Embryo survival in mature Romney ewes relative to live weight and face cover

Abstract

In Experiment I fertilised eggs were transplanted at the rate of I, 2, or 4 per recipient ewe and these animals were autopsied in early pregnancy. In Experiment 2 ewes were mated to fertile rams and autopsied 18-30 days later. Some of these ewes had not conceived to egg transfer (Expt I).Transfer of I, 2, or 4 eggs did not affect the percentage of ewes which became pregnant. An ovum had a greater chance of surviving if transferred singly rather than as one of a multiple number of eggs.The number of corpora lutea (lor 2) did not affect the rate of survival of transferred ova or survival of ova in mated ewes.No significant relationship existed between live weight of the ewe and survival of ova.Face cover was related (P < 0.01) to rate of survival of ova among ewes transplanted with 2 eggs each, but no clear effect was apparent in the other ewes after egg transfer or in the mated ewes.

A study of relationships of breed, time of mating, level of nutrition, live weight, body condition, and face cover to embryo survival in ewes

“…That live weight may influence embryo survival might be inferred from the reported increase in barrenness found in ewes of low live weight (Coop, 1962), from studies of Bennett et al (1964) and Edey (1970a, b) which both reported effects of undernutrition in light but not heavy ewes. Cumming & McDonald (1970) found no significant relationship between live weight and survival of transplanted ova in ewes of medium and high live weight. In the present study ewes of low live weight were not included and the study failed to confirm that live weight or body condition were important factors affecting embryo I .…”

Survey observations on the reproductive performance of both romney stud and commercial flocks throughout New Zealand

“…Coop (1964) also observed increased barrenness in ewes of low body weight. These observations have been challenged by Cockrem (1965), and Cumming and McDonald (1970) presented data that suggest no relationship between live weight at mating and the degree of embryonic loss.…”