Fitting and analysis of growth curve of Anyi gray chicken

<bold>Objective</bold> This study aims to fit the growth curve of Anyi gray chickens using nonlinear models to investigate their growth patterns and provide a theoretical basis for production. <bold>Method</bold> A total of 100 fertilized eggs were collected from the Anyi Gray Chicken breeding farm，and 91 chicks were hatched.The chickens were reared in mixed-sex multilayer cages from 0 to 6 weeks and in free-range groups under woodland from 7 to 18 weeks.Body weights were measured at 0，2，4，6，8，10，12，14，16，and 18 weeks of age.Three nonlinear models Logistic，Von Bertalanffy，and Gompertz were applied to fit the growth curves of male and female Anyi gray chickens. <bold>Result</bold> All three models achieved <italic>R</italic>² values above 0.99.The Von Bertalanffy model showed the best fit for males，while the Gompertz model was optimal for females，both with <italic>R</italic>² values of 0.998.The inflection point of the body weights for male and female chickens were 782.89 g and 469.39 g，respectively，and the inflection point of ages were 9.21 weeks and 7.51 weeks，respectively.The weight of cocks in this breed was significantly（<italic>P</italic>&lt;0.05）higher than that of hens in each week.Males reached their peak growth rate at week 10，whereas females reached it at week 8. <bold>Conclusion</bold> The Von Bertalanffy model is identified as the most suitable for male Anyi gray chickens，with the equation：W=2 642.25×（1-0.807e^-0.096<italic>^t</italic> ）³.The Gompertz model is optimal for females，with the equation：W=1 275.95e^{-3.747×exp（-0.176}<italic>^t</italic>^）.