This study aimed to investigate the effects of selection for high early growth rate during 1-21 days of age (GR1-21) on growth traits, some plasma constituent and carcass characteristics. An experiment was carried out at the farm of the Poultry Research Center, Faculty of Agriculture, Fayoum University and continued for six generations including 10,024 for two lines (the selected line, HGR1-21 and the control line, CL) of Japanese quail chicks. The HGR1-21 had better BW21, BW35, GR1-21, GR1-35 and BWG1-35 than the CL. Generation of selection significantly affected all growth traits. Females had significantly higher BW21, BW35, BWG1-35 and GR1-35 than males.
Quails of HGR1-21 had lower high density lipoprotein (HDL) and higher triglycerides (TG) than the CL. Females had higher TG and lower HDL than males. Quails of HGR1-21 had higher carcass %, dressing %, weights of giblets, heart, gizzard and liver than CL by 3.65%, 2.59, 23.79, 68.42, 13.21 and 23.47%, respectively. Females had higher weights of giblets, gizzard and liver than males by +12.41%, 14.64% and 12.34%, respectively. The HGR1-21 had higher ether extract % (+24. 28%) and lower moisture% (-4.79%) than the CL. GR1-21 showed moderate heritability (h2) of 0.28 and ranged from 0.20 to 0.29 for growth traits. The GR1-21 found to be positively genetic and phenotypic correlated (rg & rp) with BW21, BW35, BWG1-35 and GR1-35, with rg ranged from moderate to high (0.24 to 0.70) and rp ranged from low to medium (0.03 to 0.41), however there were negative rg and rp between GR1-21 and BW1 being -0.15 and -0.50,respectively. Genetic response showed superiority of the selected line than the control (P< 0.05) for selection criteria (+0.04) .Selection for GR1-21 had desired genetic gain with all studied growth traits, except BW1. Also, carcass traits and vital organs were improved due to selection for GR1-21.