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Research
1.
Effect of estrus-AI interval on timed AI pregnancy
rates in beef cows inseminated with fresh extended
or frozen thawed semen -
R. K. Kasimanickam, W. D. Whittier
Vet World. 2011; 4(6): 245-247
doi: 10.5455/vetworld.4.245
Abstract
We hypothesize that insemination with fresh extended
semen will improve the AI pregnancy rate due to its
prolonged longevity in female reproductive tract
compared to frozen thawed semen. The objective of
this trial was to determine the effect of fresh and
frozen semen on fixed-time AI pregnancy rate in beef
cows synchronized with progesterone based CO-Synch
protocols and inseminated at different estrus-AI
intervals. Angus cross beef cows (N=180) were
synchronized with CO-Synch-CIDR protocols for a
fixed-time AI. A subset of cows (N=110) received
Heatwatch estrus detection system's pressure sensor
at CIDR removal to determine the time of estrus.
Cows were divided into two groups, inseminated
either at 47h (early) or at 67h (late) from CIDR
removal with fresh extended (3 million sperm) or of
frozen thawed (20 million sperm) semen. Results
indicated that cows inseminated at 67 h had
numerically higher fixed time AI pregnancy compared
to cows inseminated at 47 h [44.4% (40/90) vs. 33.3%
(30/90); P=0.13]. Cows inseminated with frozen
thawed semen had similar fixed time AI pregnancy
compared to fresh extended semen [40.8 (31/76) vs.
37.5% (39/104); P=0.66]. AI-estrus interval was
divided into three groups < 0 h (AI occurred before
estrus), 0 to 16 h and > 16 h (AI occurred 16 h
after estrus). The AI pregnancy rates for fresh
semen for the 3 estrus-AI intervals were similar to
frozen semen. In conclusion, the fresh semen yielded
similar AI pregnancy as frozen semen when
inseminated at different estrus-AI interval in a
fixed time AI breeding program in beef cows.
Keywords: Estrus, Artificial Insemination,
Synchronization of estrus, Pregnancy, Frozen Semen,
Thawed Semen.
