Wright J M, Kiracofe G H
Department of Animal Sciences and Industry Kansas State University, Manhattan, KS 66506 USA.
Theriogenology. 1988 Feb;29(2):497-504. doi: 10.1016/0093-691x(88)90251-8.
Estrous cycles were observed and concentrations of progesterone were measured after abortion in crossbred Angus heifers that were injected with a prostaglandin F(2) alpha analogue about day 50 (15 heifers), 75 (14 heifers), 100 (13 heifers) or 125 (49 heifers) of gestation. The average interval from injection to first estrus was 3.6, 4.2, 3.7 and 6.4 d for heifers injected at an average of 50, 75, 100 or 125 d of gestation, respectively. Cycles of fewer than 13 d were classified as short, those of 13 to 16 d as intermediate, those of 16 to 24 d as normal, and those of more than 24 d as long. Heifers aborted at 50 d of gestation had seven short and eight normal first cycles; heifers aborted at 75 d had 11 short cycles, two normal cycles, and one long cycle; heifers aborted at 100 d had 12 short cycles and one normal cycle; whereas heifers aborted at 125 d had 25 short cycles, 13 normal cycles, two long cycles, six intermediate cycles. Three heifers failed to exhibit a second estrus by 50 d after abortion. Of those heifers having short first cycles, short second cycles occurred in one of seven heifers aborted at Day 50, three of 11 at Day 75, seven of 12 at Day 100 and 18 of 25 at Day 125. Serum progesterone was measured at 0, 1 and 2 d after injection and at 5 and 10 d after the first estrus. Concentration of progesterone in serum declined before estrus, then increased by 5 d after estrus in all cases. Progesterone concentration increased between 5 and 10 d after estrus in heifers exhibiting normal estrous cycles but docreased in heifers having short cycles. Data indicate that the percentage of heifers having single or repeated short cycles after abortion increases as the duration of gestation increases to 100 d.
对妊娠约50天（15头小母牛）、75天（14头小母牛）、100天（13头小母牛）或125天（49头小母牛）的杂交安格斯小母牛注射前列腺素F(2)α类似物后，观察其发情周期并测量孕酮浓度。分别在平均妊娠50、75、100或125天注射的小母牛，从注射到首次发情的平均间隔时间分别为3.6、4.2、3.7和6.4天。少于13天的周期被归类为短周期，13至16天的为中间周期，16至24天的为正常周期，超过24天的为长周期。妊娠50天流产的小母牛首次发情周期有7个短周期和8个正常周期；妊娠75天流产的小母牛有11个短周期、2个正常周期和1个长周期；妊娠100天流产的小母牛有12个短周期和1个正常周期；而妊娠125天流产的小母牛有25个短周期、13个正常周期、2个长周期、6个中间周期。3头小母牛在流产后50天内未出现第二次发情。在首次发情周期短的小母牛中，妊娠50天流产的7头小母牛中有1头第二次发情周期短，妊娠75天流产的11头中有3头，妊娠100天流产的12头中有7头，妊娠125天流产的25头中有18头。在注射后0、1和2天以及首次发情后5和10天测量血清孕酮。所有情况下，血清孕酮浓度在发情前下降，然后在发情后5天升高。在表现出正常发情周期的小母牛中，发情后5至10天孕酮浓度升高，但在发情周期短的小母牛中则下降。数据表明，随着妊娠期延长至100天，流产后出现单次或重复短周期的小母牛百分比增加。
