Application of non linear models in estimating growth curves of body weight and sizes of Holstein-Friesian female cattle

Abstract

Aplication of non-linear mathematical models in estimating growth curves of Holstein- Friesian (HF) females were tested. Body weight and measurements were conducted for various ages of HF females, succesively for calves 54 hd, heifers 84 hd and adults 348 hds in a west area of KPSBU Lembang, West Java in July-August 2007. Body weight was converted from chest girth using a Gompertz tape. Growths of body weight and sizes generally formed sigmoid pattern, increased rapidly from birth, reached maximal around 9.58 mo (an estimated pubertal age), then slowed to an almost constant at the age of ≥52 mo. Three non-linear models used in estimating growth curbes were logistic, von Bertalanffy and Gompertz respectively. Comparison of the best model was 2 determined for the highest determinant coefficient (R ) and the lowest mean square of error (MSE). Gompertz and von Bertalanffy models were considered as the two most appropiate models due to
2 their almost similar values in R and MSE. The easiness in developing model measured by counting lowest iteration number was succesively for von Bertalanffy, Gompertz, and Logistic. Logistic model predicted better in biological aspects as its closer predicting pubertal age (around 9.58 mo), but the two remaining were better from the mathematical aspects due to easier and more suitable uses.