Effect on pregnancy rate of nonestrus insemination in previously inseminated dairy cows.
Lactating dairy cows (n = 157) designated for slaughter under the 1986 U.S. Dairy Termination Program were utilized in two trials to determine the effects of a second insemination on fertility. Cows that had been previously inseminated at estrus were inseminated again at 12-24 d later, when not in estrus. Cows that were reinseminated into the uterine body had significantly lower pregnancy rates (4% vs 40.6% for controls). Differences in pregnancy rates when the reinsemination was performed in the mid-cervical region were not significant (34.8% vs 50% for controls). Based upon these studies, intrauterine insemination of cows displaying questionable signs of estrus should be avoided in previously inseminated cows.
Weaver
L D
LD
Veterinary Medicine Teaching and Research Center University of California, Davis 18830 Road 112 Tulare, California 93274 USA.
Daley
C A
CA
Borelli
C L
CL