Comparison of a Select Synch/CIDR + timed artificial insemination vs. a modified Co-Synch/CIDR estrous synchronization p...

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Comparison of a Select Synch/CIDR + timed artificial insemination vs. a modified Co-Synch/CIDR estrous synchronization protocol in suckled Bos indicus x Bos taurus cows
Series Title:
2009 Florida Beef Report
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Book
Creator:
Esterman, Regina
Austin, Brad
McKinniss, Erin
Yelich, Joel
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Institute of Food and Agricultural Sciences, University of Florida
Place of Publication:
Gainesville, Fla.
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Comparison of a Select Synch/CIDR + Timed Artificial Insemination vs a
Modified Co-Synch/CIDR Estrous Synchronization Protocol in Suckled Bos
Indicus X Bos Taurus Cows

Regina Esterman1
Brad Austin
Erin McKinniss
Joel Yelich


Suckled Bos indicus x Bos taurus cows achieved similar synchronized pregnancy rates when
synchronized with a Select Synch/CIDR + timed artificial insemination (49.4%) vs a modified
Co-Synch/CIDR protocol (47.1%) in a large field trial with 5 groups (n=659).


Summary
Suckled Bos indicus x Bos taurus cows were
used to compare a Select Synch/CIDR + timed
artificial insemination (AI) protocol (SSC) vs a
modified Co-Synch/CIDR protocol (COS). Five
groups of suckled Bos indicus x Bos taurus cows
were evaluated (n=659). Cows received GnRH
and a CIDR on d 0. On d 7, SSC cows had their
CIDR removed and received prostaglandin F2a
(PGF2), whereas COS cows had their CIDR
removed and received PGF2, on d 7.5. Estrus
was detected for 3 following PGF2, and SSC
cows were AI 8 to 12 h after observed in estrus.
Cows on the SSC protocol not 1~,JdiIg,,in estrus
by 72 h after PGF2, were timed-AI between 76
to 80 h and received GnRH. Estrus was
detected on COS cows, but all COS cows were
timed-AI at 66 h after PGF2, and received
GnRH, regardless of whether they displayed
estrus or not. Similar (P>0.05) synchronized
pregnancy rates were achieved with the SSC
(49.4%; 164/332) and COS (47.1%; 154/327)
protocols. Differences (P<0.05) in estrous
response, timed-Al pregnancy, and synchronized
pregnancy rates were observed between groups.
Days postpartum influenced (P<0.05) timed-AI
pregnancy and synchronized pregnancy rates,
with longer postpartum cows achieving greater
pregnancy rates. Cycling status did not
(P>0.05) influence synchronized pregnancy
rates. In summary, this field trial ,,'. ,i\, that
similar pregnancy rates can be achieved using a


straight timed-AI synchronization protocol
(COS) compared to a heat detection + cleanup
timed-Al protocol (SSC).

Introduction
Development of an estrous synchronization
protocol that achieves acceptable pregnancy
rates in cattle of Bos indicus breeding is
particularly important to producers in
subtropical regions, such as Florida. While there
are many common synchronization protocols,
nearly all of them were developed for Bos taurus
cattle. A frequently used and effective
synchronization protocol in Bos taurus cattle is
administration of GnRH followed 7 d later with
PGF2,. However, a common problem with the
GnRH + PGF2, protocol is expression of estrus
several days before PGF2,, which can be
eliminated with addition of a progestogen
concomitant with GnRH and removed at PGF2z.
Addition of progestogen can also increase the
percentage of anestrous cows that exhibit estrus.
However, limited research has employed this
protocol in Bos indicus x Bos taurus cattle. The
unpredictability of these synchronization
protocols in cattle of Bos indicus breeding
makes it difficult to utilize a timed-AI program.
Behavioral differences are also apparent in cattle
of Bos indicus breeding, including a shorter, less
evident estrus and increased occurrence of
'silent estrus'. Due to the difficultly of detecting


2009 Florida BeefReport










estrus in these cattle, if a timed-AI protocol
could be refined to produce acceptable
pregnancy rates, the need for estrous detection
would be minimized.

