Metabolic biomarkers and milk production indicators associated with elevated non-esterified fatty acids in holstein dairy cows

Abstract

Abstract

Negative energy balance (NEB) is a common metabolic challenge during early lactation in dairy cows and is characterized by increased mobilization of body fat reserves and elevated circulating non-esterified fatty acids (NEFA). This observational study aimed to evaluate associations between serum NEFA concentration, milk production and composition traits, and blood biochemical indicators in early lactation Holstein dairy cows, and to assess the diagnostic performance of selected variables associated with elevated NEFA. A total of 182 multiparous Holstein cows between 4 and 30 days in milk were enrolled. Blood samples and milk production data were collected once from each cow on the same day during early lactation. Based on serum NEFA concentration, cows were classified into low-NEFA (≤ 0.56 mmol/L; n = 146) and high-NEFA (> 0.56 mmol/L; n = 36) groups. Cows with elevated NEFA concentrations showed significantly higher milk fat, fat-to-protein ratio (FPR), aspartate aminotransferase activity (AST), creatinine (CREA), sodium (Na), and chloride (Cl) concentrations, whereas magnesium (Mg), total protein (TP), urea, milk electrical conductivity, milk temperature, and gamma-glutamyl transferase (GGT) activity were lower ( p < 0.05). Spearman correlation analysis demonstrated positive associations between NEFA and milk fat, FPR, AST, CREA, and Na concentrations, and negative associations with Mg, urea, milk temperature, Ca, phosphorus (P), and GGT activity. Receiver operating characteristic (ROC) analysis indicated that milk fat, CREA, Na, FPR, Mg, and AST showed the greatest ability to discriminate cows with elevated NEFA concentrations. Elevated NEFA concentrations in early lactation dairy cows were associated with changes in milk composition, liver enzyme activity, electrolyte balance, and mineral metabolism. The combination of milk parameters obtained from automatic milking systems and selected blood biochemical indicators may improve identification of cows experiencing negative energy balance under commercial farm conditions.