Reproductive response of progestogen-treated sheep in confinement to a single and double insemination.

The reproductive responses to one and two inseminations of fresh extended semen were compared in crossbred sheep housed in confinement. In three trials, ewes in progestogen-induced estrus were inseminated 54 to 56 h after sponge removal. Half the ewes received a second insemination 4 or 5 h later. Resultant fertility, litter size and embryonic mortality indicated no advantage to a double insemination. Conception rates to one and two inseminations according to d 18 plasma progesterone levels were 66 and 63%, 85 and 86% and 74 and 80% in trials 1, 2 and 3, respectively. Corresponding lambing rates were 55 and 56%, 73 and 69% and 67 and 76%. Mean litter sizes were 2.1 and 2.5, while embryonic mortality after the first 2 wk of pregnancy was estimated at 13% for both groups. Single inseminations therefore simplify artificial insemination and double the number of ewes that can be inseminated/ejaculate.