments The authors thank Mr. Austin Bateman, Mr. Clay Newman and Ms. Andrea Dunlap for their technical assistan ce during the conduct of this study, and fellowship from CAPES of Brazil to Paulo G.M.A. Martins.

PAGE 4

Table 1. Least squares means of cow body weights and BCS of control (CON), interval (IW), and early weaning (EW) treatments 1 Item Control Interval weaned Early weaned SEM Contrasts (CON&IW) vs. EW CON vs. IW Cow BW, lb d 0 814 814 816 13.5 0.91 0.97 d 41 818 813 833 9.7 0.19 0.73 d 90 795 793 850 8.1 <0.01 0.80 BW gain, lb 25 27 30 8.1 <0.01 0.80 Cow BCS 2 d 0 4.3 4.6 4.5 0.16 0.28 0.20 d 90 3.9 4.0 4.7 0.23 0.09 0.85 Change 0.5 0.4 +0.2 0.23 0.09 0.85 1 EW = calves early weaned on d 0; IW = 48 h calf withdrawal, 4 times during the breeding season, 20 d apart; CON = single 48 h calf withdrawal on d 0. Treatments were initiated at the start of the breeding season (d 0; 95 20.7 d postpartum). 2 Cow bod y condition score was estimated using a nine point scale where 1 = emaciated to 9 = obese Table 2. Effect of control (CON), interval (IW) and early weaned (EW) on calf growth performance 1 Item Control Interval weaned Early weaned SEM Contrasts (CON&IW) vs. EW CON vs. IW Calf BW, lb d 0 191 207 191 6.0 0.29 0.07 d 90 292 278 377 4.7 <0.01 0.05 BW gain, lb 91 77 176 4.7 <0.01 0.05 1 EW = calves early weaned on d 0; IW = 48 h calf withdrawal, 4 times during the breeding season, 20 d apart; CON = single 48 h calf withdrawal on d 0. Treatments were initiated at the start of the breeding season (d 0; 95 20.7 d postpartum).