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Postpartum estrus and serum levels of progesterone and estradiol-17β were investigated in fourteen beef cows. Calves were weaned at 3 days of age. All cows were given 1 kg of concentrate daily, and they were placed on pasture in summer and were fed hay ad libitum in winter season. Observations for estrus were made twice daily. Ovaries were examined by rectal palpation at 2-day intervals beginning on 7 days postpartum. Blood was collected from a jugular vein twice a weak from one month before to three months after parturition. Serum progesterone and estradiol-17β concentration were determined by radioimmunoassay. The cows were bred at the estrus after 40 days postpartum.<BR>The cows slightly gained body weight during three months following calving. Although first postpartum ovulation occurred at 12.4 days, it was not accompanied by estrus in 9 of 14 cows. All cows except one exhibited estrus at the second ovulation, with an average of 24.0 days of first postpartum estrus. The interval from the first to the second ovulation was shorter than the second cycle (17.6 vs. 21.6 days, P <.05), particularly in cows which did not exhibit estrous behaviour at the first postpartum ovulation. It was suggested from the rectal examination and serum progesterone concentration that some of corpora lutea formed following the first ovulation might not have full function.<BR>Serum progesterone peak after the first ovulation was lower than the peak after the second ovulation (2.55 vs. 5.16 ng/m<I>l</I>, P <.01). Serum estradio1-17β concentration varied from 5 to 20 pg/m<I>l</I> following parturition. Twice weekly blood collection, however, failed to show whether there was a difference in serum estradio1-17β concentration between quiet ovulation and estrus. The average interval from calving to conception and number of inseminations required for conception were 71.9 days and 1.6 times.
- 日本繁殖生物学会の論文
日本繁殖生物学会 | 論文
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