The objective of these experiments were to
evaluate the effectiveness of a Select
Synch/CIDR synchronization protocol followed
by either 3 d of estrous detection with a cleanup
timed-AI at 75 to 80 h or a straight timed-AI at
66 h in postpartum lactating Bos indicus x Bos
taurus cows.

Materials and Methods
This experiment was conducted from January to
May, 2008 at the Bar L Ranch, Marianna, FL
and the University of Florida Beef Research
Unit, Gainesville, FL. Five groups of
primiparous and multiparous postpartum
lactating Bos indicus x Bos taurus cows (n=659)
were used. Groups were pre-selected by the
location and initiated the synchronization
protocol once they reached > 45 days
postpartum. Mean (+ SD) cow age was 5.3 +
2.4 yr, DPP was 69.2 15.0 d, body weight
(BW) was 1181 + 154 lb, and body condition
score was 5.3 0.6 (Table 1; BCS: 1
emaciated, 9 = obese). Cycling status, BCS, and
DPP for each group is described in Table 1. The
degree of Bos indicus breeding ranged from
approximately 10 to 75% with the remainder
being Bos taurus breeding. Three groups of
cows were started on the experiment protocol in
three consecutive wk at Bar L Ranch and two
groups were started on the experimental protocol
three wk apart at the Beef Research Unit. On d
0, BW and BCS were evaluated and on d 0 and
10 blood samples were collected for
determination of cycling status. At the start of
the synchronization (d 10), cows were equally
distributed by cow age, DPP, and BCS to one of
two treatments, which included Select
Synch/CIDR + timed-AI (SSC) and a modified
Co-Synch/CIDR (COS) protocol. All cows
received GnRH (100 ig i.m.; Cystorelin,
Merial) at CIDR (1.38 g progesterone; Eazi-
BreedTM CIDR, Pfizer Animal Health)
insertion. On d 7, SSC cows' CIDR were
removed and cows received PGF2, (25 mg i.m.;
Lutalyse, Pfizer Animal Health). On d 7.5,
COS cows' CIDR were removed and cows


received PGF2a. All cows received an estrous
detection patch (Estrotect Rockway, Inc.) at
CIDR removal to aid in estrous detection.

Estrus was visually detected in both treatments
two times daily at 0700 and 1700 h for 3 d
following PGF2,. Estrus was defined as a cow
standing to be mounted by another cow and/or a
half to fully rubbed EstrotectT patch. Cows in
the SSC treatment were AI 8 to 12 h after
observed in estrus through 72 h post-PGF2z
Cows in the SSC that had not displayed estrus
by 0800 h, 73 h after PGF2a, were timed-AI and
administered GnRH between 76 and 80 h after
PGF2,. Cows in the COS treatment were all
timed-AI at 66 h after PGF2a and administered
GnRH.

Frozen-thawed semen from multiple AI sires
was used and cows were inseminated by four AI
technicians. In four of the five groups, 7 d after
the last cow was inseminated, clean-up bulls
were placed with cows. In the remaining group,
estrous detection continued for 30 d and cows
displaying estrus were inseminated a second
time. Pregnancy was diagnosed approximately
55 d after AI using a real-time B-mode
ultrasonography machine (Aloka 500V,
Corometrics Medical Systems) with a 5.0 MHz
transducer. Due to the 7 d period in which no
cows were inseminated or bred by the clean-up
bull, differences in fetal size were used to
determine whether a pregnancy resulted from
the synchronized breeding or clean-up bull.

The GENMOD procedure of SAS (SAS Inst.
Inc.) was used for the statistical analysis of this
experiment. The effects of treatment, group, and
their interaction, were evaluated for estrous
response, conception, timed-AI pregnancy,
synchronized pregnancy, and thirty-day
pregnancy rates. Cow age, DPP, BCS, and
interval from PGF2a to the onset of estrus were
included as covariates. When covariates were
significant (P < 0.05) they were treated as
independent variables.

