Liver Function in Dairy Cows at Parturition

Abstract

SUMMARY The possibility that subclinical liver damage may occur normally during late pregnancy and at parturition has been investigated in healthy dairy cows by measuring the plasma concentrations of the liver-specific enzyme G.D. and of G.O.T. and G.P.T., and also by measuring the rate of clearance of bromosulphthalein (B.S.P.) from the plasma approximately one week before, at, and one week after calving. Dimidium bromide, a known liver poison, was used to produce liver damage in one cow, and its effect on the same parameters have been studied. There were no significant changes in the concentration of G.D. during the 2 to 3 weeks spanning parturition, even though 3 cows showed evidence of milk fever, but there was a significant decrease in B.S.P. clearance one week after calving compared with the pre-calving levels. The mean values of k, the fractional clearance constant between 2 and 15 minutes after dosing, and kV, the plasma clearance before and after calving were −0·151 min.−1, and 6·74 l./min., and −0·121 min.−1 and 4·95 l./min. respectively. In contrast, a dose of dimidium bromide to one cow sufficient to cause a large rapid increase in the plasma concentration of G.D. 40 days after dosing did not produce any change in the liver’s capacity to clear B.S.P. from plasma at that time. It seems likely, therefore, that changes in liver function at calving in the cow are not degenerative in nature, but purely functional and related to the metabolic demands of lactation.