CHANGES IN MILK FATTY ACID COMPOSITION IN RELATION TO INDICATORS OF ENERGY BALANCE IN HOLSTEIN COWS

The contents of protein (P), fat (F), a F:P ratio, and content of individual fatty acids (FA) and groups of FA, including ratio of SFA:UFA (saturated FA-to-unsaturated FA) and MUFA:PUFA (ratio monounsaturated FA-to-polyunsaturated FA) in milk during the fi rst 17 weeks of lactation with respect to the development of NEB demonstrated by the change in cows’ body condition. The diff erences in fat content were more pronounced than those in protein content. The resulting changes of the fat-to-protein ratio over time are associated with adipose tissue mobilization due to NEB, which was also confi rmed by the changes in the BCS during the experimental period. The results indicate the possibility of using both fat content and fat-to-protein ratio as indicators of NEB in early lactation cows. The highest concentrations of saturated FA (SFA) were observed for C14:0, C16:0, C18:0, and also for the SFA with low carbon numbers. The highest concentrations of unsaturated FA (UFA) were determined for C18:1, C18:2, and C16:1. The signifi cant diff erence in SFA:UFA between cows with decreasing of the BCS and cows without big change in the BCS a er calving were not found. The changes in MUFA:PUFA in milk during the fi rst 5 weeks of lactation diff ered between the cows with low and high decrease of BCS one month a er calving. In cows with a greater NEB eff ect was observed ratio of PUFA:MUFA in milk with a value above 6.5. The results suggest the possibility of using MUFA:PUFA ratios as suitable indicators of NEB in cows a er calving.