Estimation of genetic parameters for production traits of Chios sheep using a multitrait animal model

Genetic parameters for commercial milk yield, litter size at birth and mean litter weight at weaning of Chios sheep were estimated. The data originated from the Agricultural Research Station of Chalkidiki and included 5343 lactations of 2315 ewes with lambings from 1977 until 1996. Variance components were estimated using restricted maximum likelihood, fitting a multitrait animal model. The random effects included in the model were the additive genetic effect of the animal, the effect of the permanent environment of the animal and the residuals. Heritability estimates were 0.23+/-0.015, 0.16+/-0.011 and 0.16+/-0.010, for commercial milk yield, litter size at birth and mean litter weight at weaning, respectively. In the same sequence the repeatabilities of the traits were 0.38, 0.18 and 0.16. Genetic correlations were 0.03+/-0.040 between milk yield and litter size, - 0.77 +/- 0.036 between litter size at birth and mean litter weight at weaning and - 0.06+/-0.037 between milk yield and mean litter weight at weaning. (C) 2000 Elsevier Science B.V. All rights reserved.