The effect of diarrhea on the oxidation of 14C-phenylalanine in piglets receiving diets varying in protein and proline concentration.

The oxidation rate of L-[1-14C]phenylalanine in piglets suffering from diarrhea and receiving diets varying in concentration of protein or proline was compared to the oxidation rates in healthy animals. Phenylalanine oxidation was used to indicate the partition of absorbed amino acids between protein synthesis and oxidation. Piglets receiving adequate protein diets and suffering from diarrhea oxidized significantly more phenylalanine (P less than 0.001) than healthy piglets. Piglets receiving additional proline and with symptoms of diarrhea oxidized phenylalanine at rates 50 to 70% higher than healthy piglets. The results show that piglets with diarrhea are less able to retain absorbed amino acids for protein synthesis than healthy pigs. The reduced nitrogen retention commonly observed in animals with diarrhea may be partly explained by the increased catabolism of absorbed amino acids.