Lipoprotein composition of calves before and after weaning and comparison with adult cows.

Calves experience a significant decrease in dietary lipid intake with weaning. However, changes in lipoprotein metabolism during this period has not been described. Therefore, to evaluate changes in lipoprotein metabolism by weaning and age, differences in lipoprotein lipid concentrations and proportions were compared before and after weaning and between calves and adult cows. Blood samples were collected from 27 Holstein calves before (4 weeks old) and after weaning (13 weeks old). Blood samples were also collected from 10 adult cows (5 dry and 5 lactating cows). As the results, total lipid concentrations (triglycerides + total cholesterol + phospholipids) in low-density lipoprotein (LDL) and high-density lipoprotein (HDL) were higher for pre-weaning calves than those in post-weaning calves. However, there were no differences in lipid proportions contained in each fraction. Lipid concentrations were higher in adult cows than in calves for all fractions: very low-density lipoprotein (VLDL), LDL and HDL. The proportion of total cholesterol and phospholipids in the LDL fraction was higher in calves compared to adult cows and the proportion of lipids in the HDL fraction was higher in adult cows compared to calves. These results showed that weaning caused litte changes in lipid concentrations in each lipoprotein fraction, but that adult cows showed higher lipid concentration in VLDL, LDL, and HDL. In addition, more lipids were contained in HDL for adult cows than in calves.