利用Wood模型拟合中国荷斯坦牛乳脂率变化的效果分析

Fitting of Lactation Curves for Milk Fat Percentage for Chinese Holstein with Wood Model

为了解中国荷斯坦牛乳脂率变化规律,本文利用Wood模型对我国南方5个大中型奶牛场2008~2010年1~3胎中国荷斯坦牛33 194条测定日乳脂率进行曲线拟合。结果表明:中国荷斯坦牛乳脂率变化曲线为典型的倒抛物线形,第一胎拟合度最高(0.9820),第三胎最低(0.9789)。二胎牛乳脂率最先达到最低点(第16周),而三胎乳脂率最后达到(第19周)。就最低乳脂率而言,二胎牛最大(3.54%),而三胎牛最小(3.45%)。综合各方面情况得出,Wood模型适用于中国荷斯坦牛乳脂率变化的曲线拟合。

The objective of this study was to reveal the variation for milk fat percentage for Chinese Holstein. The curve of milk fat percentage was fitted by the Wood＇s incomplete gamma function model based on 33 194 test day DHI records from first lactation to third lactation for 5 dairy farms of Chinese Holstein form 2008 to 2010 in south of China. The results showed that the curve for milk fat percentage for Chinese Holstein was the typical inverted para-curve. By the fitness of curve, the first lactation was largest at 0.9820, and the third lactation was least at 0.9789. The week in lowest milk fat percentage for second lactation was most early （in the week of 16）, and most late for third lactation （in the week of 19）. In terms of lowest milk fat percentage, the second lactation was the largest at 3.54%, and the third lactation was the smallest at 3.45%. The Wood＇s incomplete gamma function model was aoorooriate to fit the variation for milk fat oercenta^e for Chinese Holstein based on all information in this study.