Abstract:

【Objective】 In order to meet the precise prediction of nutrient requirements for dairy cattle individuals and investigate the secreting pattern of milk composition. 【Method】 One hundred and ninety-six cows were divided into 7 groups according to 305-day yield in the third parity from 5000 to 11999 kg with an interval of 1000 kg. The adjusted month-milk-yields were fitted using 3 equations (Wood, Gompertz and Dijkstra equations). Twenty-one sets of lactation curve models for different milk yield ranges were obtained by nonlinear parameter estimation and mean square error (MSE) analysis and lactation features of each yield range including initial yield (y0), time to peak yield (tm), peak yield (ym) and relative rate of decline at the point halfway between peak yield and end of lactation (r(th)) were revealed by model parameters. 【Result】 Analysis on the model parameters and feature indices showed that the above three mathematic equations were all able to describe lactation characteristics of Chinese Holstein dairy cows among different milk yield ranges for the third parity well. The parameter estimation for both Wood and Gompertz equations (empirical model) with three parameters was more simple and practical than for Dijkstra equation (mechanical model) with four parameters, and the former model parameters and lactation characteristics demonstrated by them were better than the later. 【Conclusion】The above lactation curve models for different milking ranges established for different milking ranges could provide a helpful basic model for the accurate prediction of nutrient requirements and precise feeding for dairy cattle.

Key words: China Holstein dairy cattle, lactation range, lactation curve, model