The relationships between the fertility of dairy cows and clinical and biochemical measurements, with special reference to plasma glucose and milk acetone.

Blood and milk samples were taken at first insemination in 352 dairy cows from 18 herds for charting the relation between clinico-chemical parameters and fertility rate. Neither total protein, albumin, globulin, AST, bilirubin, bile acids, calcium, magnesium and phosphorus in blood nor urea in milk was significantly related to the rate of pregnancy. On the other hand, there was a significant difference for plasma glucose between cows that became pregnant and those that did not. Cows with low plasma glucose concentrations at first insemination also had low values four and seven weeks after calving, indicating that it is primarily cows with chronically low blood glucose which are likely to have reduced fertility. At first insemination there was no increase in the concentration of acetone in milk of cows with reduced fertility. However, they had had increased milk acetone concentrations three to five weeks after calving. It therefore seems possible to evaluate the risk of reduced fertility by measuring either blood glucose or milk acetone some weeks after calving. Owing to the difficulties associated with the sampling and laboratory techniques for glucose, analyses of milk acetone are more suitable under field conditions.