EFFECTS OF EWE GENOTYPE AND SUPPLEMENTARY FEEDING ON LAMBING PERFORMANCE OF ETHIOPIAN HIGHLAND SHEEP

摘要

Groups of Menz (M), Corriedale X Menz (CM), and Awassi X Menz (AM; n=41, 41 and 36, respectively) ewe lambs were studied between weaning and birth of their first lambs (sired by M rams) in the cool highlands of central-northern Ethiopia. Between age 6 and 13 months, the ewe lambs were run continuously with fertile M rams. Sixty-eight (58%) conceived, and neither age at first lambing (AFL; mean 471+/-6 d) nor the proportion of lambing (49 to 71%) was influenced by genotype or supplementation. Age at conception was not significantly related to body weight, and at comparable ages, ewe lambs which conceived or did not conceive had similar BW. Genotype and supplementation, and their interaction, had significant effects on post-partum ewe BW (PPEBW): CM and AM were heavier than M (22.9+/-0.9 and 24.1+/-0.9 vs. 19.0+/-1.0 kg; P<0.01), supplemented ewes were heavier than controls (25.3+/-0.8 vs. 18.7+/-0.7 kg; P<0.001), and interaction showed that CM and AM responded more to supplementation (P<0.05). Lambs from M dams were lighter at birth than from CM and AM (1.5+/-0.2 vs. 1.9+/-0.1 and 2.2+/-0.1; P<0.05), but from supplemented ewes were not significantly heavier than controls (2.0+/-0.1 vs. 1.8+/-0.2 kg). Genotype X supplementation interaction for lamb BW was not significant. Crossbreeding M, a polyestrous breed, with C and A breeds with long breeding seasons, did not significantly influence age or weight at puberty, and those two traits were not significantly related. Cross-breeding significantly increased lamb BW and PPEBW, and supplementation significantly increased PPEBW, which indicates that natural pastures were insufficient in quantity and quality to sustain ewes at the BW of which they were genetically capable.