INTERNAL MILIEAU OF DAIRY COWS AT THE BEGINNING OF LACTATION AND ITS INFLUENCE ON COMPOSITION OF RAW MILK

Abstract

The aim of this work was to evaluate selected blood biochemical parameters and milk composition of dairy cows at the beginning of lactation and to observe the correlations between blood and milk parameters. In total, 15 Holstein cows at the beginning of lactation were chosen. Blood and milk samples were collected. Energetic (glucose - GLU, d-beta-hydroxybutyrate - D-BHB, triglycerides - TG), nitrogenous (total proteins - TP, UREA), hepatic (aspartate aminotransferase - AST, alanine aminotransferase - ALT, gamma-glutamyltransferase - GGT, alkaline phosphatase - ALP, bilirubin - BILI, cholesterol - CHOL) and mineral (sodium - Na, potassium - K, chlorides - Cl-, calcium – Ca, phosphorus – P, magnesium - Mg) profiles were determined in the blood serum. Levels of lactose, fat, proteins and minerals (sodium - Na, potassium – K, calcium – Ca, phosphorus – P, magnesium - Mg) were determined in milk. Most of the parameters outside physiological limits were found among mineral and hepatic profile. Levels of calcium, phosphorus and sodium were decreased in comparison to reference values. Average concentration of urea was also lower. On the other hand, increase of aspartate aminotransferase and gamma-glutamyltransferase were observed. Levels of lactose (4.82 g.100g-1), fat (4.21 g.100g-1), protein (3.14 g.100g-1) and calcium (4.82 g.l-1) in milk complied with Slovak national standard (STN 57 0529). In our study, ratio of fat to protein lower than 0.75 was observed in 13 % of cows (risk of ketosis) and higher than 1.4 in 40 % (NEB). Strong negative correlation between serum cholesterol and milk fat (-0.716; P<0.01) and middle strong negative correlation between cholesterol and milk protein (-0.397; P<0.01) were observed.
ALT affected negatively amount of phosphorus in milk (-0.417; P<0.001), which complied with demineralization of the organism and following restriction of liver detoxification activity. On the other hand, strong positive correlation was observed between serum ALT and milk sodium (0.738; P<0.05), what points to close relationship between hepatic enzymes and mineral composition of raw milk.