A note on the effect of vasectomised rams and short-term exposures to entire rams prior to the breeding period on the reproductive performance of ewe lambs

The aim of this study was to determine the effects of either a 17-day exposure to vasectomised rams or a short-term exposure to entire rams on ewe lamb reproductive performance. Seven hundred and twenty-one Romney ewe lambs, 7–9 months of age, were randomly assigned to one of four treatment groups. Treatments included exposure to vasectomised rams for 17 days prior to breeding, exposure to entire rams for 4 or 2 days prior to breeding or not being exposed to either vasectomised or entire rams. Unteased ewe lambs and those exposed to entire rams for either 2 and 4 days were less (P < 0.05) likely to be mated in the first 17 days of breeding only and pregnant in the first 17 days of breeding compared to ewe lambs exposed to vasectomised rams for a full 17 days pre-breeding. Ewe lambs exposed to entire rams for 2 days were more (P < 0.05) likely to be mated in the first 8 days of breeding, mated in the first 17 days of breeding only and pregnant in the first 17 days of breeding compared to unteased ewe lambs. Therefore, a short-term exposure to entire rams can be used to induce breeding activity in ewe lambs, although it is not as effective as a full 17-day exposure to vasectomised rams.