Plasma total protein measurement for prediction of disease and mortality in calves.

Plasma concentration of total protein (TP) was measured by refractometer in 76 calves, 1 to 8 days of age, on 3 farms. Three calves died before weaning at 5 weeks; all had plasma TP less than 6 g/dl. The frequency of disease before weaning was 17/29 (59%) in calves that had plasma TP of less than or equal to 6 g/dl, and this was significantly (P less than 0.001) less than the disease frequency of 9/47 (19%) in those with higher values of plasma TP. For 9 calves, plasma TP content was 4.72 +/- 0.22 (mean +/- SD) before ingestion of colostrum. The increment of plasma TP after colostrum feeding was 2.03 +/- 0.61 mg/dl (P less than 0.001). Plasma TP was as useful as serum zinc sulfate turbidity test results or total immunoglobins (as measured by radial immunodiffusion) in predicting disease susceptibility during the first 5 weeks of life, based on determinations made in 32 calves during the first 8 days of life. It was concluded that determination of plasma TP is the most convenient method of evaluating the immune status of calves under field conditions.