Results
Estrous response over 3 d following PGF2, for
the SSC cows was 50.6% (168/332) and estrous
response for the 2.5 d following PGF2, for the


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Table 1 General description of Bos indicus x Bos taurus cows synchronized with either a Select
Synch/CIDR + TAI or modified Co-Synch/CIDR synchronization protocol by group.a

Cycling Status Approx. % Body condition Days postpartum,
Group n (%) Brahman breeding score, 1-9, (range) (range)
(%)

59.0 (173) 10 38 5.4 + 0.05 74.0 + 1.1
(3.5-7.0) (48- 128)

38.2 (152) 10 -38 5.2 + 0.05 75.4 + 1.2
(4.0-7.0) (47- 102)

59.6 (193) 10 -38 5.5 + 0.05 62.8 + 1.0
(4.0-7.0) (54-99)

64.9 (94) 25 -75 5.1 + 0.1 71.3 + 1.4
(3.5-6.5) (50-99)

66.0 (47) 25 -75 5.1 + 0.1 53.8 + 2.0
(3.5-6.5) (41 -69)

a All cows received GnRH at initiation of the 7 d CIDR treatment, with PGF2, administered at the time of
CIDR removal. For Select Synch/CIDR + TAI cows, estrus was detected for 3 d, and cows that exhibited
estrus were AI approximately 8 to 12 h later. Cows which had not displayed estrus were timed-AI at 76 to
80 h and given GnRH. All modified Co-Synch/CIDR cows were fixed TAI at 66 h after PGF2a.


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Table 2 Effect of synchronization protocol (Select Synch/CIDR + timed-AI (SCC) or modified Co-
Synch/CIDR (COS)) and cycling status on estrous response, conception, timed-AI pregnancy, and
synchronized pregnancy rates following PGF2, in Bos indicus x Bos taurus cows.a

Estrous Conception rate, Timed-AI Synchronized
Treatment n response, %b %o pregnancy rate, pregnancy rate,
%d %e


SSC


Cycling


Non-cycling


COS


Cycling


Non-cycling


P Values

Treatment


Cycling Status


Treatment x Cycling


332 50.6 (332)


185 48.8 (185)


147 59.2 (147)


327 52.6 (327)


182 48.9(182)


145 57.2 (145)


P > 0.05

P < 0.05

P > 0.05


a All cows received GnRH at initiation of the 7 d CIDR treatment, with PGF2a administered at the time of
CIDR removal. For Select Synch/CIDR + TAI cows, estrus was detected for 3 d, and cows that exhibited
estrus were AI approximately 8 to 12 h later. Cows which had not displayed estrus were timed-AI at 76 to
80 h and given GnRH. All modified Co-Synch/CIDR cows were fixed TAI at 66 h after PGF2a.
b Percentage of cows displaying estrus 3 d after PGF2a of total treated.
' Percentage of cows pregnant to AI of the total that exhibited estrus and were AI.
d Percentage of cows pregnant to timed-AI of the total that were timed-AI.
e Percentage of cows pregnant during the synchronized breeding of the total treated.


2009 Florida BeefReport


66.1 (168)


66.7 (81)


65.5 (87)


P > 0.05


32.3 (164)


40.4 (104)


18.3 (60)


47.1(327)


45.1(182)


49.7 (145)


P > 0.05


49.4 (332)


51.9(185)


46.3 (147)


47.1 (327)


45.1 (182)


49.7 (145)


P > 0.05

P > 0.05

P > 0.05















Table 3 Effect of days postpartum (DPP) on estrous response, conception, timed-AI pregnancy, and
synchronized pregnancy rates following PGF2a in Bos indicus x Bos taurus cows synchronized with
either a Select Synch/CIDR + timed-AI (SCC) or modified Co-Synch/CIDR (COS) synchronization
protocol.a

Estrous Conception rate, Timed-AI Synchronized
DPP n response, %b %c pregnancy rate, pregnancy rate,
%d %e

