LAUSR

The aim of this paper was to examine the metabolic profile of the blood of cows of the Simmental breed during a production cycle, from two aspects: by season (spring, summer, autumn and winter), and by stages of production (1/3, 2/3, and 3/3 of lactation and the dry period). The cows were kept in an intensive system in tie-stall housing, and fed with complete diets, which differed in composition throughout the seasons and stages of production. Blood samples of 10 cows were taken four times during the production cycle (winter, spring, summer, and autumn) in the corresponding production stages (1/3, 2/3, 3/3 of lactation and dry period). They weretaken by puncture of the tail vein. The content of Ca, P, Mg, glucose, urea, total proteins, total cholesterol, AST, bilirubin, and the hormones thyroxine (T4), triiodothyronine (T3) and cortisol were determined in blood serum of cows. The results obtained from the F test indicated a statistically highly significant difference (P<0.01) in the contents of P, Mg, glucose, urea, cholesterol and thyroxine, depending on the season. Also, a statistically significant difference (P<0.05) was found in the content of AST and total proteins. The analysed parameters of the metabolic blood profile, tested with the F test, indicated that there was a statistically significant difference (P<0.05) in Mg content depending on production stages.