Evaluation of a new or once-used CIDR and two different prostaglandin F2a treatments to synchronize suckled Bos indicus ...

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Evaluation of a new or once-used CIDR and two different prostaglandin F2a treatments to synchronize suckled Bos indicus x Bos taurus cows
Series Title:
2009 Florida Beef Report
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Book
Creator:
Esterman, Regina D.
Austin, Brad R.
Woodall, Steaven A.
Hansen, Gary R.
Hersom, Matt
Yelich, Joel V.
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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 a New or Once-used CIDR and Two Different Prostaglandin F2a
Treatments to Synchronize Suckled Bos indicus x Bos taurus Cows

Regina D. Esterman1
Brad R. Austin
Steaven A. Woodall
Gary R. Hansen
Matt Hersom
Joel V. Yelich


Suckled Bos indicus x Bos taurus cows achieved similar pregnancy rates when synchronized with CIDR
inserts and two PGF2, types. Greater synchronized pregnancy rates were observed with a 3 d estrous
detection and clean-up timed artificial insemination compared to a 5 d estrous detection following
PGF2,. Days from calving had a strong influence on response to synchronization protocol.


Summary
Multiparous suckled Bos indicus x Bos taurus
cows were used in two experiments to evaluate
the Select Synch and Select Synch + timed
artificial insemination (TAI) synchronization
protocols combined with a controlled
intravaginal progesterone device (CIDR). Both
experiments were conducted as 2 x 2 factorial
designs with the main effects being CIDR type
(new vs once-used) and PGF2a type
(cloprostenol sodium vs dinoprost
tromethamine). Cows in both experiments
received GnRH and either a new CIDR or once-
used CIDR on d 0, followed by CIDR removal
and either cloprostenol sodium or dinoprost
tromethamine on d 7. In Exp. 1, estrus was
detected for 5 following PGF2a and cows were
AI 8 to 12 h after observed in estrus. In Exp. 2,
estrus was detected for 3 following PGF2a and
cows were AI 8 to 12 h after observed in estrus.
Cows not %hdml,.iinmg estrus by 72 h after PGF2a
were timed-AI between 76 to 80 h and received
GnRH. In Exp. 1, estrous response, conception,
and synchronized pregnancy rates were similar
(P>0. 05) for both new and once-used CIDR, as
well as cloprostenol sodium and dinoprost
tromethamine. Interval from PGF2a to onset of
estrus influenced (P<0.05) conception rates.
Cows displaying estrus < 84 h after PGF2a had
greater (P<0.05) conception rates compared to


cows %hi,.h,,in estrus > 96 h after PGF2a. In
Exp. 2, estrous response, conception, timed-AI,
and synchronized pregnancy rates were similar
(P>0.05) for new and once-used CIDR, as well
as cloprostenol sodium and dinoprost
tromethamine. In both experiments, estrous
response, conception, and pregnancy rates
increased (P<0.05) as days from calving
increased. In summary, CIDR (new vs once-
used) and PGF2a (cloprostenol sodium vs
dinoprost tromethamine) types resulted in
similar responses when used in the Select Synch
protocol and the response to synchronization
treatment increased as days from calving
increased in suckled Bos indicus x Bos taurus
cows.

Introduction
Estrous synchronization allows for more cows to
display estrus and ovulate over a period of
several days. This allows for either a reduction
of daily estrous detection over a 21 d estrous
cycle to 1 to 5 d, or elimination of estrous
detection and insemination of all cows at a pre-
determined time known as timed-AI. A
frequently used and effective synchronization
protocol in Bos taurus cattle is administration of
GnRH followed 7 d later with PGF2a. However,
a common problem with the GnRH + PGF2a


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protocol is that some cattle express estrus
several days before PGF2a, which requires
additional estrous detection. This problem can
be eliminated with addition of a progestogen
between the GnRH and PGF2, treatments. An
added benefit of the progestogen is that it can
induce estrous cycles in some anestrous cows.
Limited research has been conducted using the
GnRH + PGF2, protocols in Bos indicus x Bos
taurus cattle either with or without a
progestogen and that research was met with
limited success. The reasons) for the less than
acceptable results are unclear, but may be due to
a decreased synchronized estrous response,
which may be influenced by decreased luteolytic
actions of PGF2a.

Several studies have reported similar responses
in Bos taurus cattle synchronized with
synchronization systems that compared
cloprostenol sodium to dinoprost tromethamine,
but limited work has been done in Bos indicus x
Bos taurus cows.

The CIDR is an effective synchronization agent
that induces estrus in some anestrous cattle. A
new CIDR (1.9 g progesterone) maintains
circulating progesterone concentrations > 1
ng/mL for at least 15 d after insertion,
suggesting that a CIDR could be used for two
consecutive 7 d treatments and still suppress
estrus. Furthermore, autoclaving a once-used
CIDR brings more progesterone to the surface
making more available for absorption in the
vagina, as well as decreasing the possibility of
disease transmission. Re-use of the CIDR could
help producers decrease the cost of
synchronizing cattle, but it must be
accomplished without a reduction in AI
pregnancy rates. Evaluation of a once-used
CIDR has not been conducted in suckled Bos
indicus x Bos taurus cows.


