Selection of an intact casein or casein hydrolysate diet by rats submitted to protein deprivation and bowel resection.

The feeding preference of normal rats (n = 14), malnourished rats (n = 14), and enterectomized rats (n = 16) was determined in a situation of free choice of three complete solid diets which only differed in extent of protein polymerization: intact casein, casein hydrolysate, and an amino acid mixture with a composition similar to that of casein. The animals were housed in metabolic cages for 30 days and allowed to freely choose among the three diets presented simultaneously. All three groups showed an initial preference for the intact casein diet. The control group maintained this preference, whereas the malnourished and enterectomized groups reduced the ingestion of the intact casein diet and increased the ingestion of the amino acid diet. The nitrogen balance, which was always positive in all three groups, was constant in the control group (1.51 +/- 0.26 g) initially higher (1.77 +/- 0.19 g) in the malnourished group, with a subsequent fall (1.13 +/- 0.24 g), and lower in the enterectomized group (0.83 +/- 0.32 g). Although total intake was similar for the control and malnourished groups, the malnourished group presented a higher weight recovery (130.2%). In contrast, the food intake of the enterectomized group was much lower, with a small weight gain. After treatment that impairs the digestive tract, intact casein was the initially preferred nitrogen source, which later tended to be replaced with free amino acids. This change was accompanied by an improvement in nitrogen balance and body weight, especially after protein malnutrition. These data may suggest that, in clinical practice, the use of enteral diets containing fully hydrolyzed protein may be of benefit in terms of the recovery of malnourished patients and of patients with short bowel syndrome.