<55 d 96 35.4 (96) 70.6(17) 31.6(79)fh 38.5 (96)'


56-65 228 50.4 (228)g 70.4 (54) 47.7 (174)g 53.1 (228)g
56 65


6675 148 60.1 (148)h 56.5 (46) 50.0 (102)g 52.0 (148)g,h
66 75


136 54.6 (187)g,h 68.6 (51) 35.3 (136)h 44.4 (187)fh
> 76 d




P Values P < 0.05 P > 0.05 P < 0.05 P < 0.05

a All cows received GnRH at initiation of the 7 d CIDR treatment, with PGF2a administered at the time of
CIDR removal. For Select Synch/CIDR + TAI cows, estrus was detected for 3 d, and cows that exhibited
estrus were AI approximately 8 to 12 h later. Cows which had not displayed estrus were timed-AI at 76 to
80 h and given GnRH. All modified Co-Synch/CIDR cows were fixed TAI at 66 h after PGF2a.
b Percentage of cows displaying estrus 3 d after PGF2a of total treated.
' Percentage of cows pregnant to AI of the total that exhibited estrus and were AI.
d Percentage of cows pregnant to timed-AI of the total that were timed-AI.
e Percentage of cows pregnant during the synchronized breeding of the total treated.
f,gh Means without a common superscript within a column differ (P<0.05).


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Table 4 Effect of body condition score (BCS) on estrous response, conception, timed-AI pregnancy,
and synchronized pregnancy rates following PGF2a in Bos indicus x Bos taurus cows synchronized
with either a Select Synch/CIDR + timed-AI (SCC) or modified Co-Synch/CIDR (COS)
synchronization protocol.a

Estrous Conception rate, Timed-AI Synchronized
BCS n response, %b %c pregnancy rate, pregnancy rate,
%d %e

< 4.5 118 41.5 (118)' 54.6(22) 35.4(96) 39.0 (118)


5 -375 53.6 (375)g 63.7 (102) 43.2 (273) 48.8 (375)g


6 166 54.2 (166)g 77.3(44) 45.1(122) 53.6 (166)g
>6




P Values P = 0.05 P > 0.05 P > 0.05 P < 0.05

a All cows received GnRH at initiation of the 7 d CIDR treatment, with PGF2a administered at the time of
CIDR removal. For Select Synch/CIDR + TAI cows, estrus was detected for 3 d, and cows that exhibited
estrus were AI approximately 8 to 12 h later. Cows which had not displayed estrus were timed-AI at 76 to
80 h and given GnRH. All modified Co-Synch/CIDR cows were fixed TAI at 66 h after PGF2a.
b Percentage of cows displaying estrus 3 d after PGF2a of total treated.
C Percentage of cows pregnant to AI of the total that exhibited estrus and were AI.
d Percentage of cows pregnant to timed-AI of the total that were timed-AI.
e Percentage of cows pregnant during the synchronized breeding of the total treated.

f g Means without a common superscript within a column differ (P<0.05).