Therefore, the objectives of these experiments
were to evaluate the effectiveness of a new
CIDR compared to a once-used CIDR and
cloprostenol sodium compared to dinoprost
tromethamine in two GnRH + PGF2,


synchronization protocols in suckled Bos indicus
x Bos taurus cows.

Materials and Methods
Two experiments were conducted from January
to March during two successive years at the Bar
L Ranch in Marianna, FL. In Experiment 1,
multiparous, suckled Bos indicus x Bos taurus
cows (n = 284) were used. Mean (+ SD) cow
age was 5.7 1.9 yr, days postpartum (DPP)
was 58.0 12.5 d, body weight (BW) was 1098
106 lbs, and body condition score was 5.2
0.5 (BCS: 1 = emaciated, 9 = obese). The
percentage of Bos indicus breeding ranged from
approximately 10 to 38% with the remainder
being Bos taurus breeding. The experiment was
a 2 x 2 factorial design. At the start of the
experiment (d 0), cows were equally distributed
by DPP and cow age to one of two progesterone
treatments, which included a new CIDR (1.38 g;
Eazi-BreedTM CIDR, Pfizer Animal Health)
and a once-used CIDR (new CIDR used once
and autoclaved before the second use). All cows
received GnRH (100 ig i.m.; Fertagyl,
Intervet) at CIDR insertion and BCS were
recorded. On d 7, CIDR were removed and
cows within each CIDR treatment were equally
distributed by DPP, BCS, and cow age to
receive either cloprostenol sodium (cloprostenol;
500 ig i.m.; Estrumate, Schering-Plough
Veterinary Corp.) or dinoprost tromethamine
(dinoprost; 25 mg i.m.; Prostamate, Agrilabs).
All cows received an EstrotectTM estrous
detection patch (EstrotectTM, Rockway, Inc.) at
CIDR removal to aid in estrous detection.


Estrus was visually detected three times daily at
0700, 1200, and 1700 h for 5 d following PGF2a.
Estrus was defined as a cow standing to be
mounted by another cow and/or a half to full red
EstrotectTM patch. Cows were AI 8 to 12 h after
observed in estrus. Frozen-thawed semen from
a single sire of known fertility was used and
cows were inseminated by two AI technicians.
Seven d after the last cow was inseminated, bulls
were placed with cows. Pregnancy was
diagnosed approximately 55 d after AI using a
real-time B-mode ultrasonography machine


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(Aloka 500V, Corometrics Medical Systems)
with a 5.0 MHz transducer. Because there
was a 7-d period where cows were neither
inseminated nor exposed to bulls, differences in
fetal size were used to determine whether a
pregnancy resulted from the synchronized
breeding or clean-up bull.

In Experiment 2, multiparous suckled Bos
indicus x Bos taurus cows (n = 259) were used.
Mean (+ SD) cow age was 6.9 1.9 yr, DPP
was 48.5 12.8 d, and BCS was 5.1 0.5. The
experiment was a 2 x 2 factorial design and
animals were assigned to the same
synchronization treatments as Experiment 1.
Estrus was detected for 72 h following PGF2, as
described in Experiment 1. Cows were AI 8 to
12 h after observed in estrus. All cows that had
not displayed estrus by 73 h after PGF2, were
timed-AI and received GnRH between 76 and 80
h after PGF2a. Cows were inseminated by a
single AI technician with frozen-thawed semen
from five sires that were pre-assigned to cows
before AI by the co-operating producer. Seven
days after the last cow was inseminated, bulls
were placed with cows and pregnancy was
diagnosed as described in Experiment 1. The
GENMOD procedure of SAS (SAS Inst. Inc.)
was used for the statistical analysis. The main
effects of CIDR and PGF2, treatments, and
CIDR x PGF2, were evaluated for estrous
response, conception, synchronized pregnancy,
and thirty-day pregnancy rates. Cow age, DPP,
BCS, and interval from PGF2, to the onset of
estrus were included as covariates. When
covariates were significant (P < 0.05), they were
treated as independent variables.

Results
In Experiment 1, estrous response, conception
rate, and synchronized pregnancy rates were
similar (P>0.05) for main effects of CIDR and
PGF2a treatments, as well as the simple
treatment effects (Table 1). Thirty-day
pregnancy rates were similar (P>0.05) for the
new (78.0%) compared to the once-used
(79.4%) CIDR treatment and for the
cloprostenol (77.3%) compared to the dinoprost


(80.1%) treatment.

