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

## TL;DR

Genetic selection in black-boned chickens improved growth and breast meat quality, with higher amino acids and energy, but altered blood cholesterol and minerals.

## Contribution

Demonstrates that selective breeding can enhance growth and meat nutritional profiles in black-boned chickens.

## Key findings

- Selected chickens showed higher growth rates and larger breast size at all ages.
- Selected line breast meat had higher energy, fat, lysine, and branched-chain amino acids.
- Unselected line had higher blood cholesterol and minerals, with sex differences observed.

## Abstract

This study compared two lines of black-boned chickens: one selected for growth and one unselected. We measured body weight, daily growth, and breast size, and tested nutrient and amino acid composition in breast meat and blood. The selected line exhibited a higher growth rate and larger breast size across all ages. Their breast meat contained more energy and slightly more fat, while the unselected line showed higher blood cholesterol and mineral contents. Breast meat—especially from the selected variety—was enriched with key amino acids such as lysine and the branched-chain amino acids. These results suggest better meat quality and higher farm returns from genetic selection.

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.