Effects of Genetic Selection on Growth, Nutritional Value, and Amino Acid Profiles of Breast Muscle and Blood in Black-Boned Chickens.

Thai black-boned chickens, a native genetic resource valued for their dark-pigmented meat and blood with reputed functional properties, generally exhibit slower growth than commercial broilers. The potential for selective breeding to enhance growth performance while maintaining their unique nutritional and functional characteristics remains unclear. We compared growth performance and nutritional profiles of breast meat and blood between a genetically selected line and an unselected control, and evaluated sex and tissue effects. Two lines were reared under identical management (n = 200 chicks). Body weight (BW) was recorded from hatch to 16 wk; average daily gain (ADG) and breast circumference (BrC) were calculated at 0-4, 0-8, 0-12, and 0-16 wk and at 8, 12, and 16 wk, respectively. At 16 wk, 48 birds (12/sex/line) were sampled for proximate nutrients and amino acids in breast meat and whole blood. Data were analyzed using two-way ANOVA. The selected line outperformed the unselected line across all growth traits. Mixed-sex BW rose from 33.10 g at hatch to 1456.21 g at 16 wk versus 30.26 g to 1228.81 g in controls (18-19% higher at market age). ADG was greater in the selected line at every interval (14.27 vs. 11.24 g/day at 0-16 wk), with the largest advantage during 12-16 wk. BrC was consistently larger in genetically selected line (average 26.98 vs. 24.81 cm at 16 wk). Sex dimorphism was evident, with males showing the greatest response. Nutrient analyses showed higher total energy and fat contents in selected breast meat, whereas blood cholesterol and minerals (Na, Ca, Fe) levels were lower, particularly in the unselected line. Amino-acid profiling revealed higher concentrations of key essential amino acids (lysine, threonine, Branched-Chain Amino Acids; BCAAs) and major non-essentials (glutamic, aspartic acids) in the breast muscle of the selected line; most amino acids were greater in muscle than blood, with significant line × tissue interactions. Genetic selection substantially improved growth rate, breast development, and nutritional quality of breast meat while altering mineral and cholesterol distribution between tissues. These gains support selective breeding as a practical strategy to enhance productivity and functional values in black-boned chickens.