Changes in milk ketone and fatty acid concentrations during early lactation in Holstein and Fleckvieh cows

The aim of this study was to compare the changes in milk composition postpartum, especially ketones and milk fatty acids (FAs), in Holstein and Fleckvieh cows kept under identical management conditions. Milk composite samples were collected from 66 cows during afternoon milking, at weekly intervals from one to eight weeks postpartum, and their components were determined by Fourier transform infrared spectroscopy. The Holstein cows had higher (P < 0.05) concentrations of long-chain FAs (ranging from 6% to 16% in different weeks), monounsaturated FAs (6% to 12%), and C18:1 (5% to 16%), as well as lower (P < 0.05) concentrations of saturated FAs (3% to 8%) and short-chain FAs (7% to 17%) in their milk than the Fleckvieh cows for almost the entire monitored period. These differences can be explained by pronounced lipomobilization, due to a negative energy balance, when mainly long-chain FAs from adipose tissue are incorporated into milk and significantly inhibit the de novo synthesis of FAs in the mammary gland. In conclusion, it can be assumed that breed-related metabolic changes during the first weeks of lactation have a large effect on the milk FA composition. This reflection of the metabolic load changes and lipomobilization in differing milk FA profiles would allow for the use of selected milk FAs to detect energy imbalances and their associated diseases in early lactation cows.