Abstract: Two years of study on the effect of grazing intensity on yaks’ growth indicates that in the winter pastureland the regression value of grazing intensity on a yak’s weight gain is linear,while in the summer pastureland,a second degree polynomial regression is seen.Under different states of grazind intensity,the regerssion value of a yak’s weight,and daily weight gain,with change of time,is linear,or a 5th or 6th degree polynomial.During the period of the study,the reagession value of a yak’s weight gain,live weight gain per hectare,on grazing intensity is obviously linear.A variance analysis indicates that among the 3 treatments the average total weight gain of a yak varies significantly (F=5.03>F_0.05=3.68).By SRR analysis,slight difference exists between light and moderate grazing,though remarkable variance shows between the former two and geavy grazing.

Key words: Grazing intersity, Growth of yaks

摘要： 两年的试验结果表明,牦牛在冬季个体增重与放牧强度呈显著的线性回归关系,但夏季则呈极显著的二次多项式回归关系。在不同放牧强度下,牦牛体重、日增重随着时间的变化分别呈极显著线性回归和高次多项式回归关系;在试验期间,牦牛的增重、每公顷增重与放牧强度均呈明显的线性回归关系。方差分析结果表明,处理间牦牛平均总增重差异显著(F=5.03>_0.05=3.68),新复极差测验结果表明,轻度放牧和中度放牧之间差异不显著,但二者和重度放牧间差异显著。

关键词: 放牧强度, 牦牛生长