The effect of nutrition before mating on the reproductive performance of Merino ewes

Abstract

A factorially designed trial was used to study the effects of level of nutrition on the reproductive performance of Merino ewes. A high level of nutrition from three weeks before joining to conception (flushing) increased the percentage of twin births independently of the effects of previous levels of nutrition. Levels of nutrition did not affect the number of ewes that lambed. Flushing increased body weight and body condition score. Re-analysis of the results showed that there was an association between both body weight gain and body condition score and percentage of twin births. However, body weight gain and body condition score increase during flushing were associated with levels of nutrition before flushing. Although flushing increased body weight of groups at conception, on re-analysis of the results, the percentage of twin births could not be associated with weight at conception. Possible reasons for this result are suggested. As there was no indication of a significant relation between weight at conception and percentage of ewes that lambed, it is suggested that the critical weight for mating these ewes was below 38.7 kg.