Days post partum effected (P<0.05) estrous
response, conception, and synchronized
pregnancy rates (Table 2). Cows that were long
(> 70 d) postpartum had a greater (P<0.05)
estrous response compared to cows that were
short (< 50 d) and medium (50 to 69 d)
postpartum, which were similar (P>0.05).
Conception rates were similar (P>0.05) for cows
that were medium and long postpartum, both of
which were greater (P<0.05) compared to short
postpartum cows. Synchronized pregnancy rates
were greater (P<0.05) for cows that were long
postpartum compared to short and medium
postpartum cows, which were different (P<0.05)
from each other. Thirty-day pregnancy rates
were greater (P<0.05) for cows that were
medium (79.1%) and long (87.8%) postpartum
compared to cows that were short (71.6%)
postpartum. Cows that were medium and short
postpartum had similar (P>0.05) thirty-day
pregnancy rates.

No cows were detected in estrus until 48 h after
PGF2, for any of the four treatments. The mean
interval from PGF2, to onset of estrus (64.4
16.0 h) was not influenced (P>0.05) by main or
simple treatment effects. Interestingly, there
was an effect (P < 0.01) of interval from PGF2a
to onset of estrus on conception rate (Figure 1).
Cows which displayed estrus 48, 60, 72, and 84
h after PGF2a had similar (P>0.05) conception
rates, but cows which displayed estrus at 48, 60,
and 72 h had greater (P<0.05) conception rates
compared to cows that displayed estrus 96 h
after PGF2,. Cows that displayed estrus at 84 h
had similar (P>0.05) conception rates compared
to cows which displayed estrus at 96 h. Cow
age and BCS did not affect (P>0.05) estrous
response, conception rate, synchronized
pregnancy, or 30-d pregnancy rates when
included as covariates for main and simple
treatment effects.

In Experiment 2, estrous response, conception
rate, timed-AI pregnancy, and synchronized
pregnancy rates were similar (P>0.05) for main


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effects of CIDR and PGF2~ treatments (Table
3). Thirty-day pregnancy rates were similar
(P>0.05) for the new (83.2%) compared to the
once-used (76.9%) CIDR treatment and for the
cloprostenol (76.7%) compared to the dinoprost
(83.3%) treatment.

The CIDR treatment tended (P=0.10) to
influence conception rate as 14.1% more cows
that received a new CIDR became pregnant
compared to cows that received a once-used
CIDR (Table 3). The interval from PGF2a to
onset of estrus was not (P>0.05) affected by
treatment, with a mean interval of 58.6 + 10.3 h
across the four treatments. Interval from PGF2a
to onset of estrus did not (P>0.05) effect
conception rates. Conception rates for cows that
exhibited estrus 48, 60 and 72 h after PGF2a
were 61.8 (n=55), 57.6 (n=33), and 60.0%
(n=40), respectively.

Days postpartum affected (P<0.05) estrous
response, conception rate, timed-AI pregnancy,
and synchronized pregnancy rates (Table 4).
Estrous response was greater (P<0.05) for long
(> 60 d) compared to short (< 40 d) and medium
(40 to 59 d) postpartum cows, which were
similar (P>0.05) to each other. Conception and
timed-AI pregnancy rates were greater (P<0.05)
for long compared to short postpartum cows, but
were similar (P>0.05) to medium postpartum
cows. Short postpartum cows had similar
(P>0.05) conception and timed-AI pregnancy
rates compared to medium postpartum cows.
Synchronized pregnancy rates were greater
(P<0.05) for long postpartum cows compared to
medium and short postpartum cows (P<0.05)
while the medium postpartum cows had greater
(P<0.05) synchronized pregnancy rates
compared to the short postpartum cows. Thirty-


day pregnancy rate was greater (P<0.05) for
long (94.5%) postpartum cows compared to
short (70.3%) and medium (76.9%) postpartum
cows, which were similar (P>0.05) to each
other. Body condition score did not (P>0.05)
affect estrous response, timed-AI pregnancy, or
synchronized pregnancy rates, but did affect
conception and 30-d pregnancy rates when
included as a covariate for the main and simple
treatment effects. Cows with a BCS > 5 (64.5%)
tended (P=0.10) to have a greater conception
rate compared to cows with a BCS < 5 (48.6%).
Cows with a BCS > 5 (84.3%) had a greater
(P<0.05) 30-d pregnancy rate compared to cows
with a BCS < 5 (68.6%). Cow age did not affect
(P>0.05) estrous response, conception rate,
timed-AI pregnancy, synchronized pregnancy,
or 30-d pregnancy rates when included as a
covariate for main and simple treatment effects.

In conclusion, synchronized pregnancy rates
were similar between cloprostenol sodium and
dinoprost tromethamine treatments in Select
Synch + CIDR protocols. The decreased estrous
response of the Select Synch + CIDR protocol
compromises the protocols overall effectiveness,
but synchronized pregnancy rates are improved
with addition of a timed-AI after 3 d of estrous
detection. The overall effectiveness of Select
Synch protocols are significantly influenced by
days postpartum at the start of treatment and
producers need to pay particular attention to
when synchronization protocols are
implemented in relation to calving in suckled
Bos indicus x Bos taurus cattle.