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54 2009 Florida BeefReport




Full Text

PAGE 1

Comparison o f a Select Synch / CIDR + Timed Artificial Insemination v s a Modified Co Synch / CIDR Estrous Synchronization Protocol i n Suckled Bos Indicus Bos Taurus Cows Regina Esterman 1 Brad Austin Erin McKinniss Joel Yelich Summary Suckled Bos indicus Bos taurus cows were used to compare a Select Synch/CIDR + timed artificial insemination (AI) protocol (SSC) vs a modified Co-Synch/CIDR protocol (COS). Five groups of suckled Bos indicus Bos taurus cows were evaluated (n=659). Cows received GnRH and a CIDR on d 0. On d 7, SSC cows had their CIDR removed and received prostaglandin F (PGF ), whereas COS cows had their CIDR removed and received PGF on d 7.5. Estrus was detected for 3 d following PGF and SSC cows were AI 8 to 12 h after observed in estrus. Cows on the SSC protocol not exhibiting estrus by 72 h after PGF were timed-AI between 76 to 80 h and received GnRH. Estrus was detected on COS cows, but all COS cows were timed-AI at 66 h after PGF and received GnRH, regardless of whether they displayed estrus or not. Similar (P>0.05) synchronized pregnancy rates were achieved with the SSC (49.4%; 164/332) and COS (47.1%; 154/327) protocols. Differences (P<0.05) in estrous response, timed-AI pregnancy, and synchronized pregnancy rates were observed between groups. Days postpartum influenced (P<0.05) timed-AI pregnancy and synchronized pregnancy rates, with longer postpartum cows achieving greater pregnancy rates. Cycling status did not (P>0.05) influence synchronized pregnancy rates. In summary, this field trial suggests that similar pregnancy rates can be achieved using a straight timed-AI synchronization protocol (COS) compared to a heat detection + cleanup timed-AI protocol (SSC). Introduction Development of an estrous synchronization protocol that achieves acceptable pregnancy rates in cattle of Bos indicus breeding is particularly important to producers in subtropical regions, such as Florida. While there are many common synchronization protocols, nearly all of them were developed for Bos taurus cattle. A frequently used and effective synchronization protocol in Bos taurus cattle is administration of GnRH followed 7 d later with PGF However, a common problem with the GnRH + PGF protocol is expression of estrus several days before PGF which can be eliminated with addition of a progestogen concomitant with GnRH and removed at PGF Addition of progestogen can also increase the percentage of anestrous cows that exhibit estrus. However, limited research has employed this protocol in Bos indicus Bos taurus cattle. The unpredictability of these synchronization protocols in cattle of Bos indicus breeding makes it difficult to utilize a timed-AI program. Behavioral differences are also apparent in cattle of Bos indicus breeding, including a shorter, less evident estrus and increased occurrence of Suckled Bos indicus Bos taurus cows achieved similar synchronized pregnancy rates when synchronized with a Select Synch/CIDR + timed artificial insemination (49.4%) vs a modified Co Synch/CIDR protocol (47.1%) in a large field trial with 5 groups (n=659).

