Introducing alternative nonlinear models to characterize growth curves in goats.

By applying some alternative nonlinear functions (such as the sinusoidal, Canter, and Lomolino), this study aimed to introduce these functions in research on the weight development of goats using goat growth data from the literature and their comparison with some routinely used growth models such as Monomolecular, Bridges, Janoschek, Von Bertalanffy, Richards, Schumacher, Morgan, and weibull. During the fitting of nonlinear regression curves, model performance was evaluated and model behavior was examined. The data used in this study came from two published articles reporting (i) body weight records on 120 male Beetal goats recorded at monthly intervals from birth to one year of age, and (ii) body weight records of 50 male South African non-descript indigenous goats. The adjusted coefficient of determination, root mean square error, Akaike's information criterion, and Bayesian information criterion were used to evaluate each model's overall goodness-of-fit to different data profiles. The models typically provided a good fit to the data, as evidenced by the generally high adjusted coefficient of determination values for each model. The selected sinusoidal equation accurately describes the dynamics of goat growth. Among the most effective functions for describing age-related fluctuations in goat body weight was the sinusoidal equation, which was found when comparing growth functions using the fitting criteria. Overall, this study offers implications for advancing research on goat production systems and provides insightful information on the application of alternative nonlinear models, particularly the sinusoidal equation, in modeling goat growth.