Risk factors associated with excessive negative energy balance in commercial United Kingdom dairy herds

This study assessed risk factors associated with excessive negative energy balance (eNEB) in UK dairy cows between April 2006 and March 2015. Blood samples were analysed for β-hydroxybutyrate (BHB), non-esterified fatty acids (NEFA) and glucose. Following removal of all potential duplicate cows, a final dataset of 69,161 unique individual cows was obtained including biochemical results, individual cow and feed data. Generalised linear mixed-effect models and multivariable classification tree-based models showed that individual cow risk factors for eNEB included: (1) days relative to predicted calving date (dry cows); (2) days in milk (lactating cows); (3) body condition score (BCS; lactating cows ≥ BCS 4; OR 2.1); (4) milk yield (around 40 L per day); (5) parity (first lactation heifers; odds ratio [OR] 0.46 compared to older cows during lactation); and (6) chronic inflammatory conditions as assessed by globulin concentrations ≥ 50 g/L (OR 0.79 for cows with evidence of chronic inflammation). There was a higher prevalence during April to October (OR 1.19), and the lowest prevalence was in November. Feeding grass silage and wholecrop (silage made from cereal crops) to dry cows was associated with a reduced prevalence of eNEB, whereas access to grazed grass was associated with a higher prevalence in both the dry period (OR 1.32) and lactation (OR 1.33). Knowledge of the risk factors associated with eNEB in commercial dairy herds assists in both the implementation of herd monitoring programs and reduction of eNEB in dairy herds, with associated reductions in the risk of periparturient diseases and improved dairy cow performance.