Phenotypic and genetic analysis of milk β-hydroxybutyrate and fatty acid origin groups and production, reproductive, udder health, and longevity traits of Holsteins in Hokkaido, Japan

Abstract

We focused on milk β-hydroxybutyrate and fatty acid origin groups as metabolic indicator traits in Holsteins in Hokkaido, Japan, and we investigated the phenotypic and genetic relationships among the indicator traits and production (305-d milk, fat and protein yield), reproductive (days from calving to first service, days open and conception rate for first service), udder health (maximum somatic cell score within 305-d) and longevity (cow livability and stayability) traits. A least-squares analysis that included the indicator traits as explanatory variables revealed that production traits tended to decline with improvement in the indicator traits, whereas the other traits tended to improve. Heritability estimates for the indicator traits in a multiple-trait animal model were mostly between 0.2 and 0.3. The estimated genetic correlations suggest that genetic selection for the indicator traits causes favorable correlated responses of reproductive and udder health traits but unfavorable responses of production traits. Genetic selection for indicator traits may be possible but, in practice, antagonistic relationships between the indicator traits and production traits should be taken into account.