The influence of genotype and ewe body condition on reproductive performance

Abstract

Ewes from 5 genotypes-Naeemi, Chios, Texel, Border Leicester Merino (BLM) and Naecmi x Border Leicester Merino-were scored for body condition before breeding and their reproductive performance was compared. Large differences were detected between genotypes with respect to fertility, prolificacy, birth weight and litter weight. Birth weight of lambs born to Naeemi ewes was lesser than the lambs born to BLM, Texel and Naeemi x BLM ewes (P<0.05). Birth weight of Nacemi and Chios lambs was similar. Litter weight was higher for the BLM ewes, and this genotype also had the highest prolificacy. Naeemi ewes had the lowest fertility. Fatness of ewes described as body condition score (BCS) varied at breeding from 2-5 and had significant effects on birth weight. There was tendency for the birth weight to decrease with increasing BCS. Birth weights of lambs were significantly higher (P<0.05) for ewes with BSC up to 3 and lower for ewes with scores over 3. The coefficient of regression on birth weight on Bes was -0.41 ± 0.08 (P<0.01). Fertility, prolificacy and litter weights were not affected by Bes although ewes with higher scores tended to produce lower litter weights. The results show that ewes should be maintained in a moderate condition (BCS = 3) for breeding to produce lambs with heavier birth weights. Fat ewes(BCS>3) have the tendency to increasE their own body weight rather than lamb birth weight. Body condition scoring system could be used to optimize dietary requirements of breeding ewes and birth weight oflambs.