Estrus in relation to time of administration of prostaglandin F2alpha to heifers.
Holstein heifers (95) were given two injections of prostaglandin F2alpha, the first on day 0 and the second either at 0600 h or 1800 h on day 12. Interval from the second treatment to first observation of estrus did not differ between heifers treated during the morning (69.8 +/- 4.4 h) or evening (72.7 +/- 5.2 h). However, estrus was detected sooner after treatment of heifers during July 1975 (49 +/- 2 h) than after treatment during June 1976 (85 +/- 8 h). Estrus began at 64 +/- 5, 73 +/- 7, and 76 +/- 7 after the second injection during August 1975, October 1976, and December 1975. Heifers treated during the morning in October were detected in estrus sooner (57 +/- 3 versus 95 +/- 13 h) than those treated during the evening. An interaction of season by time may affect interval from prostaglandin F2alpha treatment to onset of estrus.
D000818:Animals; D002417:Cattle / Q000502:physiology*; D004971:Estrus / Q000187:drug effects*; D005260:Female; D011247:Pregnancy; D011460:Prostaglandins F / Q000494:pharmacology*; D012621:Seasons; D013997:Time Factors
D011460:Prostaglandins F