The performance of the chicken stocks differs substantially in muscle weight and carcass weight, according to Juan Li and colleagues at Sichuan Agricultural University in Ya’an.

They investigated how dietary lysine affects chickens from local Chinese pure lines and their reciprocal crosses, publishing a paper in Poultry Science.

The objective of their experiment was to evaluate the effect of dietary lysine concentration on meat quality and carcass traits in two chicken lines, SD02 and SD03, and their crosses, both originating from a Chinese native breed, the Erlang Mountainous chicken.

The lines were selected for four generations by the University; for the present study, chickens from the two lines and their crosses were randomly assigned at hatch to one of two dietary groups. One group was offered diets containing 1.00, 0.85 and 0.70 per cent total lysine, whereas the other was offered diets with 1.15, 1.00 and 0.85 per cent total lysine from day 1 to 28, day 29 to 49, and day 50 to 70, respectively. In total, 252 chickens were commercially processed at 70 days old.

Traits measured included live bodyweight, subcutaneous fat thickness, weight of carcass, eviscerated carcass, semi-eviscerated carcass, breast muscle (left pectoralis major and minor), leg muscle (boneless left drum plus thigh), heart, gizzard, proventriculus, spleen, liver, comb, and abdominal fat, color parameters lightness, redness or yellowness (L*, a*, and b*), pH, and breast muscle intramuscular fat content.

The results indicated that, although dietary lysine concentration did not affect subcutaneous fat thickness, colour parameters, pH, intramuscular fat content and organ weights, there were effects on feed conversion and muscle and body weights (P<0.05).

Li and co-authors noted that males and females displayed major differences in feed conversion, bodyweight, muscle growth and organ weight. The Line SD02 chickens grew faster and displayed less fat deposition and superior feed conversion than Line SD03 and the reciprocal crosses.

Reference

^{Li J., X-L. Zhao, Y-C. Yuan, E.R. Gilbert, Y. Wang, Y-P. Liu, Y. Zhang and Q. Zhu. 2013. Dietary lysine affects chickens from local Chinese pure lines and their reciprocal crosses. Poult. Sci. 92(6):1683-1689. doi: 10.3382/ps.2012-02865}