Utilization of amino acids administered enterally or parenterally to young pigs.

The utilization of essential amino acids provided enterally or parenterally was compared in six growing female pigs. Crystalline amino acids in aqueous solution were administered parenterally through a central venous cannula or enterally through a stomach fistula or in the diet. Other nutrients were provided in the diet. Plasma essential amino acid concentrations were not significantly different after the enteral and intravenous treatments in either the fasting or postprandial state except for phenylalanine and histidine for which both fasting and postprandial plasma concentrations were higher after intravenous infusion than after the enteral treatment. No significant differences were observed in plasma concentrations of dispensable amino acids. Urinary amino acid concentrations showed no treatment effects. Body weight gain and nitrogen retention during intravenous treatment equaled or exceeded the respective parameters during enternal administration. Serum biochemical parameters were unaffected by route of administration except for hematocrit and serum phosphorus concentrations which were significantly lower during intravenous infusion. Serum sodium and total protein concentrations were significantly higher during the oral casein treatment than after crystalline amino acids were presented by either route of administration. The data suggest that utilization of essential amino acids is similar whether they are given enterally or intravenously.