Search

Six lactating Holstein cows (60-90 days) fed normal rations were bled via jugular catheters at 1130 (pre-milking), 1300 (post-milking), 1900, 2330 (pre-milking), 0100 (post-milking), and 0700 hr. Serum lipoproteins were isolated and fractionated by gel chromatography into three major fractions: very low density lipoprotein (VLDL), low density lipoprotein (LDL), and high density lipoprotein (HDL). VLDL protein content was high at both pre-milking times but decreased following milking. HDL protein showed an inverse relationship to that of VLDL, with peak HDL protein concentrations occurring after both milking times. Although no other dependent variables exhibited statistically significant time effects, mean VLDL triglyceride concentrations did decline after each milking time. The results suggested an increased rate of VLDL catabolism following milking.