Association of Metabolic Disease Occurrence on Milk Fatty Acid Composition and Rumination Time in Early Lactation Dairy Cows and Evaluation of Their Potential as Diagnostic Indicators.

This study investigated the relationship between metabolic disease, milk fatty acid composition, and rumination time in early lactation dairy cows and evaluated their utility as diagnostic indicators. Twenty-two Holstein dairy cows were monitored for 8 weeks postpartum, with weekly milk and blood sampling and continuous rumination monitoring. Thirteen cows developed subclinical or clinical metabolic disease. Compared to the healthy group, the disease group showed significantly lower de novo fatty acids (p < 0.01) and higher preformed fatty acids (p < 0.05) as a percentage of total milk fatty acids. De novo fatty acid content per unit of milk (g/100 g milk) tended to be lower in the disease group (p < 0.10). Lying rumination time also tended to be lower in the disease group (p < 0.10). Receiver operating characteristic analysis showed that de novo fatty acids, preformed fatty acids, and lying rumination time demonstrated higher diagnostic accuracy than serum nonesterified fatty acids. These results suggest that milk fatty acid composition and rumination behavior are useful screening tools for detecting metabolic diseases in early lactation dairy cows.