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Describing growth pattern of selected Kedah-Kelantan cows using non-linear regression models

Mohd. Hafiz¹, A.W, Marini², A.M., Rosly³. S.M., Mohamad Hifzan³, R., Izuan Bahtiar², A.J. and Shanmugavelu¹, S.

¹Livestock Science Research Centre, , MARDI Muadzam Shah, 26700 Muadzam Shah, Pahang
²Livestock Science Research Centre, MARDI Kemaman, 24007 Kemaman, Terengganu
³Livestock Science Research Centre, MARDI Headquarters, P/O Box 12301, General Post Office, 50774 Kuala Lumpur

Malaysian J. Anim. Sci. 2019 22(1): 47-54

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The objective of this study was to evaluate the best fit non-linear regression model to describe the growth pattern of Kedah?Kelantan (KK) cows.   Estimates of asymptotic mature weight, rate of maturing and constant of integration were derived from Brody, von Bertalanffy, Gompertz and Logistic models which were fitted to cross-sectional data of body weight taken from 81 KK cattle with the age ranging from birth to 96- mo old.  Coefficient of determination (R2) and residual mean squares (MSE) were used to determine the best fit model in describing the growth pattern of KK cows.  Von Bertalanffy model showed the best goodness of fit as explained by its highest R2 and lowest MSE (0.9686 and 720.9, respectively), followed by Gompertz (0.9681 and 733.6, respectively), Logistic (0.9667 and 766.8, respectively) and Brody (0.8683 and 793.2, respectively). The correlation between rate of maturing and mature weight was found to be negative in the range of -0.7154 to -0.9213, indicating that animals of heavier mature weight had lower rate of maturing.  The use of non-linear model could summarize the weight-age relationship into several biologically interpreted parameters compared to the entire lifespan weight-age data points that are difficult to interpret.  The study of growth pattern also important to determine the optimum weight and age for replacement heifer and slaughter besides to strategize the feeding regime for maximum productivity.