Phenotypic Responses to Selection in Ross 308 Broiler Breeders: Long-Term Growth Assessed With Nonlinear Models...

Area of Science:

• Animal Science
• Quantitative Genetics
• Poultry Breeding

Background:

• Broiler breeder performance is crucial for poultry industry efficiency.
• Understanding genetic and phenotypic trends in growth is essential for effective breeding programs.
• Longitudinal growth data analysis requires robust mathematical modeling.

Purpose of the Study:

• To evaluate phenotypic responses to selection for growth in Ross 308 broiler breeders over four generations.
• To model sex-specific growth trajectories using nonlinear functions.
• To identify the best-fitting growth model for describing population dynamics.

Main Methods:

• Longitudinal body weight records from hatch to 64 weeks were analyzed across four generations (G1-G4).
• Effects of generation, sex, and their interaction on body weight were examined.
• Eight nonlinear growth functions (Gompertz, Richards, Logistic, Brody, von Bertalanffy, Weibull, Hossfeld, López) were fitted and compared using statistical criteria (R², adjusted R², MSE, RMSE, AIC, BIC).

Main Results:

• Significant effects of generation and sex on body weight were observed (p ≤ 0.0001).
• Males were consistently heavier than females, with sexual dimorphism emerging after 4 weeks.
• Fourth-generation birds showed higher body weights than first-generation birds, indicating phenotypic improvement; the Gompertz function provided the best fit (R² = 0.9978-0.999).

Conclusions:

• Consistent phenotypic improvement in growth traits across generations was demonstrated.
• The Gompertz model offers a practical and robust framework for monitoring growth dynamics in broiler breeders.
• Findings support the use of growth modeling in selection and management decisions for enhanced broiler breeder performance.