Genetic Parameters of Direct and Maternal Effects for Birth Weight of Friesian Calves under Egyptian Farm conditions

A total of 4889 birth weight (BW) records on calves of 1609 Friesian cows in Sakha experimental farm were collected between 1975 and 2020 year. The analytical model included the fixed effects of the parity, calving year and season, age at first calving, gestation period length and calf sex. Variance components, heritabilities, direct maternal correlations and breeding values (BV) were estimated using VCE6 program . Genetic trends of calves BW were evaluated by regressing BV on years of calving using GLM process of SAS software. Results showed highly (P≤ 0.001) significant effects of all studied fixed effects on BW. Direct (h 2a ), sire (h 2s ), maternal (h 2m ) and total (h 2t ) heritabilities and direct maternal correlations (r am ) estimates were 0.01, 0.10, 0.05, 0.09 and 0.01, respectively. Estimated BVs of calves, sires and dams ranged from -6.71 to 6.84, -6.04 to 4.38 and -7.29 to 8.86 kg, respectively. Range of BVs for dams was higher than for sires and calves, but the accuracy of calves BVs were higher than others. The genetic trend was not different from zero showing no indication of change in the genetic merit of BW in this farm during the period of study.Dam selection proved to be important for inducing high genetic progress in BW during the subsequent generation. Moreover, BV estimates of calves BW achieved higher accuracy ranging from 0.69 – 0.81% comparing to those for sires and dams by indirect selection. However, improvement in calves BW may also be achieved by practicing better management programs in this herd.