Relationships Between Contents of Biochemical Metabolites in Blood and Milk in Dairy Cows During Transition and Mid Lactation

摘要

The objective of this study was to determine blood and milk metabolites and their interrelationships to evaluate the metabolic status in dairy cows for early diagnosis of subclinical metabolic disease at different stages of lactation. For this study,blood and milk samples were taken from 36 Holstein dairy cows during morning milking. The cows were divided into three groups according to the nroduction period.Group 1 consisted of cows in late pregnancy (n = 12)Group 2 comprised early lactation cows (n=12)Group 3 included mid-lactation cows (n=12).From late pregnant (Group 1) cows' nilk samples were collected after calving. The concentrations of glucose, triglycerides TG), total cholesterol (TChol), total protein [TP), albumin, urea, calcium (Ca), magnesium (Mg) and inorganic phosphorus (iP), andactivities of aspartate aminotransferase (AST), alanine aminotransferase (ALT), andalkaline phosphatase (ALP) in the blood and the contents of fat, protein, urea, Ca, iP, Mg, and activities of AST, ALT and ALP in milk were determined. Statistically significant differences (P < 0.05) were observed in blood TG, TChol, urea, AST, ALT, andALP levels and milk fat and urea concentrations among experimental groups of cows. Significantly negative correlations (P < 0.05) were found between TG in blood and fat (r=-0.525) and urea (r=-0.711) in milk; and between TP in blood and urea in milk (r=-0.366). Significantly positive correlations (P < 0.05) were observed among TG in blood and Ca (r=0.403), Mg (r=0.430), iP (r=0.353), protein (r=0.381) and ALT (r=0.508) in milk; TChol in blood and fat (r=-0.362) in milk; albumin in blood and ALT (r=0.390) in milk; activity of AST in blood and fat ( r=0.429) and urea (r=0.455) in milk. Based on changes in blood and milk metabolites at different stages of lactation, the present results suggested that early lactation cows showed a mild degree of hepatic lesions, probably due to fat infiltration. The results showed that changes in blood and milk metabolite levels and their interrelationships can be helpful in the herd monitoring of metabolic status in dairy cows and for the early diagnosis of subclinicalmetabolic disease.