Effects of Various Mating Stimuli on the LH Surge and Ovulation Time following Synchronization of Estrus in the Bovine

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Abstract
ESTRUS was synchronized in 39 cows by feeding 180 mg medroxyprogesterone acetate (MAP)/head/day for 11 days and injecting 5 mg estradiol benzoate on day 2 of MAP feeding. At the postsynchronization estrus, the cows were assigned to five groups differing in intensity of experimentally administered mating stimulation. Cows in Groups I, II, III and IV were maintained in a lot with estrogenized cows and observed constantly to detect first standing estrus. Group V cows were maintained with an epididymectomized bull and observed constantly for first standing estrus; they were allowed a single service by the bull. At detection of standing estrus, cows were removed from the lots and were given the appropriate mating stimuli. Cows in Group I received no further stimulus, cows in. Group II received artificial insemination with no clitoral stimulation, cows in Group III received artificial insemination with 10 sec. of manual stimulation of the clitoris; cows in Group IV were immediately bred three times in succession by a bull and cows in Group V received no further stimulation. Blood samples were collected hourly for 24 hr. from the onset of estrus and at 2-hr. intervals thereafter until ovulation was detected by rectal palpation. Serum LH was determined using double antibody radio-immunoassay. The LH surge was 4.5 hr. earlier in relation to the beginning of estrus (P<.10) in Group II than in Group I and ovulation time was 4.3 hr. earlier in relation to the beginning of estrus (P<.005) in Groups III, IV and V (greater stimulation) compared to Groups I and II (lesser stimulation). In this study, cervical stimulation tended to hasten the LH surge and clitoral stimulation hastened ovulation. Copyright © 1973. American Society of Animal Science . Copyright 1973 by American Society of Animal Science.

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