The survival and development of fertilized eggs transferred between Border Leicester and Merino ewes

Abstract

Fertilized eggs were transferred reciprocally, at a rate of one or three per animal, between Merino and Border Leicester (B.L.) ewes. Recipients were either allowed to go to term or autopsied 14–15 days after transfer. The number of recipients becoming pregnant was not affected by breed of recipient, breed of egg, or number of eggs transferred. The survival rate of eggs transferred at a rate of three per recipient was less than that of those transferred at a rate of one per recipient (55% v. 75%, P < 0.01). Irrespective of breed of egg transferred, Border Leicesters had more triplet and less single pregnancies than Merinos. The vast majority of pre-natal loss occurred early in pregnancy and was evident at autopsy as missing eggs or abnormal embryos. In both single and multiple pregnancies, gestation length was markedly affected by breed of lamb carried (see PDF).In the larger breed (B.L.) gestation was extended when the smaller breed (Merino) was carried, while gestation in the smaller breed was shortened when the larger breed was carried.