PAGE 2

estrus in these cattle, if a timed-AI protocol could be refined to produce acceptable pregnancy rates, the need for estrous detection would be minimized. The objective of these experiments were to evaluate the effectiveness of a Select Synch/CIDR synchronization protocol followed by either 3 d of estrous detection with a cleanup timed-AI at 75 to 80 h or a straight timed-AI at 66 h in postpartum lactating Bos indicus Bos taurus cows. Materials and Methods This experiment was conducted from January to May 2008 at the Bar L Ranch, Marianna, FL and the University of Florida Beef Research Unit, Gainesville, FL. Five groups of primiparous and multiparous postpartum lactating Bos indicus Bos taurus cows (n=659) were used. Groups were pre-selected by the location and initiated the synchronization protocol once they reached > 45 days postpartum. Mean ( SD) cow age was 5.3 2.4 yr, DPP was 69.2 15.0 d, body weight (BW) was 1181 154 lb, and body condition score was 5.3 0.6 (Table 1; BCS: 1 = emaciated, 9 = obese). Cycling status, BCS, and DPP for each group is described in Table 1. The degree of Bos indicus breeding ranged from approximately 10 to 75% with the remainder being Bos taurus breeding. Three groups of cows were started on the experiment protocol in three consecutive wk at Bar L Ranch and two groups were started on the experimental protocol three wk apart at the Beef Research Unit. On d 0, BW and BCS were evaluated and on d 0 and 10 blood samples were collected for determination of cycling status. At the start of the synchronization (d 10), cows were equally distributed by cow age, DPP, and BCS to one of two treatments, which included Select Synch/CIDR + timed-AI (SSC) and a modified Co -Synch/CIDR (COS) protocol. All cows received GnRH (100 g i.m.; Cystorelin Merial) at CIDR (1.38 g progesterone; Eazi, Pfizer Animal Health) removed and cows received PGF (25 mg i.m.; Lu talyse Pfizer Animal Health). On d 7.5, received PGF All cows received an estrous detection patch (Estrotect Rockway, Inc.) at CIDR removal to aid in estrous detection. Estrus was visually detected in both treatments two times daily at 0700 and 1700 h for 3 d following PGF Estrus was defined as a cow standing to be mounted by another cow and/or a half to fully rubbed Estrotect patch. Cows in the SSC treatment were AI 8 to 12 h after observed in estrus through 72 h post-PGF Cows in the SSC that had not displayed estrus by 0800 h, 73 h after PGF were timed-AI and administered GnRH between 76 and 80 h after PGF Cows in the COS treatment were all timed-AI at 66 h after PGF and administered GnRH. Frozen-thawed semen from multiple AI sires was used and cows were inseminated by four AI technicians. In four of the five groups, 7 d after the last cow was inseminated, clean-up bulls were placed with cows. In the remaining group, estrous detection continued for 30 d and cows displaying estrus were inseminated a second time. Pregnancy was diagnosed approximately 55 d after AI using a real-time B-mode ultrasonography machine (Aloka 500V, Corometrics Medical Systems) with a 5.0 MHz transducer. Due to the 7 d period in which no cows were inseminated or bred by the clean-up bull, differences in fetal size were used to determine whether a pregnancy resulted from the synchronized breeding or clean-up bull. The GENMOD procedure of SAS (SAS Inst. Inc.) was used for the statistical analysis of this experiment. The effects of treatment, group, and their interaction, were evaluated for estrous response, conception, timed-AI pregnancy, synchronized pregnancy, and thirty-day pregnancy rates. Cow age, DPP, BCS, and interval from PGF to the onset of estrus were included as covariates. When covariates were significant (P < 0.05) they were treated as independent variables. Results Estrous response over 3 d following PGF for the SSC cows was 50.6% (168/332) and estrous response for the 2.5 d following PGF for the

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COS cows was 52.6% (172/327; Table 2). Estrous response was different ( P <0.05) for groups (data not shown). Estrous response was influenced ( P <0.05) by cycling status at the start of synchronization (Table 2), with a greater percent of noncycling cows displaying estrus (58.2%; 170/292) compared to cycling cows (46.3%; 170/367). Days postpartum effected ( P <0.05) estrous response (Table 3). Cows that P <0.05) estrous respo Cows that were 56 to 65 DPP had a lower ( P <0.05) estrous response compared to cows that were 66 to 75 DPP, but were similar ( P P >0.05) estrous response. Body condition score influenced ( P <0.05) estrous response (Table 4). P <0.05) estrous response compared to cows with 5 to 5.5 P >0.05) estrous response. There were no ( P >0.05) effects of age on estrous response. In SSC cows that displayed estrus, the interval from PGF to the onset of estrus was 59.1 0.7 h. In COS cows that displayed estrus, the interval from PGF to the onset of estrus was 51.0 0.7 h. The conception rate for SSC cows was 66.1% (111/168; Table 2). Conception rate was not ( P >0.05) effected by group. Cycling status, age, and DPP did not ( P >0.05) effect conception rate in SSC cows. In SSC cows that did not display estrous and were timed-AI, timed-AI pregnancy rate averaged 32.3% (53/164) across all groups (Table 2). In COS cows, all cows were timedAI and the timed-AI pregnancy rate averaged 47.1% (154/327) across all groups. Timed-AI pregnancy rates differed ( P <0.05) between groups (data not shown). Days postpartum influenced ( P <0.05) timed-AI pregnancy rate ( P <0.05) timed-AI pregnancy rates compared to cows that were 56 to 65 DPP and 66 to 75 DPP, 65 DPP and 66 to 75 DPP had similar ( P >0.05) timed-AI pregnancy rates, but were both greater ( P Timed-AI pregnancy rate was not ( P >0.05) effected by cycling status, age, or BCS. Synchronized pregnancy rates were similar ( P>0.05) for SSC (49.4%; 164/332) and COS (47.1%; 154/327) treatments (Table 2). Groups differed ( P <0.05) in synchronized pregnancy rates (data not shown). Cycling status did not ( P>0.05) influence overall synchronized pregnancy rates. Days postpartum influenced ( P<0.05) synchronized pregnancy rates (Table ( P<0.05) synchronized pregnancy rates compared to cows that were 56 to 65 DPP and 66 to 75 DPP, but were similar ( P >0.05) to cows d 66 to 75 DPP had similar ( P >0.05) synchronized pregnancy rates, as did cows that were 65 to 75 P >0.05) synchronized pregnancy rates. Body condition score influenced ( P <0.05) synchronized 4.5 (39.0; 46/118) had lower ( P <0.05) synchronized pregnancy rates compared to cows (53.6%; 89/166). Cows with a BCS of 5 to 5.5 P >0.05) synchronized pregnancy rates. Synchronized pregnancy rate was not ( P >0.05) influenced by cow age. In summary, similar synchronized pregnancy rates were achieved using the SSC and COS synchronization protocols. Differences in estrous response, timed-AI pregnancy, and synchronized pregnancy rates were observed between groups. Cycling status did not influence pregnancy rates, however DPP did effect pregnancy rates. 1 Regina Esterman ; Graduate Student; Brad Austin, Graduate Student; Erin McKinniss; Graduate Student; Joel Yelich Associate Professor, UF IFAS Animal Sciences, Gainesville, FL

