Exploring the role of milk yield in the first week of lactation on the association between hyperketonemia and reproductive performance in dairy cattle

Summary: Hyperketonemia (HYK) is a metabolic disorder in dairy cattle related to difficulties during the transition period and associated with suboptimal reproductive performance. Studies have proposed the monitoring of the transition period based on early-lactation milk yield. Therefore, our objective was to explore the role of milk yield during the first week of lactation on the relationship between HYK and reproductive performance. Cows (N = 2,091) were tested for HYK (blood BHB ≥1.2 mmol/L), between 3 and 10 DIM. First-week milk yield was classified into 3 levels according to parity and herd. Reproductive performance was assessed until 150 DIM. After adjustments, we found no evidence to support an association between HYK and reproduction. However, models stratified by early milk yield showed that HYK was associated with lower risk of pregnancy among low-yielding cows. Results suggests that early milk yield plays a role in the association of hyperketonemia with reproduction.