The effect of age and dietary protein sounce on free amino acids, ammonia, and urea in the blood plasma of the calf

Abstract

The concentrations of most of the free amino acids in the blood plasma of the calf decreased with increasing age between 3 days and 24 weeks. This effect was significant for serine, proline, methionine, leucine, glutamine, lysine, and histidine while the concentrations of aspartic acid, glutamic acid, valine, cystine, and ornithine remained constant.

Dried skim milk as a protein supplement in the calf's diet resulted in a higher concentration of free amino acids in the blood plasma than did meat meal. The relative proportions of the free amino acids in the plasma were related to their concentrations in the diet.

Addition of methionine to calf diets increased the free methionine concentration in the blood plasma.