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Table 1 General description of Bos indicus Bos taurus cows synchronized with either a Select Synch/CIDR + TAI or modified Co Synch/CIDR synchronization protocol by group. a Group n Cycling Status (%) Approx. % Brahman breeding (%) Body condition score, 1 9, (range) Days postpartum, (range) 1 173 59.0 (173) 10 38 5.4 0.05 (3.5 7.0) 74.0 1.1 (48 128) 2 152 38.2 (152) 10 38 5.2 0.05 (4.0 7.0) 75.4 1.2 (47 102) 3 193 59.6 (193) 10 38 5.5 0.05 (4.0 7.0) 62.8 1.0 (54 99) 4 94 64.9 (94) 25 75 5.1 0.1 (3.5 6.5) 71.3 1.4 (50 99) 5 47 66.0 (47) 25 75 5.1 0.1 (3.5 6.5) 53.8 2.0 (41 69) a All cows received GnRH at initiation of the 7 d CIDR treatment, with PGF 2 administered at the time of CIDR removal. For Select Synch/CIDR + TAI cows, estrus was detected for 3 d, and cows that exhibited estrus were AI approximately 8 to 12 h later. Cows which had not displayed estrus were timed AI at 76 to 80 h and given GnRH All modified Co Synch/CIDR cows were fixed TAI at 66 h after PGF 2

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Table 2 Effect of synchronization protocol ( Select Synch/CIDR + timed AI (SCC) or modified Co Synch/CIDR (COS)) and cycling status on e strous response, conception, timed AI pregnancy, and synchronized pregnancy rates following PGF 2 in Bos indicus Bos taurus cows. a Treatment n Estrous response, % b Conception rate, % c Timed AI pregnancy rate, % d Synchronized pregnancy rate, % e SSC 332 50 .6 (332) 66.1 (168) 32.3 (164) 49.4 (332) Cycling 185 48.8 (185) 66.7 (81) 40.4 (104) 51.9 (185) Non cycling 147 59.2 (147) 65.5 (87) 18.3 (60) 46.3 (147) COS 327 52.6 (327) 47.1 (327) 47.1 (327) Cycling 182 48.9 (182) 45.1 (182) 45.1 (182) Non cycling 145 57.2 (145) 49.7 (145) 49.7 (145) P Values Treatment P > 0.05 . P > 0.05 Cycling Status P < 0.05 P > 0.05 P > 0.05 P > 0.05 Treatment Cycling P > 0.05 . P > 0.05 a All cows received GnRH at initiation of the 7 d CIDR treatment, with PGF 2 administered at the time of CIDR removal. For Select Synch/CIDR + TAI cows, estrus was detected for 3 d, and cows that exhibited estrus were AI approximately 8 to 12 h later. Cows which had not displayed estrus were timed AI at 76 to 80 h and given GnR H. All modified Co Synch/CIDR cows were fixed TAI at 66 h after PGF 2 b Percentage of cows displaying estrus 3 d after PGF 2 of total treated. c Percentage of cows pregnant to AI of the total that exhibited estrus and were AI. d Percentage of cows pregnant to timed AI of the total that were timed AI. e Percentage of cows pregnant during the synchronized breeding of the total treated.

