Factors Affecting Bovine Ovarian Activity after Parturition

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Abstract
A total of 250 dairy cows were divided, after normal parturitions, into three production groups: under 22 kg. per day, 22 to 30 kg. and over 30 kg. per day to determine the influence of production for 120 days after parturition on reproductive performance. The cows were observed for estrus twice daily. Rectal palpations were performed twice weekly beginning 3 to 5 days after the cow calved and continued until she was diagnosed pregnant. Size and condition of uterine horns and size and position of ovarian structures were recorded. Average days from parturition to first ovulation and first estrus for the three production groups were: low, 13.1 and 28.4; medium, 14.0 and 33.1; high, 15.5 and 36.9. Difference between low and high producers was significant. Percent of cows in each of the three groups'that formed follicular cysts was 7.0, 9.9 and 22.6 respectively. Only three of 29 cows with follicular cysts were observed in estrus. A majority of cysts occurred during the first two estrous cycles, constituting the most important factor correlated with lengthening intervals from parturition to first ovulation, estrus, and conception. Cystic corpora lutea did not vary between estrous cycles and did not affect cycle length. Over 90% of first ovulations before 15 days after parturition occurred from the ovary opposite the previously gravid horn. Sixty percent of ovulations between 15 and 20 days occurred in the ovary opposite the gravid horn. Subsequent to regression of the previously gravid horn to 60 mm. diameter, frequency of first ovulations from each ovary was normal. Copyright © 1968. American Society of Animal Science . Copyright 1968 by American Society of Animal Science

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