Variation in the Concentration of Lipids and Some Other Constituents in the Blood Plasma of Cows at Various Stages of Lactation

Abstract

The variation in the concentration of protein, the various lipid fractions, volatile fatty acids, and glucose in plasma from the jugular vein was studied in 18 cows at different stages of lactation. The within-and between-cow values for the coefficients of variation and the results of the analysis of variance demonstrated that a large portion of the variation in the plasma concentration of triglycerides, free fatty acids, and glucose was due to diurnal variation within the individual cow. On the other hand the concentrations of protein, total fat, phospholipids, cholesterol esters, cholesterol, and ,B-carotene were relatively constant over a short period of time compared with the large variation between cows. The production of milk fat was positively correlated with the plasma concentration of total fat and cholesterol esters. The significance of these findings in relation to the contribution of the various plasma constituents to the synthesis of milk fat is discussed.