'Regina D. Esterman, Graduate Student; Brad R. Austin, Former Graduate Student; Steaven A. Woodall,
Former Graduate Student; Gary R. Hansen, Former Assistant Professor, UF-IFAS North Florida Research
and Education Center, Marianna, FL; Matt Hersom, Assistant Professor; UF-IFAS, Animal Sciences,
Gainesville, FL; Joel V. Yelich, Associate Professor, UF-IFAS Animal Sciences, Gainesville, FL


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Table 1. Main treatment effects for estrous response, conception rate, and synchronized pregnancy
rate of suckled Bos indicus x Bos taurus cows synchronized with controlled intravaginal progesterone-
releasing device (CIDR; new vs once-used) and prostaglandin Fz2 [(cloprostenol sodium (cloprostenol)
vs dinoprost tromethamine (dinoprost)] treatments (Experiment 1).a

Estrous Conception Synchronized
Variable response, % (n)b rate, % (n) pregnancy rate, % (n)d

Main effects

New CIDR 70.9(141) 45.0(100) 31.9(141)

Once-used CIDR 66.0 (141) 50.5 (93) 33.3 (141)

P-value P > 0.05 P > 0.05 P > 0.05


Cloprostenol 68.8 (141) 48.5 (97) 33.3 (141)

Dinoprost 68.1(141) 46.9 (96) 31.9(141)

P-value P > 0.05 P > 0.05 P > 0.05


aAll cows received GnRH (100 ftg) at the initiation of either a 7 d new or once-used CIDR. Cows
received either cloprostenol sodium (500 gg) or dinoprost tromethamine (25 mg) at CIDR removal.
Estrus was detected for 5 d and cows that exhibited estrus were inseminated 8 to 12 h later.
b Percentage of cows displaying estrus 5 d after prostaglandin Fz2 of total treated.
' Percentage of cows pregnant to AI of the total that exhibited estrus and were AI.
d Percentage of cows pregnant during the synchronized breeding of the total treated.


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Table 2. Effect of days postpartum (DPP) at the initiation of controlled intravaginal progesterone-
releasing device (CIDR) and prostaglandin Fz, treatments on estrous response, conception rate, and
synchronized pregnancy rates of suckled Bos indicus x Bos taurus cows (Experiment 1).'

Estrous Conception Synchronized pregnancy
DPP response, % (n)b rate, % (n) rate, % (n)d

<50 57.8 (109)e 27.0 (63)e 15.6 (109)

51-69 64.8 (91) 49.2 (59) 31.9 (91)

> 70 86.6 (82) f 64.8 (71)f 56.1 (82) g

a All cows received GnRH (100 |jg) at the initiation of either a 7 d new or once-used CIDR. Cows
received either cloprostenol sodium (500 gg) or dinoprost tromethamine (25 mg) at CIDR removal.
Estrus was detected for 5 d and cows that exhibited estrus were inseminated 8 to 12 h later.
b Percentage of cows displaying estrus 5 d after prostaglandin Fz2 of total treated.
' Percentage of cows pregnant to AI of the total that exhibited estrus and were AI.
d Percentage of cows pregnant during the synchronized breeding of the total treated.
e,f,g Means without a common superscript within a column differ (P<0.05)


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Table 3. Main treatment effects for estrous response, conception rate, timed-AI pregnancy rate, and
synchronized pregnancy rate of suckled Bos indicus x Bos taurus cows synchronized with controlled
intravaginal progesterone-releasing device (CIDR; new vs once-used) and prostaglandin Fz2
[(cloprostenol sodium (cloprostenol) vs dinoprost tromethamine (dinoprost)] treatments (Experiment
2).a

Estrous Timed-AI Synchronized
response, % Conception pregnancy pregnancy rate,
Variable (n)b rate, % (n)- rate, % (n)d % (n)

Main effects

New CIDR 51.2 (125) 67.2 (64) 32.8 (61) 50.4 (125)

Once-used CIDR 49.2 (130) 53.1 (64) 31.8 (66) 42.3 (130)

P-value P > 0.05 P = 0.10 P > 0.05 P > 0.05


Cloprostenol 53.5 (129) 59.4 (69) 28.3 (60) 45.0 (129)

Dinoprost 46.8 (126) 61.0 (59) 35.8 (67) 47.6 (126)

P-value P > 0.05 P > 0.05 P > 0.05 P > 0.05

aAll cows received GnRH (100 |jg) at the initiation of either a 7 d new or once-used CIDR. Cows
received either cloprostenol sodium (500 gg) or dinoprost tromethamine (25 mg) at CIDR removal.
Estrus was detected for 3 d and cows exhibiting estrus were AI 8 to 12 h later. Cows not displaying
estrus were timed-AI and received GnRH 76 to 80 h after prostaglandin F2a.
b Percentage of cows displaying estrus 5 d after prostaglandin F2z 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.


