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TERMINATION OF EARLY PREGNANCY IN EWES BY USE OF A PROSTAGLANDIN ANALOGUE AND SUBSEQUENT FERTILITY
Author(s) -
Tyrrell R. N.,
Lane J. G.,
Nancarrow C. D.,
Connell P. J.
Publication year - 1981
Publication title -
australian veterinary journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.382
H-Index - 59
eISSN - 1751-0813
pISSN - 0005-0423
DOI - 10.1111/j.1751-0813.1981.tb00450.x
Subject(s) - estrous cycle , pregnancy , cloprostenol , luteolysis , fertility , prostaglandin analogue , prostaglandin , zoology , endocrinology , medicine , biology , corpus luteum , andrology , ovulation , population , environmental health , genetics
SUMMARY Of 87 Dorset ewes injected at 20 to 60 days of pregnancy with either 125 μg or 250 μg of the prostaglandin F 2α 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 < 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.