Plasma Glutamic-Oxaloacetic and Glutamic-Pyruvic Transaminase Activities in Holstein Cattle. I. Effects of Stage of Lactation, Gestation, and Level of Milk Production

Abstract

A total of 748 jugular vein plasma samples was taken from 69 Holstein cows sampled monthly throughout one lactation and the corresponding gestation period. Glutamic-oxaloacetic transaminase activity varied significantly (P<0.01) between the seven, 60-day stages of lactation and also showed a significant (P<0.01) linear relationship, with the highest activity in the first stage, and lowest in the dry cows (52.57 and 31.59 Karmen units, respectively). Glutamic-pyruvic transaminase activity also varied significantly (P<0.01) between the stages of lactation and showed significant linear (P<0.01), quadratic (P<0.01), and cubic (P<0.05) relationships. The variations in enzyme activity among the 11, 30-day stages of gestation were not significant, but a significant (P<0.05) linear relationship was observed for glutamic-oxaloacetic transaminase. A regression analysis indicated that milk production was linearly, but negatively, related (P<0.01) to glutamic-oxaloacetic transaminase activity, whereas glutamic-pyruvic transaminase was related in a quadratic manner (P<0.05).