ORGANIC MILK INGREDIENTS AS AN INDICATOR OF ENERGY STATUS OF COWS WITH DIFFERENT MILK PRODUCTION DURING THE FIRST 100 DAYS OF LACTATION

The aim of the study was to evaluate energy status of cows with different milk production during the first 100 days of lactation, based on the concentration of organic milk ingredients and ratio of urea and protein. The study included a total of 174 Holstein cows, divided into three groups based on daily milk yield (group A, n=15, bellow 20 litters, group B, n=64, from 20 to 30 litters, group C, n=95, above 30 litters). All cows were kept under usual farm conditions and fed diets adjusted to production category and period of the year. The concentration of milk fat declined with increasing daily milk production, while the concentration of urea had opposite trend. The concentrations of lactose and protein were the highest in the group B, while groups A and C had similar values. Statistically significant differences between all tested groups were found in concentrations of milk fat (4.28±0.56 versus 3.95±0.51 and 3.62±0.47 %, respectively), urea (2.81±0.32 versus 3.03±0.52, and 3.76±0.56 mmol/l, respectively), as well as the values of the concentrations of lactose and proteins between groups B and C (4.79±0.14 versus 4.73±0.13, and 3.10±0.21 versus 3.01±0.24 %). The distribution of values for the tested parameters within charts showing the relationships between urea and protein indicates a more or less pronounced energy deficit and the deficit or relative surplus of dietary protein in most of the cattle, which adversely affects their daily milk production and health.