Estimation of genetic parameters for body weights of Kurdish sheep in various ages using multivariate animal models
Genetic parameters and (co)variance components were estimated by restricted maximum likelihood (REML) procedure, using animal models of kind 1, 2, 3, 4, 5 and 6, for body weight in birth, three, six, nine and 12 months of age in a Kurdish sheep flock. Direct and maternal breeding values were estimated using the best linear unbiased prediction (BLUP) by DF-REML software. The data used in the present study was obtained from one research flock of Kurdistan Kurdish sheep, including 2476 animals, during the period of 1993 to 2003 (11 years). The log L estimated for all of the six models of this study showed that model 6 was the most appropriate for the analysis of data. Direct heritability values for the traits of this study based on the model 6 (best model) were 0.161, 0.233, 0.260, 0.091, and 0.122, for body weight in birth, three, six, nine and 12 months of age, respectively. Furthermore, maternal heritability (m2) based on the model were 0.238, 0.023, 0.014, 0.005, 0.004, for body weight in birth, three, six, nine and 12 months of age, respectively. Correlation between direct and maternal additive genetic values for body weight in birth, three, six, nine and 12 months of age were 0.0351, 0.5911, 0.7427, 0.7968 and 0.5735, respectively. Direct additive genetic correlations between birth weight and body weight performance at later ages were positive and relatively high, ranging from 0.31 to 0.67, and they were positive and high between weaning and later weights and six month with yearling weight, ranging from 0.54 to 0.79.
Key words: Genetic parameters, (co)variance components, body weights, Kurdish sheep.