Objective  To investigate a better model to support crossing system of Green-shell chickens.

Method  The hens of Green-shell chicken (LK) and two cross combinations of Jiuyuan black cocks×Green-shell layers (JL) and Green-shell cocks×Luhua layers (LL) at the age of 300-day-old were randomly sampled. Their body sizes and slaughter performance were measured. The correlations between body sizes and slaughter performance were analyzed and the best regression equations for carcass traits were established.

Result  The chest depth and shinbone girth of LL were shorter compared with LK and JL, while the shank length was longer. The comb height of LK was the highest among three groups. The average living body weights for 300-day-old hens from three populations were more than 1 700 g, their slaughter rates were over 87%, and the eviscerated rates of LK,JL and LL were 53.50%, 59.35% and 61.39%, respectively. As for LL, its subcutaneous fat thickness was greater compared with other groups, its breast muscle rate was higher than that of JL, and its abdominal fat weight and abdominal fat rate were less than those of JL (P<0.05). The eviscerated carcass rates of LL and JL were greater than that of LK, and the breast muscle rates of LK and LL were greater than that of JL. The correlations between slaughter performance and some body size traits such as shinbone girth, keel length and chest depth were significant (P<0.05). The optimal linear regression equations of slaughter performance and body measurement traits were established. TheR² for regression models of half-eviscerated weight, eviscerated weight, subcutaneous fat thickness, eviscerated rate and breast muscle rate were above 0.4.

Conclusion  LL has better meat performance compared with LK and JL. Shinbone girth, keel length, and chest depth can be used as indirect indexes for selecting slaughter performance of Green-shell chickens. We have successfully established regression equations for evaluating slaughter performance through body size traits.