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Genetic, Environmental and Interaction Effects in Sheep II. Lamb Growth and Carcass Merit^{1, 2,}

Oregon State University, Corvallis 97331

Abstract

Genetic, environmental and interaction effects on lamb growth and carcass merit are reported from a diallel cross among three breeds replicated over 3 years and two grazing management systems. Breeds were the Suffolk, Hampshire and Willamette, and management systems were hill pastures vs irrigated pastures. Year, sex, age of dam, and type of birth and rearing effects on growth rate were consistent with reports from the literature. Year, sex and carcass weight significantly influenced carcass variables. Hill pasture lambs were larger at birth, grew more rapidly and had superior carcass cutability. For weaning weight and carcass weight per day of age (WDA), Suffolks were superior in both additive and maternal genotypic effects and Hampshires were poorest. Hampshires excelled for carcass conformation and Suffolks for carcass cutability. On irrigated pastures, there was little sire breed variation for growth, carcass finish score and carcass quality grade, but on hill pastures breed differences were indicated for these traits. Sires accounted for 1 to 2% of total variation for growth traits and from 3 to 11% for carcass traits. Heterosis for weaning weight and carcass WDA was about 6%. Significant differences between reciprocal crosses for percent heterosis always favored the reciprocal cross whose female parent had the higher estimate for maternal component. Heterosis for carcass traits was not significant. No mating system x management system interactions were detected.

¹ Technical Paper No. 3867, Oregon Agricultural Experiment Station.

² Contribution to Western Regional Project W-61, The Development of Selection Criteria for the Genetic Improvement of Carcass Merit in Sheep.

³ Department of Animal Science.