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Table 4. Effect of days postpartum (DPP) at the initiation of controlled intravaginal progesterone-
releasing device (CIDR) treatments and prostaglandin F2, treatments on estrous response, conception
rate, and pregnancy rates of suckled Bos indicus x Bos taurus cows (Experiment 2).a

Estrous Timed-AI Synchronized
Response, Conception pregnancy rate pregnancy
DPP % (n)b rate %, (n)- %, (n)d rate, % (n)e

< 40 39.2 (74) 44.8 (29) f 20.0 (45) 29.7 (74)

40-59 45.4 (108)' 57.1 (49) fg 33.9 (59) fg 44.4 (108)g

> 60 68.5 (73) g 72.0 (50) g 52.2 (23) g 65.8 (73) h

aAll cows received GnRH (100 |jg) at the initiation of either a 7 d new or once-used CIDR. Cows
received either cloprostenol sodium (500 gg) or dinoprost tromethamine (25 mg) at CIDR removal.
Estrus was detected for 3 d and cows exhibiting estrus were AI 8 to 12 h later. Cows not displaying
estrus were timed-AI and received GnRH 76 to 80 h after prostaglandin Fza.
b Percentage of cows displaying estrus 3 d after prostaglandin F2z 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,g,h Means without a common superscript within a column differ (P<0.05).


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100

90

80

70 63.6

60
c 50.0 48.9
50
5.
4 40
0 28.6
o 30 -

20 18.2

10

0
0 ---- -- ---- -- ---- -- ---- ------
48 60 72 84 96






Figure 1. Effect of interval from PGF2a to the onset of estrus on conception rates in suckled Bos
indicus x Bos taurus cows synchronized with controlled intravaginal progesterone-releasing device
(CIDR) and prostaglandin F2a treatments. Means between columns without a common letter differ
(P<0.05). Numbers in parenthesis indicate the number of cows inseminated within each category
(Experiment 1).


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Full Text

PAGE 1

Evaluation o f a New o r Once u sed CIDR a nd Two Different Prostaglandin F 2 Treatments to Synchronize Suckled Bos i ndicus Bos t aurus Cows Regina D. Esterman 1 Brad R. Austin Ste a ven A. Woodall Gary R. Hansen Matt Hersom Joel V. Yelich Summary Multiparous suckled Bos indicus Bos taurus cows were used in two experiments to evaluate the Select Synch and Select Synch + timed artificial insemination (TAI) synchronization protocols combined with a controlled intravaginal progesterone device (CIDR). Both experiments were conducted as 2 2 factorial designs with the main effects being CIDR type (new vs once-used) and PGF type (cloprostenol sodium vs dinoprost tromethamine). Cows in both experiments received GnRH and either a new CIDR or onceused CIDR on d 0, followed by CIDR removal and either cloprostenol sodium or dinoprost tromethamine on d 7. In Exp. 1, estrus was detected for 5 d following PGF and cows were AI 8 to 12 h after observed in estrus. In Exp. 2, estrus was detected for 3 d following PGF and cows were AI 8 to 12 h after observed in estrus. Cows not exhibiting estrus by 72 h after PGF were timed-AI between 76 to 80 h and received GnRH. In Exp. 1, estrous response, conception, and synchronized pregnancy rates were similar (P>0.05) for both new and once-used CIDR, as well as cloprostenol sodium and dinoprost tromethamine. Interval from PGF to onset of estrus influenced (P<0.05) conception rates. had greater (P<0.05) conception rates compared to In Exp. 2, estrous response, conception, timed-AI, and synchronized pregnancy rates were similar (P>0.05) for new and once-used CIDR, as well as cloprostenol sodium and dinoprost tromethamine. In both experiments, estrous response, conception, and pregnancy rates increased (P<0.05) as days from calving increased. In summary, CIDR (new vs onceused) and PGF (cloprostenol sodium vs dinoprost tromethamine) types resulted in similar responses when used in the Select Synch protocol and the response to synchronization treatment increased as days from calving increased in suckled Bos indicus Bos taurus cows. Introduction Estrous synchronization allows for more cows to display estrus and ovulate over a period of several days. This allows for either a reduction of daily estrous detection over a 21 d estrous cycle to 1 to 5 d, or elimination of estrous detection and insemination of all cows at a predetermined time known as timed-AI. 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 Suckled Bos indicus Bos taurus cows achieved similar pregnancy rates when synchronized with CIDR inserts and two PGF types. Greater synchronized pregnancy rates were observed with a 3 d estrous detection and clean up timed artificial insemination compared to a 5 d estrous detection following PGF Days from calving had a strong influence on response to synchronizatio n protocol.

