Variations in blood composition in dairy cows during pregnancy and after calving.

The effects of pregnancy and of the onset of lactation on blood composition was studied in 21 Friesian cows. Among the 23 components studied only seven showed significant variations. Serum iron decreased at the end of pregnancy while creatinine increased throughout the last six months. There were decreases in blood glucose, cholesterol and alanine aminotransferase at the end of pregnancy. Triglycerides increased rapidly after drying-off and serum urea increased in the first month after calving.