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Table 3 Effect of days postpartum (DPP) on estrous response, conception, timed AI pregnancy, and synchronized pregnancy rates following PGF 2 in Bos indicus Bos taurus cows synchronized with either a Select Synch/CIDR + timed AI (SCC) or modified Co Synch/CIDR (COS) synchronization protocol. a DPP n Estrous response, % b Conception rate, % c Timed AI pregnancy rate, % d Synchronized pregnancy rate, % e 96 35.4 (96) f 70.6 (17) 31.6 (79) f,h 38.5 (96) f 56 65 228 50.4 (228) g 70.4 (54) 47.7 (174) g 53.1 (228) g 66 75 148 60.1 (148) h 56.5 (46) 50.0 (102) g 52.0 (148) g,h 136 54.6 (187) g,h 68.6 (51) 35.3 (136) h 44.4 (187) f,h P Values P < 0.05 P > 0.05 P < 0.05 P < 0.05 a All cows received GnRH at initiation of the 7 d CIDR treatment, with PGF 2 administered at the time of CIDR removal. For Select Synch/CIDR + TAI cows, estrus was detected for 3 d, and cows that exhibited estrus were AI approximately 8 to 12 h later. Cows which had not displayed estrus were timed AI at 76 to 80 h and given GnRH All modified Co Synch/CIDR cows were fixed TAI at 66 h after PGF 2 b Percentage of cows displaying estrus 3 d after PGF 2 of total treated. c Percentage of cows pregnant to AI of the total that exhibited estrus and were AI. d Percentage of cows pregnant to timed AI of the total that were timed AI. e Percentage of cows pregnant during the synchronized breeding of the total treated. f,g,h Means without a common superscript within a column differ (P<0.05).

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Table 4 Effect of body condition score (BCS) on estrous response, conception, timed AI pregnancy, and synchronized pregnancy rates following PGF 2 in Bos indicus Bos taurus cows synchronized with either a Select Synch/CIDR + timed AI (SCC) or modified Co Synch/CIDR (COS) synchronization protocol. a BCS n Estrous response, % b Conception rate, % c Timed AI pregnancy rate, % d Synchronized pregnancy rate, % e 118 41.5 (118) f 54.6 (22) 35.4 (96) 39.0 (118) f 5 5.5 375 53.6 (375) g 63.7 (102) 43.2 (273) 48.8 (375) g 166 54.2 (166) g 77.3 (44) 45.1 (122) 53.6 (166) g P Values P = 0.05 P > 0.05 P > 0.05 P < 0.05 a All cows received GnRH at initiation of the 7 d CIDR treatment, with PGF 2 administered at the time of CIDR removal. For Select Synch/CIDR + TAI cows, estrus was detected for 3 d, and cows that exhibited estrus were AI approximately 8 to 12 h later. Cow s which had not displayed estrus were timed AI at 76 to 80 h and given GnRH. All modified Co Synch/CIDR cows were fixed TAI at 66 h after PGF 2 b Percentage of cows displaying estrus 3 d after PGF 2 of total treated. c Percentage of cows pregnant to AI of the total that exhibited estrus and were AI. d Percentage of cows pregnant to timed AI of the total that were timed AI. e Percentage of cows pregnant during the synchronized breeding of the total treated. f,g Means without a common superscript withi n a column differ (P<0.05).