Comparative study of fitting various lactation curve models in Holdeo crossbred cattle

Abstract

The present investigation was carried out on 838 weekly test day milk yield records of first lactation pertaining to 411 HF x Deoni (Holdeo) crossbred cows spread over 38 years located at Cattle Cross Breeding Project, Vasantrao Naik Marathwada Krishi Vidyapeeth, Parbhani (Maharashtra). The comparison of four lactation curve models viz, Parabolic exponential function, Wood’s gamma function, Quadratic model and Mixed log function was made in the present investigation. Mixed log function described as an excellent model for prediction of WTDY with the highest coefficient of determination (99.01 %) with comparatively lowest root-mean-square error (0.16 kg) value. The quadratic model was least fit model with the lowest coefficient of determination (90.76 %) and the highest root-mean-square error (0.51 kg) among the four models in Holdeo. The predicted error in WTDY in Parabolic exponential function, Wood’s gamma function and mixed log function were the highest in WTDY5 and in Quadratic model it was highest in WTDY6. The errors between the observed values and predicted values were highest during the peak phase in all four models. The errors in estimated and predicted WTDMY values in initial milk yield of Holdeo cows were lower than the peak yield. The ascending phase of lactation curve was shorter than the descending phase. The gamma type function when compared to mixed log function, explained low peak yield and it is recommended that this function can give the best fit for the low yielding cows.