GENETIC AND PHENOTYPIC EVALUATION OF EGG PRODUCTION TRAITS IN SELECTION EXPERIMENT PERFORMED ON BENHA CHICKENS

Abstract

A selection program for four generations (base and three selected generations) was started in 2011 in Benha University, Egypt to improve egg production traits in a synthetic line named Benha chickens. A total of 18 cockerels and 180 pullets were selected from Benha base population (control) according to their BLUP values for egg number during 90 days of laying Data of 756 pedigreed hens were used to obtain estimates of heritability, genetic and phenotypic correlations and BLUP for egg production traits, age (ASM) and body weight at sexual maturity (BWSM), weight of the first egg (WFE), egg number (EN), rate of laying (RL), egg mass (EM) recorded during 90 days (EM90D) and 120 days (EM120D) of production after sexual maturity. The selection effects, correlated responses and the genetic and phenotypic trends for egg production traits across generations were quantified and clarified applying the updated approach of the animal model program of BLUPF90. Heritability estimates were moderate; being 0.27, 0.32, 0.42, 0.31, 0.34, 0.28, 0.33, 0.14 and 0.19 for ASM, BWSM, WFE, EN90D, EM90D, EN120D, EM120D, RL90D and RL120D, respectively. The ranges in BLUP of most egg production traits in the control generation were higher than those estimates in the selected generations. Accuracies of BLUP estimates for egg production traits in all generations (control and selected) were moderate or high. The three selected generations were superior in most egg production traits than the base generation (P <0.05) and the contrasts among estimates of these generations were significant (P<0.05). The phenotypic trend increased from 1642 to 1759 g, 28.1 to 30.2 g, 57 to 64 egg, 79 to 84 egg, 2593 to 2977g and 3651 to 4027 g for BWSM, WFE, EN90D, EN120D, EM90D and EM120D, respectively. The genetic trends across the generations clarifying that the initial BLUP estimates for BWSM, WFE, EN90D, EN120, EM90D, EM120D were 12 g, 0.07 g, 0.9 egg, 0.5 egg, 0.57 g and 38 g in the base generation, then gradually increasing as the generation of selection advanced till reached 21 g, 0.03 g, 2 egg, 2.2 egg, 72g and 63 g in the first generation, and reached 32 g, 0.52 g, 3.4 egg, 4 egg, 87 g and 89 g in the second generation and finally 45 g, 0.8 g, 4.8 egg, 5.5 egg, 102 g and 114g in the third generation, respectively. The accumulative correlated selection responses were 140.5 g, 1.99 g, 5.45 egg, 418 g, 371g, 7.52 % and 4.22 % for BWSM, WFE, EN120D, EM90D, EM120D, RL90D and RL120D, respectively.