Journal of Applied Genetics 45(2), 2004, pp. 215-224

Milk trait heritability and correlation with heterozygosity in yak

X.P. JIANG, G.Q. LIU, C. WANG, Y.J. MAO, Y.Z. XIONG

Abstract: 382 yak cows were examined for milk yield, fat, protein and lactose contents. Six polymorphic loci, as1-CN, k-CN, b-CN, b-Lg, a-La and MUC-1, were scored by PAGE electrophoresis for each individual. The values of milk yield, fat, protein and lactose content were 247.13 kg, 5.81%, 5.18% and 4.93%, respectively. Based on the 6 polymorphism loci, the average heterozygosity of the yak population was 0.1794. Calculated by the marker-based method, heritability estimates for milk yield, fat, protein and lactose contents were 0.353 ± 0.093, 0.316 ± 0.101, 0.415 ± 0.098 and 0.481 ± 0.035, respectively. The relatively high or medium heritability of these traits indicate that it is feasible to rely directly on them in breeding for the improvement in a relatively short period. The significant linear regression between heterozygosity and fat percentage with a positive slope (R = 0.0420) indicated that inbreeding affected milk fat content in this population.

Key words: associative overdominance, heritability, milk trait, yak.

Correspondence: X.P. JIANG, College of Animal Science and Veterinary Medicine, Huazhong Agricultural University, Wuhan 430070, P.R. China, e-mail: xpjiang@mail.hzau.edu.cn