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protocol is that some cattle express estrus several days before PGF which requires additional estrous detection. This problem can be eliminated with addition of a progestogen between the GnRH and PGF treatments. An added benefit of the progestogen is that it can induce estrous cycles in some anestrous cows. Limited research has been conducted using the GnRH + PGF protocols in Bos indicus Bos taurus cattle either with or without a progestogen and that research was met with limited success. The reason(s) for the less than acceptable results are unclear, but may be due to a decreased synchronized estrous response, which may be influenced by decreased luteolytic actions of PGF Several studies have reported similar responses in Bos taurus cattle synchronized with synchronization systems that compared cloprostenol sodium to dinoprost tromethamine, but limited work has been done in Bos indicus Bos taurus cows. The CIDR is an effective synchronization agent that induces estrus in some anestrous cattle. A new CIDR (1.9 g progesterone) maintains circulating progesterone concentrations > 1 ng/mL for at least 15 d after insertion, suggesting that a CIDR could be used for two consecutive 7 d treatments and still suppress estrus. Furthermore, autoclaving a once-used CIDR brings more progesterone to the surface making more available for absorption in the vagina, as well as decreasing the possibility of disease transmission. Re-use of the CIDR could help producers decrease the cost of synchronizing cattle, but it must be accomplished without a reduction in AI pregnancy rates. Evaluation of a once-used CIDR has not been conducted in suckled Bos indicus Bos taurus cows Therefore, the objectives of these experiments were to evaluate the effectiveness of a new CIDR compared to a once-used CIDR and cloprostenol sodium compared to dinoprost tromethamine in two GnRH + PGF synchronization protocols in suckled Bos indicus Bos taurus cows. Materials and Methods Two experiments were conducted from January to March during two successive years at the Bar L Ranch in Marianna, FL. In Experiment 1, multiparous, suckled Bos indicus Bos taurus cows (n = 284) were used. Mean ( SD) cow age was 5.7 1.9 yr, days postpartum (DPP) was 58.0 12.5 d, body weight (BW) was 1098 106 lbs, and body condition score was 5.2 0.5 (BCS: 1 = emaciated, 9 = obese). The percentage of Bos indicus breeding ranged from approximately 10 to 38% with the remainder being Bos taurus breeding. The experiment was a 2 2 factorial design. At the start of the experiment (d 0), cows were equally distributed by DPP and cow age to one of two progesterone treatments, which included a new CIDR (1.38 g; Eazi, Pfizer Animal Health) and a once-used CIDR (new CIDR used once and autoclaved before the second use). All cows received GnRH (100 g i.m.; Fertagyl Intervet) at CIDR insertion and BCS were recorded. On d 7, CIDR were removed and cows within each CIDR treatment were equally distributed by DPP, BCS, and cow age to receive either cloprostenol sodium (cloprostenol; 500 g i.m.; Estrumate Schering-Plough Veterinary Corp.) or dinoprost tromethamine (dinoprost; 25 mg i.m.; Prostamate Agrilabs). CIDR removal to aid in estrous detection. Estrus was visually detected three times daily at 0700, 1200, and 1700 h for 5 d following PGF Estrus was defined as a cow standing to be mounted by another cow and/or a half to full red observed in estrus. Frozen-thawed semen from a single sire of known fertility was used and cows were inseminated by two AI technicians. Seven d after the last cow was inseminated, bulls were placed with cows. Pregnancy was diagnosed approximately 55 d after AI using a real-time B-mode ultrasonography machine

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(Aloka 500V, Corometrics Medical Systems) with a 5.0 MHz transducer. Because there was a 7-d period where cows were neither inseminated nor exposed to bulls, differences in fetal size were used to determine whether a pregnancy resulted from the synchronized breeding or clean-up bull. In Experiment 2, multiparous suckled Bos indicus Bos taurus cows (n = 259) were used. Mean ( SD) cow age was 6.9 1.9 yr, DPP was 48.5 12.8 d, and BCS was 5.1 0.5. The experiment was a 2 2 factorial design and animals were assigned to the same synchronization treatments as Experiment 1. Estrus was detected for 72 h following PGF as described in Experiment 1. Cows were AI 8 to 12 h after observed in estrus. All cows that had not displayed estrus by 73 h after PGF were timed-AI and received GnRH between 76 and 80 h after PGF Cows were inseminated by a single AI technician with frozen-thawed semen from five sires that were pre-assigned to cows before AI by the co-operating producer. Seven days after the last cow was inseminated, bulls were placed with cows and pregnancy was diagnosed as described in Experiment 1. The GENMOD procedure of SAS (SAS Inst. Inc.) was used for the statistical analysis. The main effects of CIDR and PGF treatments, and CIDR PGF were evaluated for estrous response, conception, 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 wer e treated as independent variables. Results In Experiment 1, estrous response, conception rate, and synchronized pregnancy rates were similar ( P >0.05) for main effects of CIDR and PGF treatments, as well as the simple treatment effects (Table 1). Thirty-day pregnancy rates were similar ( P >0.05) for the new (78.0%) compared to the once-used (79.4%) CIDR treatment and for the cloprostenol (77.3%) compared to the dinoprost (80.1%) treatment. Days post partum effected ( P <0.05) estrous response, conception, and synchronized pregnancy rates (Table 2). Cows that were long P <0.05) estrous response compared to cows that were postpartum, which were similar ( P >0.05). Conception rates were similar ( P >0.05) for cows that were medium and long postpartum, both of which were greater ( P <0.05) compared to short postpartum cows. Synchronized pregnancy rates were greater ( P <0.05) for cows that were long postpartum compared to short and mediu m postpartum cows, which were different ( P <0.05) from each other. Thirty-day pregnancy rates were greater ( P <0.05) for cows that were medium (79.1%) and long (87.8%) postpartum compared to cows that were short (71.6%) postpartum. Cows that were medium and short postpartum had similar ( P >0.05) thirty-day pregnancy rates. No cows were detected in estrus until 48 h after PGF 2 for any of the four treatments. The mean interval from PGF 2 to onset of estrus (64.4 16.0 h) was not influenced ( P >0.05) by main or simple treatment effects. Interestingly, there was an effect ( P < 0.01) of interval from PGF to onset of estrus on conception rate (Figure 1). Cows which displayed estrus 48, 60, 72, and 84 h after PGF had similar ( P >0.05) conception rates, but cows which displayed estrus at 48, 60, and 72 h had greater ( P <0.05) conception rates compared to cows that displayed estrus 96 h after PGF Cows that displayed estrus at 84 h had similar ( P >0.05) conception rates compared to cows which displayed estrus at 96 h. Cow age and BCS did not affect ( P >0.05) estrous response, conception rate, synchronized pregnancy, or 30-d pregnancy rates when included as covariates for main and simple treatment effects. In Experiment 2, estrous response, conception ra te, timed-AI pregnancy, and synchronized pregnancy rates were similar ( P >0.05) for main

