Determination of organic components of milk as method for evaluating energy status of dairy cows.

The objective of the investigations described in this work was to determine the energy status and to make recommendations for correcting the cow diet at a farm of high-yield dairy cows, on the grounds of values for the concentration of organic components of milk and their ratios in individual milk samples. A total of 147 cows were examined, including 97 in the first and 50 in the second lactation. Average concentrations of milk fat and urea were within the physiological values. Namely, the milk fat concentration in cows in the first lactation was 38.88?5.07 g/l, and it was 36.47?4.82 g/l in cows in the second lactation, while the urea concentration in cows in the first lactation 3.16?0.58 mmol/l and it was 3.72?0.64 mmol/l in cows in the second lactation. The protein concentration in both groups of cows was below the physiological values, being 30.33?2.35 g/l in cows in the first lactation and 30.17?2.27 g/l in cows in the second lactation. Based on the ratio of urea and protein concentrations, as well as of fat and proteins in the individual milk samples, it was concluded that in most examined cows, both in those in the first and those in the second lactation, there is a deficit of energy, along with a deficit or relative surplus of proteins. On the grounds of the obtained results, recommendations were given for correcting the feed rations in the coming period. .