Growth curve of half-breed goats in the Paraíba State

Abstract

This research was developed to evaluate some mathematical models cited in the literature to the growth adjustment curve as well as to determine mathematical models that significantly represent the growth curve of half-breed goats. It was used data of 90 animals born from April 1997 to September
1998 reared in the goat farm of Campus IV, UFPB, Bananeiras-PB. Twenty-seven 27 weights were recorded for each animal, every 7 days until the animals reached 182 days old, totalizing 2,430 weights. The adjustment to the average curve was done by six mathematical models: Von Bertalanffy, Brody, Incomplete Gamma, Hyperbolic Linear, Quadratic Polynomial Exponential and Logarithmic Quadratic. The parameters for the mathematical models were estimated by the method of GAUSSNEWTON, with a non-linear regression. The criteria used to verify the quality of the adjustment for each model was the adjusted determination coefficient (R²_a) and residual distribution graphics. The R²_a values obtained for the models were 97%. The growth average curve estimated by the Logarithmic Quadratic models and Quadratic Polynomial Exponential express better the weight variations in growth and show less residue with a slightly superiority for the Logarithmic Quadratic model.