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effects of CIDR and PGF treatments (Table 3). Thirty-day pregnancy rates were similar ( P >0.05) for the new (83.2%) compared to the once-used (76.9%) CIDR treatment and for the cloprostenol (76.7%) compared to the dinoprost (83.3%) treatment. The CIDR treatment tended ( P =0.10) to influence conception rate as 14.1% more cows that received a new CIDR became pregnant compared to cows that received a once-used CIDR (Table 3). The interval from PGF to onset of estrus was not ( P>0.05) affected by treatment, with a mean interval of 58.6 10.3 h across the four treatments. Interval from PGF to onset of estrus did not ( P >0.05) effect conception rates. Conception rates for cows that exhibited estrus 48, 60 and 72 h after PGF were 61.8 (n=55), 57.6 (n=33), and 60.0% (n=40), respectively. Days postpartum affected ( P <0.05) estrous response, conception rate, timed-AI pregnancy, and synchronized pregnancy rates (Table 4). Estrous response was greater ( P <0.05) for long (40 to 59 d) postpartum cows, which were similar ( P >0.05) to each other. Conception and timed-AI pregnancy rates were greater ( P <0.05) for long compared to short postpartum cows, but were similar ( P >0.05) to medium postpartum cows. Short postpartum cows had similar ( P >0.05) conception and timed-AI pregnancy rates compared to medium postpartum cows. Synchronized pregnancy rates were greater ( P <0.05) for long postpartum cows compared to medium and short postpartum cows ( P <0.05) while the medium postpartum cows had greater ( P <0.05) synchronized pregnancy rates compared to the short postpartum cows. Thirtyday pregnancy rate was greater ( P <0.05) for long (94.5%) postpartum cows compared to short (70.3%) and medium (76.9%) postpartum cows, which were similar ( P >0.05) to each other. Body condition score did not ( P >0.05) affect estrous response, timed-AI pregnancy, or synchronized pregnancy rates, but did affect conception and 30-d pregnancy rates when included as a covariate for the main and simple tre tended ( P =0.10) to have a greater conception rate compared to cows with a BCS < 5 (48.6%). ( P<0.05) 30-d pregnancy rate compared to cows with a BCS < 5 (68.6%). Cow age did not affect ( P>0.05) estrous response, conception rate, timed-AI pregnancy, synchronized pregnancy, or 30-d pregnancy rates when included as a covariate for main and simple treatment effects. In conclusion, synchronized pregnancy rates were similar between cloprostenol sodium and dinoprost tromethamine treatments in Select Synch + CIDR protocols. The decreased estrous response of the Select Synch + CIDR protocol compromises the protocols overall effectiveness, but synchronized pregnancy rates are improved with addition of a timed-AI after 3 d of estrous detection. The overall effectiveness of Select Synch protocols are significantly influenced by days postpartum at the start of treatment and producers need to pay particular attention to when synchronization protocols are implemented in relation to calving in suckled Bos indicus Bos taurus cattle. 1 Regina D. Esterman Graduate Student; Brad R. Austin Former Graduate Student ; Ste a ven A. Woodall Former Graduate Student; Gary R. Hansen, Former Assistant Professor, UF IFAS North Florida Research and Education Center, Marianna, FL; Matt Hersom Assistant Professor; UF IFAS, Animal Sciences Gainesville, FL; Joel V. Yelich Associate Professor, UF IFAS Animal Sciences, Gainesville, FL

