Dietary lysine affects chickens from local Chinese pure lines and their reciprocal crosses

The objective of this experiment was to evaluate the effect of dietary lysine concentration on meat quality and carcass traits in 2 chicken lines, SD02 and SD03, and their crosses, both originating from a Chinese native breed, the Erlang Mountainous chicken. The lines were selected for 4 generations by Sichuan Agricultural University (Ya'an, China); for the present study, chickens from the 2 lines and their crosses were randomly assigned at hatch to 1 of 2 dietary groups. One group was offered diets containing 1, 0.85, and 0.70% total lysine, whereas the other was offered diets with 1.15, 1, and 0.85% total lysine from d 1 to 28, d 29 to 49, and d 50 to 70, respectively. In total, 252 chickens were commercially processed at 70 d old. Traits measured included live BW, 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, color parameters, pH, intramuscular fat content, and organ weights, there were effects on feed conversion and muscle and BW (P < 0.05). Males and females displayed major differences in feed conversion, BW, muscle growth, and organ weight. The Line SD02 chickens grew faster and displayed less fat deposition and superior feed conversion compared with Line SD03 and the reciprocal crosses. In conclusion, performance of the chicken stocks evaluated in this study differs substantially in muscle weight and carcass weight.