Genetic parameters, phenotypic and genetic trends of litter size on different breeds of goats in Egypt.

Data of 475 goats (242 Zaraibi, 84 Baladi, and 149 Damascus) kept at Sakha Farm, belonging to Animal Production Research Institute (APRI), Ministry of Agriculture, Dokki, Cairo, Egypt, from the period of 2011 to 2017 were used to estimate direct (additive) and maternal genetic effects for litter size at birth (LSB). Three animal models were used. Model 1 includes the fixed effects of breed, season, year of kidding, age of doe, and direct genetic effect. Model 2 is similar to model 1 beside the permanent environmental effect. Model 3 is similar to model 2 and includes the maternal genetic, covariance between direct and maternal genetic effects. The effects of breed, season, year of kidding, and age of doe were significant on LSB. Heritability estimates for LSB are 0.19±0.050, 0.19±0.160, and 0.06±0.007, as estimated from models 1, 2, and 3, respectively. Maternal heritability estimate using model 3 was 0.05±0.006. The removal of additive genetic maternal effect and covariance between direct and maternal effects from the model increased heritability of direct genetic effect by 0.13. Annual phenotypic trends for LSB in Zaraibi, Baladi, and Damascus goat breeds are negative. Annual genetic trends for LSB for the three breeds of goats are positive, significant, and being 0.10±0.01, 0.25±0.02, and 0.01±0.001 litter/year for Zaraibi, Baladi, and Damascus, respectively. The present results indicated that selection for LSB will take a long time. The speed and efficiency of selection is expected to increase by use of molecular markers in selection.