Nearly identical oral and intravenous nutritional support in the rat: effects on growth and body composition

The physiological effects of administration of identical oral (amino acid diet) and intravenous (total parenteral nutrition) diets in the rat have not been examined. We designed a complete solid synthetic diet which is dissolved in water to produce nearly-identical liquid intravenous and solid oral diets. Minor differences in lipid and vitamin content were probably of little biological significance. The amino acid diet and total parenteral nutrition solution were compared in a 21-day trial with growing rats. Both groups of rats had similar weight gains. Total parenteral nutrition rats compared to the amino acid diet rats had significantly increased spleen and kidney weights; decreased stomach, small bowel, and testes weights; and unchanged heart, lung, liver, adrenal, and colon weights. Body composition studies suggested similar water and protein and increased fat accumulation by rats supported with the total parenteral nutrition solution when compared to rats fed the amino acid diet. These data indicate that the route of nutrient administration is an important determinant of nutritional result.