Evaluasi Penerapan Model Matematik Nonlinear Dalam Memprediksi Laju Pertumbuhan Sapi Brahman Cross Di PT Buli = Evaluation of Application ofNon Linear Mathematical Models Prediction of Growth Rate of Brahman Cross Cows i

Abstract Cross-Sectional data of age and weight of 1504 Brahman Cross (BX) females from less than one month to 66 months of ages were obtained from ranch and feedlot system in PT BULI (Berdikari United Livestock Indonesia) and used in this study. The objectives of this study were to evaluate the application of nonlinear mathematical models: Brody, Bertalanffy, Logistic, Gompertz and Richards models in predicting growth rate of BX female. Weight data were collected from weighing and the average body weight of age groups were fitted to the five mathematical models. SPSS program of non linear regression was used to obtain the estimate of the parameter of the five models. The results showed that the R: obtained from the five mathematical models were greater than 90%. Mathematically, this study showed that the best model was Brody model and followed by Bertalanffy, Gompertz, Richard and Logistic model in predicting of age and weight of cows. The predicted of growth rate of birth for the Logistic and Gompertz model was 7.82 kg/mo and 10.42 kg/mo respectively while the actual value was 7-11 kg/mo. Then the onset of puberty was predicted as 10.31 kg/mo and 11.13 kg/mo respectively while the actual value was 9-12 kg/mo. Logistic and Gompertz models were recommended to predict growth rate criteria (birth and onset of puberty) Keywords: puberty - growth - brahman cross-cows � Mathematical Non Linear Mode