Abstract: The objective of this study was to develop a set of technique for culling female yaks fattening and yak calves rearing under semi-confined condition. A total of 66 lactational female yaks and 66 male yak calves were selected and randomly divided into experimental group and control group, respectively. During the yak calves rearing period （from December 4, 2017 to March 5, 2018）, the female yaks of the experimental group received supplementary feeding. The yak calves of the experimental group received milk from the female yaks of the experimental group before weaning （on March 5，2018） and simultaneously received supplementary feeding. The female yaks of the control group received no supplementary feeding and were kept in the conventional grazing mode. The yak calves of the control group were weaned on December 4, 2017 and received supplementary feeding. During the fattening period （from March 5, 2018 to slaughter）, the female yaks of the experimental group received supplementary feeding and were slaughtered in June （non-peak time for yak slaughter）; the female yaks of the control group received no supplementary feeding and were slaughtered in September or October （peak time for yak slaughter）. During the yak calves rearing period, the body weight of the female yaks of the experimental group was observed and recorded. The body weight and body size indicators of the two groups of yak calves were measured on the 4th of each month, and statistical analysis was performed. The fattening profit of the female yaks of the experimental group in non-peak time for slaughter was calculated. The results showed that during the yak calves rearing period, the weight of the individual female yak of the experimental group was 1.17 kg reduced due to the lactation for the yak calves of the experimental group. On January 4, 2018, the weight of the yak calves of the experimental group was extremely significantly higher （P<0.01） than that of the control group, and the body length and chest circumference were significantly higher （P<0.05） than of the control group; on February 4 and March 4, 2018, the yak calves of the experimental group had extremely significantly higher （P<0.01） body weight, body height, body length and chest circumference compared to that of the control group. The fattening profit of the female yaks of the experimental group in non-peak time for slaughter was 1 063.05 Yuan. Our results provide technical support for improving the fattening profit of culling female yaks and the rearing quality of yak calves under semi-confined condition.

Key words: culling female yaks, yak calves, fattening, rearing, slaughter in non-peak time