Vaca L A, Galina C S, Fernández-Baca S, Escobar F J, Ramírez B
Vet Rec. 1985 Oct 26;117(17):434-7. doi: 10.1136/vr.117.17.434.
The length of the oestrous cycle, oestrus and the time of ovulation were assessed in 20 adult, non-lactating zebu cows over 53 consecutive days of observation. Oestrus was detected at 30-minute observation periods daily. Peripheral blood samples were collected twice weekly for progesterone determination. To measure the length of the synchronised oestrous period, 10 cows with a palpable corpus luteum were injected with prostaglandin F2 alpha and continuously observed for 96 hours. Two cows at a time were exposed to a bull with a deviated penis for five minutes every three hours during this period. To measure the length of the natural oestrus, eight of the 10 cows from the previous experiment were continuously observed from day 21 after prostaglandin injection. They were kept during the daytime in a field with two teaser bulls and at night in a cattle pen where they were exposed to a teaser bull every three hours. Oestrus was considered to occur when the cow stood to be mounted. Ovulation was detected by rectal palpation every three hours in five cows starting six hours after receptivity commenced until ovulation took place. The length of the oestrous cycle was 20.1 +/- 1.9 days; 20 per cent of the animals did not show oestrus although their progesterone levels demonstrated that they were cycling. Two cows showed oestrus following prostaglandin F2 alpha injection although they were cycling as revealed by serum progesterone. Five animals showed behavioural oestrus around 118 hours after injection and following their release. Oestrus duration was 15.3 +/- 6.0 hours and ovulation occurred 28.2 +/- 5.0 hours after the start of the period of sexual receptivity.
在连续53天的观察期内，对20头成年、非泌乳的瘤牛进行发情周期、发情期和排卵时间的评估。每天以30分钟的观察时段来检测发情情况。每周采集两次外周血样本以测定孕酮水平。为了测量同步发情期的时长，对10头可摸到黄体的母牛注射前列腺素F2α，并持续观察96小时。在此期间，每3小时让两头母牛与一头阴茎弯曲的公牛接触5分钟。为了测量自然发情期的时长，对前一实验中的10头母牛中的8头，在注射前列腺素后的第21天开始进行连续观察。白天将它们饲养在有两头试情公牛的牧场中，晚上则关在牛栏里，每3小时让它们接触一头试情公牛。当母牛站立接受爬跨时即认为发情发生。对5头母牛，从接受交配开始6小时后直至排卵，每3小时通过直肠触诊检测排卵情况。发情周期的时长为20.1±1.9天；20%的动物虽孕酮水平表明其处于发情周期中，但未表现出发情。有两头母牛在注射前列腺素F2α后出现发情，尽管血清孕酮显示它们处于发情周期中。5头动物在注射及放归后约118小时出现行为发情。发情持续时间为15.3±6.0小时，排卵发生在性接受期开始后的28.2±5.0小时。
