Genetic parameters analysis of conformation traits and milk production traits in Chinese Holsteins

Abstract Background: The objective of this study was to explore the genetic parameters of conformation traits and milk production traits of Chinese Holstein cattles in Northwest China, and to provide a reference for dairy cattle breeding in this region. The phenotypic data of 23 conformation traits and 5 milk production traits of 7,930 Chinese Holsteins from 18 pastures from 2007 to 2020 were collected. With field, identification season, calving season, and appraiser effect as a fixed effect and individual additive genetic effect as a random effect, DMU package and AIREML combined with EM algorithm were used to estimate the genetic parameters of conformation traits and milk production traits. Results: The estimated heritability of conformation traits ranged from 0.11 (angularity) to 0.37 (heel dept), and the genetic correlation between conformation traits ranged from -0.73 (bone quality and rear leg-rear view) to 0.76 (chest width and loin strength). The estimated values of genetic correlation between conformation traits and milk production traits ranged from -0.31 (pin setting and milk yield) to 0.34 (stature and milk yield), -0.33 (pin setting and 305-d fat) to 0.57 (breast texture and 305-d fat), -0.32 (pin setting and 305-d protein) to 0.38 (udder texture and 305-d protein), and -0.43, respectively (heel dept and somatic cell score) ~ 0.34 (body depth and somatic cell score) and -0.56 (foot angle and 305-d milk yield) ~ 0.32 (body depth and 305-d milk yield). There was a positive genetic correlation between most conformation traits and 305-d fat and 305-d protein, but a weak genetic negative correlation with milk yield. Conclusions: Strengthening the selection of medium and high heritability of milk production traits and conformation traits, especially the selection of rear udder traits and body shape total score, was beneficial to improve the performance of dairy cows.