Growth Models of Female Dairy Cattle

Different methods of representing animal growth are possible and are defined for different animal categories. In this paper, weight measuring of female dairy cattle will be modelled by several nonlinear models. The most commonly used methods for describing the growth of animals are: Gompertz function, logistic function, Schmalhausen function, Brody function, Weibull function, Wood function and Von Bertalanffy function. Measured weight values and estimated parameters of growth curves will be analyzed using regression analysis methods. We will work with the weight measurements of 10 calves under 25 months of age from cowsheds in village Zaluži in the Czech Republic. A comparison of several growth curves will be done. The suitability of individual models will be evaluated not only by the index of determination, but also by the intrinsic curvature according to Bates and Watts. This curvature affects the size of the linearization areas in which initial solution will ensure convergence of nonlinear regression.