Responses of tranquilized post-partum ewes to alien lambs

Abstract

The objective of this study was to determine the effect of tranquilization on the responses of ewes to alien lambs substituted for own lambs 48–72 h after parturition. Eleven ewes whose young had been taken away, and nine ewes with a lamb of their own, were penned with alien lambs following a single injection of the tranquilizer perphenazine. Seventeen control ewes, including 15 whose only young had been taken away, were also exposed to alien lambs after receiving placebo injections of normal saline. The responses of the ewes to the alien lambs were studied over a four-day period. All ten tranquilized ewes exposed to a single alien lamb without their own young present readily accepted the strange offspring. All of the tranquilized ewes accompanied by one of their own offspring, and a single ewe that was given an alien set of twins in place of her own single lamb, subsequently rejected the strange young. Six of 15 control ewes, with own young removed, accepted alien lambs. The remaining 11 control ewes rejected alien lambs. The success of fostering appeared to be positively related to the persistence of sucking attempts by the lamb, and inversely related to the aggressiveness of the ewe. Tranquilization under the conditions employed can be an efficient technique for fostering single alien lambs on post-partum ewes that have lost their own lambs, but does not facilitate fostering on ewes with their own young present.