Oestrus synchronization and fertility in heifers treated with prostaglandin F2alpha

Oestrus was synchronized with prostaglandin F2alpha in Tham salt buffer (25 mg. and 12.5 mg.) injected intramuscularly on two consecutive days in 41 Dutch Friesian heifers. Thirty-five animals (85,3%) showed heat within 2-5 days of the start of treatment. Degree of synchronization was low if PGF 2alpha was injected before D5. Conception rate was low (31,4%) in the synchronized oestrus, but was normal (58%) at the post-synchronized oestrus. Based on observation for oestrus and rectal palpation of ovaries at 8 hourly intervals, oestrus occurred over a period of 62,1 +/- 3,0 hours and ovulation occurred 29,8 +/- 1,4 hours after the onset of oestrus. The average time from first treatment to ovulation was 93,0 +/- 18,8 hours. The length of the synchronized oestrus was significantly longer (P less than 0,05) than the pretreatment oestrus.