GENETIC AND ENVIRONMENTAL TRENDS OF EARLY GROWTH TRAITS IN THE ELSENBURG DORMER SHEEP STUD

Data from the Elsenburg Dormer sheep stud were used to estimate geneti c and environmental change in early growth traits from 1943 to 1990. B est linear unbiased predictions (BLUP) of breeding values were obtaine d by Restricted Maximum Likelihood (REML) procedures fitting a direct additive and maternal additive genetic model. Environmental change, ca lculated as the difference between phenotypic and genetic values, was found to be negative for all traits studied. Genetic trends were small er but significantly positive. The higher maternal trends reveal that the biggest genetic improvement was in the additive genetic ability of ewes to produce faster growing or heavier lambs. The relative low but linear genetic trends suggest that selection pressure on these traits was low during the 48 years, probably owing to higher selection empha sis on traits other than the growth traits studied.