EFFECT OF SHORT-TERM DIVERGENT SELECTION FOR BODY WEIGHT AT 4 WEEK OF AGE IN JAPANESE QUAIL UNDER NORTH-SINAI CONDITIONS A. EFFECT ON 4 WK OF AGE BODY WEIGHT

Abstract

The base population of the evaluated Japanese quail was derived from a randomly mated flock. This flock was used for subsequent divergent body weight selection to produce the next three generations (G1, G2, and G3). The resultant investigational birds during the period from November 2016 to November 2017 were produced and raised at the experimental farm, Department of Animal and Poultry Production, Faculty of Environmental Agricultural Sciences, Arish University, Al-Arish, North Sinai, Egypt. Individual selection for body weight at 4 wk of age was applied. The upmost 2/3 ranked birds were considered ‘the high body weight line (HL)’, while the lowest 1/3 ranked ones were considered ‘the low body weight line (LL)’. At 5 wk of age, the selected birds were transferred to cages (1 male and 2 females assigned at random from the same selection category along with avoiding sib mating). The same trend of body weight selection intensity was applied at each generation but within each line. The used experimental diet was a corn-soybean growing diet in a mash form with approximately 23% crude protein and 2850 kcal ME/kg. Feed and water were offered ad libitum. Results indicated that the interaction between body-weight and sex was significant on most evaluated body weights. Furthermore, after three generations of that divergent selection, themagnitude of response to selection showed thatmeans of the third generation surpassed the base population by 15.25% and -22.22% for HL and LL; respectively. Also, the third generation high females surpassed the high males and the difference between them was 8.76%. The response to selection for HL, LL and for divergent body weight at 4 wk were 26.33, -38.13, and 64.46, respectively. However, the low selected line had the highest realized heritability (h2) value (0.64) compared with moderate values in high selected line (0.34 and 0.47). While the ESD / SD ratios showed higher values for HL than LL. The ratio values for LL were very close to unity an indication that natural selection did not influence selection for low 4-wk body weight.