RELATIONSHIPS BETWEEN SERUM ENZYME ACTIVITES IN THE MILK AND BLOOD IN DAIRY COWS DURING DIFFERENT STAGE OF LACTATION PERIOD

This study aimed to determine blood and milk enzyme activites as indicators of liver function and their correlations in dairy cows during different stage of lactation period. Blood and milk samples were collected from 100 Holstein dairy cows during morning milking. The cows were allocated to four groups according to the production period, including cows in early (n = 18), full (n = 26), mid (n = 25) and late (n = 31) lactation. The value of serum enzyme activites of aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), gamma-glutamyl transferase (GGT), and lactate dexydrogenase (LDH) in the blood and milk were determined. The activities of blood and milk serum AST, ALT, ALP and LDH were significantly higher (P< 0.01) in early and full lactation cows than in the other two groups of cows, suggesting mild fat infiltration of liver cells. The enzyme activities in milk were positively correlated with those in the blood (P< 0.01). In conclusion, similar changes in blood and milk serum enzyme activites during lactation and milk to blood correlations confirm that milk has great potential in predicting of blood metabolites and metabolic status of cows.