Abstract: [Objective] To characterize the growth and development laws of grazing Yunling goat kids during lactation period. [Method] A total of 36 Yunling goat kids including 17 male kids and 19 female kids produced by 24 nanny goats were chosen. During the 0 to 8 weeks of age, the kids were weighted once a week and the body size traits were measured once every other week. The growth curve fitting analysis on weights of male and female kids aged 0 to 8 weeks was conducted using three nonlinear models of Logistic, Gompertz and Von Bertalanffy, and the correlation analysis was carried out between birth weights and weights at the end of the experiment.[Result] The three used models all well fitted the growth curve of Yunling goat kids during lactation period with fitting degree greater than 0.99. The Gompertz and Von Bertalanffy models had better fitting performance. The inflection point times of the growth and development curve of male kids were 3.212 weeks and 2.862 weeks, and the weights at the inflection point were 5.691 kg and 5.352 kg, respectively; the inflection point times of that of female kids were 1.927 weeks and 1.325 weeks, and the weights at the inflection point were 4.532 kg and 3.960 kg, respectively. There were differences in weeks of age and weights in inflection point between male and female kids. The weight growth rate of male kids peaked at 3.037 weeks of age averagely, while that of female kids peaked at 1.626 weeks of age averagely. Birth weights of the kids had significant （P<0.01） effect on weights at the end of the experiment. [Conclusion] The results of this study provide references for scientific rearing of grazing Yunling goats and rational supplementary feeding of Yunling goat kids during lactation period.

Key words: Yunling goat, kids, growth curve fitting, correlation analysis