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Table 1. Main treatment effects for e strous response, conception rate, and synchronized pregnancy rate of suckled Bos indicus Bos taurus cows synchronized with controlled intravaginal progesterone releasing device (CIDR; new vs once used) and prostaglandin F 2 [(cloprostenol sodium (cloprostenol) vs dinoprost tromethamine (dinoprost)] treatments (Experiment 1). a Variable Estrous response, % (n) b Conception rate, % (n) c Synchronized pregnancy rate, % (n) d Main effects New CIDR 70.9 (141) 45.0 (100) 31.9 (141) Once used CIDR 66.0 (141) 50.5 (93) 33.3 (141) P value P > 0.05 P > 0.05 P > 0.05 Cloprostenol 68.8 (141) 48.5 (97) 33.3 (141) Dinoprost 68.1 (141) 46.9 (96) 31.9 (141) P value P > 0.05 P > 0.05 P > 0.05 a All cows received GnRH (100 g) at the initiation of either a 7 d new or once used CIDR. Cows tromethamine (25 mg) at CIDR removal. Estrus was detected for 5 d and cows that exhibited estrus were inseminated 8 to 12 h later. b Percentage of cows displaying estrus 5 d after prostaglandin F 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 during the synchronized breeding of the total treated.

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Table 2. Effect of days postpartum (DPP) at the initiation of controlled intravaginal progesterone releasing device (CIDR) and prostaglandin F 2 treatments on e strous response, conception rate, and synchronized pregnancy rates of suckled Bos indicus Bos taurus cows (Experiment 1). a DPP Estrous response, % (n) b Conception rate, % (n) c Synchronized pregnancy rate, % (n) d 57.8 (109) e 27.0 (63) e 15.6 (109) e 51 69 64.8 (91) e 49.2 (59) f 31.9 (91) f 86.6 (82) f 64.8 (71) f 56.1 (82) g a All cows received GnRH (100 g) at the initiation of either a 7 d new or once used CIDR. Cows Estrus was detected for 5 d and cows that exhibited estrus were inseminated 8 to 12 h later. b Percentage of cows displaying estrus 5 d after prostaglandin F 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 during the synchronized breeding of the total treated. e,f,g Means without a common superscript within a column differ (P<0.05)

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Table 3. Main treatment effects for e strous response, conception rate, timed AI pregnancy rate, and synchronized pregnancy rate of suckled Bos indicus Bos taurus cows synchronized with controlled intravaginal progesterone releasing device (CIDR; new vs once used) and prostaglandin F 2 [(cloprostenol sodium (cloprostenol) vs dinoprost tromethamine (dinoprost)] treatments (Experiment 2). a Variable Estrous response % (n) b Conception rate, % (n) c Timed AI pregnancy rate, % (n) d Synchronized pregnancy rate, % (n) e Main effects New CIDR 51.2 (125) 67.2 (64) 32.8 (61) 50.4 (125) Once used CIDR 49.2 (130) 53.1 (64) 31.8 (66) 42.3 (130) P value P > 0.05 P = 0.10 P > 0.05 P > 0.05 Cloprostenol 53.5 (129) 59.4 (69) 28.3 (60) 45.0 (129) Dinoprost 46.8 (126) 61.0 (59) 35.8 (67) 47.6 (126) P value P > 0.05 P > 0.05 P > 0.05 P > 0.05 a All cows received GnRH (100 g) at the initiation of either a 7 d new or once used CIDR. Cows Estrus was detected for 3 d and cows exhibiting estrus were AI 8 to 12 h later. Cows not d isplaying estrus were timed AI and received GnRH 76 to 80 h after prostaglandin F 2 b Percentage of cows displaying estrus 5 d after prostaglandin F 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 4 Effect of days postpartum (DPP) at the initiation of controlled intravagin al progesterone releasing device (CIDR) treatments and prostaglandin F 2 treatments on e strous response, conception rate, and pregnancy rates of suckled Bos indicus Bos taurus cows (Experiment 2). a DPP Estrous Response, % (n) b Conception rate %, (n) c Timed AI pregnancy rate %, (n) d Synchronized pregnancy rate, % (n) e < 40 39.2 (74) f 44.8 (29) f 20.0 (45) f 29.7 (74) f 40 59 45.4 (108) f 57.1 (49) f,g 33.9 (59) f,g 44.4 (108) g 68.5 (73) g 72.0 (50) g 52.2 (23) g 65.8 (73) h a All cows received GnRH (100 g) at the initiation of either a 7 d new or once used CIDR. Cows Estrus was detected for 3 d and cows exhibiting estrus were AI 8 to 12 h later. Cows not displaying estrus were timed AI and received GnRH 76 to 80 h after prostaglandin F 2 b Percentage of cows displaying estrus 3 d after prostaglandin F 2 of total treated. c Percentage of cows pregnant to AI of the total that exhibi ted 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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50.0 63.6 48.9 28.6 18.2 0 10 20 30 40 50 60 70 80 90 100 48 60 72 84 96 Conception rate, % Figure 1. Effect of interval from PGF to the onset of estrus on conception rates in suckled Bos indicus Bos taurus cows synchronized with controlled intravaginal progesterone releasing device (CIDR) and prostaglandin F 2 treatments. Means between columns without a common letter differ (P<0.05). Numbers in parenthesis indicate the number of cows inseminated within each category (Experiment 1).