The coefficient of determination between NEFA and BHBA and the association between their ratio and the development of disease in healthy cows sampled during the post-partum period

As a consequence of lagging dry matter intake and increased energy demands, nonesterified fatty acid (NEFA) is released into the bloodstream from adipose tissue to be used as a source of energy in dairy cows in early lactation. Nonesterified fatty acid is used for milk fat synthesis, ketone production (e.g., -hydroxybutyrate; BHBA) and liver triglyceride accumulation. Nonesterified fatty acid and BHBA can be used as markers of negative energy balance (NEB) and elevated concentrations in the transition period have been associated with an increased risk of developing disease. The multiple pathways available for NEFA may result in a non-linear relationship between NEFA and BHBA concentrations. Additionally, the ratio between these two metabolites may differ in sub populations, e.g., subclinically ketotic (SCK) cows, and cows with elevated NEFA. Hence, the ratio of these metabolites may be a useful parameter for further understanding the biological mechanisms of adaption or maladaptation to NEB. The objectives of this study were to evaluate the R2 coefficient of determination between NEFA and BHBA in apparently healthy cows three to 14 DIM, and to estimate the association between the ratio of NEFA to BHBA and the subsequent development of displaced abomasum (DA), clinical ketosis (CK), or metritis (MET).