Genetic evaluation of growth in Raini goat using random regression models

A number of 10,606 body weight (BW) records of 3908 Raini goats from 153 sires and 1072 dams were used to estimate direct and maternal genetics, direct permanent environmental, and maternal permanent environmental effects on growth from 1 to 410 days of age. The data were collected during 1996 to 2007 from a flock of Raini goat in breeding station in Kerman province; Iran. Random regression (RR) models, including age of dam, sex of kid, type of birth, month and year of birth were used as fixed effects. Also, animal, dam, animal permanent environmental, and maternal permanent environmental as random effects, were fitted to the data using second to fifth order of fit in different combinations of Legendre polynomials for age of kid. Comparisons among different models, based on the Akaike's information criterion, and the Bayesian-Schwarz information criterion were used to select the best model for analyses. The best fitting RRM was the model with a Legendre polynomial of fifth order for direct and maternal genetic effects and fourth order for individual and maternal permanent environmental effects. Direct heritability increased from 0.14 at 20 days of age to 0.38 at 150 days of age then decreased suddenly to 0.18 at 270 days of age and increased thereafter. Maternal heritability increased (except 20 days) to 150 days and then declined moderately until 360 days of age. Genetic correlations among weight at various ages were positive, low to high and ranged from 0.10 between 20 and 360 days of age to 0.99 between 70-90 and 150-180 days of age. The genetic and phenotypic correlations between weights increased with decreasing interval between weights. The low value of genetic correlation (0.10) between early (20 day) and late (360 days) weights implies that early weights are not under the same genetic control as weights at older ages.