Evaluation of growth curves in three local quail lines using four diverse non-linear models

Aim of study: To examine growth patterns in three local quail lines using various flexible growth functions and to identify the most suitable non-linear model for describing their growth performance. Area of study: The research was conducted and validated at Salahaddin University-Erbil’s Quail Research Hall, Grdarasha Station, Department of Animal production and health, and College of Agricultural Engineering Sciences. Material and methods: A total of 540 quail chicks from three local lines (Desert, Brown, and White) were studied to evaluate growth patterns using four non-linear models (Gompertz-Laird, Logistic, Richards, and Von Bertalanffy). Model comparisons were based on coefficient of determination (R²), adjusted coefficient of determination (R²adj), akaike’s Information Criterion (AIC), and Bayesian Information Criterion (BIC) to determine the best fit. Growth parameters, including asymptotic weight (β0), maturity index (β0), inflection point weight (IPW), and inflection point time (IPT), were estimated. Main results: Both genetic line and sex significantly influenced growth parameters, with Desert quails showing superior growth performance and higher body weights than Brown and White lines. The Gompertz model provided the best fit, based on higher R² and R²adj values and lower AIC and BIC values. Desert quails had the highest asymptotic weights (β0), while White quails exhibited the highest maturity index (β0), suggesting faster growth rates, and Desert quails had higher IPW and IPT values, with females maturing later than males. Research highlights: The findings give beneficial insights for improving quail breeding programs that can enhance their growth efficiency and meat yield.