Observation on plasma free amino acids of cow under different feeding.

The influence of nutritional alteration to the plasma amino acid patterns in cows was investigated. The ratio of the essential to nonessential amino acids (E/N) at 6 months after change of diet was higher in the group fed a high protein and low energy diet than the group fed a moderate protein and moderate energy diet (the control group). The total nonessential amino acid levels decreased in the former group. The decrease was due to lower values for glycine, alanine and glutamic acid.On the other hand, the E/N radio was lower in groups fed low protein diets than in the control group and total essential amino acid levels were lower in the former group than in the control group. The decrease was due to lower values for valine, threonine and arginine. Conversely, the higher values in glycine, serine and proline than those in the control group were observed.