The Curves Fitting for Laying Rate and Cumulative Egg Production, and the Correlation Analysis for Laying Performance of Jiuyuan Black Chickens

Purpose To investigate the laying-egg rule of Jiuyuan black chickens.

Methods In the present study, their performances at laying first egg and for 300 days were recorded, and different nonlinear models were used to analyze the egg laying rate (Wood model, McMillan model, Yang-Ning model and Cubic equation) and the number of accumulated eggs (Logistic, Gompertz, and Von Bertalanffy) of Jiuyuan black chickens aged from 23 to 43 weeks old, and the fitted values were compared with observed values.

Results The variation coefficients of the age at first egg and egg weight of Jiuyuan black chicken were below 10%, while the variation coefficients of egg production for 300 days, body weight at first egg and 300 days were 27.46%, 13.95%, and 12.30%, respectively. Age at first egg was negatively correlated with body weight at first egg and the egg production for 300 days, and body weight for 300 days was significantly positive correlated with body egg weights at first egg (P<0.05), respectively. The results of curve fitting of laying rate showed the fitting degree of Yang-Ning model was optimum (R²=0.935), followed by McMillan model (R²=0.928), Cubic equation (R²=0.844), and Wood model (R²=0.536). The R² for total egg number fitting models of Logistic, Gompertz, and Von Bertalanffy were 0.990, 0.996, and 0.998, respectively. Moreover, the Von Bertalanffy model was closer to the observed values, compared with other models.

Conclusions The uniformities of the age at first egg and egg weight were better, while the body weight and egg production for 300 days needed to be improved. In general, first laying performances were important index for selecting egg production and body weight for 300 days of Jiuyuan black chickens. Yang-Ning and Von Bertalanffy models were most suitable to fit laying rate and total egg number curves, respectively. And they could be used to evaluate and predict the laying-egg performance of Jiuyuan black chicken.