Association between the proportion of sampled transition cows with increased nonesterified fatty acids and β-hydroxybutyrate and disease incidence, pregnancy rate, and milk production at the herd level

In this study the herd alarm level was defined as the proportion of sampled transition cows per herd with increased prepartum nonesterified fatty acid (NEFA), postpartum β-hydroxybutyrate (BHBA), or NEFA concentrations that were associated with herd-level incidence of displaced abomasum (DA) or clinical ketosis (CK), pregnancy rate (PR), and milk production. The objectives were to 1) identify the herd alarm level for excessive negative energy balance and 2) describe the herd-level prevalence of this proportion. This was a prospective cohort study of 60 free-stall herds fed total mixed rations in the northeast United States. Two cohorts of approximately 15 animals were assessed for prepartum NEFA and postpartum BHBA and NEFA. The herd alarm level (i.e., the proportion of sampled animals above a certain metabolite threshold) was as follows: 15% had prepartum NEFA of 0.27 mEq/L; 15 and 20% had BHBA of 10 and 12 mg/dL, respectively; and 15% had postpartum NEFA of 0.60 and 0.70 mEq/L. The different herd alarm levels correspond to differences between the metabolites and respective herd-level effect. The herd-level effects for herds above the herd alarm level for prepartum NEFA were 3.6% increase in DA and CK incidence, 1.2% decrease in PR, and 282 kg decrease in average mature equivalent 305-d (ME 305) milk. For BHBA, the herd-level effects were a 1.8% increase in DA and CK, 0.8% decrease in PR, and 534 and 358 kg decrease in projected ME 305 milk yield for heifers and cows, respectively. For postpartum NEFA, the herd-level effects were 1.7% increase in DA and CK, 0.9% decrease in PR, and 288 and 593 kg decrease in projected ME 305 milk yield for heifers and cows, respectively. The prevalence of herds in which more than 15% of animals sampled had prepartum NEFA concentration ≥0.30 mEq/L was 75%, BHBA ≥12 mg/dL was 40%, and postpartum NEFA ≥0.70 mEq/L was 65%. This study showed that there were detrimental herd-level effects if a large enough proportion of cows had increased metabolite concentrations, and further demonstrated that a high prevalence of herds have opportunity for improvement.