Comparison of different lactation curve models in Sahiwal cows

Authors : Vilas DONGRE, Ravindar Singh GANDHI, Avtar SINGH

Pages : 723-726

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Publication Date : 0000-00-00

Article Type : Research Paper

Abstract :The present investigation was carried out on 12,859 fortnightly test-day milk yield records of first lactation pertaining to 643 Sahiwal cows spread over a period of 49 years insert ignore into journalissuearticles values(1961-2009);, maintained at the National Dairy Research Institute, Karnal, India. The comparison of 3 lactation curve models, i.e. the quadratic model, gamma-type function, and mixed log function, was done using fortnightly test-day milk yield records. The mixed log function was the best fit, with the highest insert ignore into journalissuearticles values(88.75%); coefficient of determination insert ignore into journalissuearticles values(R2 value); and the lowest insert ignore into journalissuearticles values(0.08 kg); root mean square error insert ignore into journalissuearticles values(RMSE); value, whereas the lowest insert ignore into journalissuearticles values(56.93%); R2 value was observed in the quadratic model with maximum insert ignore into journalissuearticles values(0.15 kg); RMSE value. The closeness of fit of the mixed log function and gamma-type function with the observed lactation curve was almost of the same order. However, the gamma-type function gave a low peak yield, and therefore it is recommended that this function can give the best fit for low-yielding cows.
Keywords : Key words Fortnightly test day milk yields, gamma type function, quadratic model