Treatment with progesterone impregnated controlled internal drug releasers (CIDR) in early pregnancy can increase ewe reproductive performance. Return mating patterns, pregnancy rates and multiple pregnancies were evaluated in supplemented ewes and hoggets. Supplementation was over the 5 d from day 7 to 9 until day 12 to 14 post-mating. Supplementation had no effect on the pattern and incidence of return matings in ewes. In contrast, supplemented hoggets tended to return later with less returning (18% v 35%). Supplementation had no effect on ewe pregnancy rate although more supplemented hoggets lambed to first service (79% v 56%, P<0.05). Supplementation increased multiple pregnancies resulting in 23% more foetuses in ewes and 40% more in hoggets. The progesterone supplemented sheep may be a useful experimental model for studies in reproductive wastage.
Proceedings of the New Zealand Society of Animal Production, Volume 47, , 131-134, 1987
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