Phenotypic association between energy balance indicators and reproductive performance in primiparous Holstein cows.

Energy balance was assessed during the first 13 weeks postpartum in 497 primiparous Holstein cows and the relationship with reproductive performance was investigated. A significant association was observed between body condition score (BCS) and a number of reproductive traits, including conception at first artificial insemination (AI), number of inseminations per conception, calving to conception and calving intervals, percentage pregnant by the end of a 305-day lactation and incidence of metritis. The BCS from calving to week 9 (before the first AI) appeared to adequately predict future reproductive performance as it was correlated with calving interval, conception at first AI, metritis and percentage pregnant by the end of a 305-day lactation. Plasma β-hydroxybutyrate (BHB) concentrations were correlated with the latter trait only, whereas non-esterified fatty acid concentrations were not associated with reproductive performance.