title: Termination of early pregnancy in ewes by use of a prostaglandin analogue and subsequent fertility.
abstract: Of 87 Dorset ewes injected at 20 to 60 days of pregnancy with either 125 micrograms or 250 micrograms of the prostaglandin F2 alpha analogue, cloprostenol, 72 (83%) were detected in oestrus by teaser rams within 7 days. A total of 60 ewes mated with fertile rams 14 to 28 days after treatment and 36 of these (60%) subsequently lambed. Thirty-eight ewes mated with fertile rams 29 to 56 days after treatment and 30 of these (79%) subsequently lambed. The difference in fertility between the 2 periods was not significant. Six additional ewes which did not respond to the cloprostenol lambed normally within 6 weeks. They were more than 100 days pregnant when treated. In ewes which first exhibited oestrus by 7 days of treatment, plasma progesterone concentrations fell from near 4 ng/ml to 0.6 ng/ml within 48 h of treatment. In ewes not detected in oestrus progesterone concentrations did not decrease to similar low levels (1.4 ng/ml; t-test p less than 0.005). Concentrations in the 6 ewes treated near 100 days of pregnancy dropped from 7.4 to 4.4 ng/ml over 48 h. Overall, the progesterone concentrations indicated that 92% of ewes treated at 20 to 60 days of pregnancy experienced rapid luteolysis in response to the cloprostenol. There were no differences between the 2 doses of cloprostenol in the responses or subsequent fertility of the ewes.
mesh_terms: D000019:Abortifacient Agents / Q000494:pharmacology; D000020:Abortifacient Agents, Nonsteroidal / Q000494:pharmacology; D000028:Abortion, Induced / Q000662:veterinary*; D000818:Animals; D003008:Cloprostenol / Q000494:pharmacology; D004971:Estrus; D005260:Female; D005298:Fertility / Q000187:drug effects*; D011247:Pregnancy; D011374:Progesterone / Q000097:blood; D011461:Prostaglandins F, Synthetic / Q000494:pharmacology; D012756:Sheep / Q000502:physiology*
chemical_list: D000019:Abortifacient Agents; D000020:Abortifacient Agents, Nonsteroidal; D011461:Prostaglandins F, Synthetic; D003008:Cloprostenol; D011374:Progesterone