Defined formula diets alter jejunal and colonic uptake of lipids in rabbits with intact intestinal tract and following ileal resection.

An in vitro technique was used to measure the jejunal and colonic uptake of fatty acids, decanol and cholesterol in sham-operated control (CONT) rabbits and in animals with a surgical resection of the distal half of the small intestine (RES). CONT and RES were fed standard Purina chow, Ensure, or Flexical HN for 2 weeks. The animals fed Ensure or Flexical HN consumed half the number of calories as the chow-fed rabbits and failed to gain weight. The mean of the jejunal dry weights were unchanged by diet or by ileal resection, although the height of the villi was lower in the animals fed the defined formula diets. Restricting chow intake to match the body weight gain of the animals fed Ensure or Flexical HN was associated with alterations in the uptake of lipids, but the pattern of changes was dissimilar to the pattern of changes observed in the resected animals or in the rabbits fed Ensure or Flexical HN. Ileal resection was associated with changes in the jejunal uptake of lipids and the influence of the defined formula diets on the uptake of short-, medium- and long-chain length fatty acids, decanol and cholesterol varied depending upon whether the animal had an intact intestinal tract or whether the animal had an ileal resection. It is concluded that the passive uptake of a homologous series of saturated fatty acids, cholesterol, and decanol into the jejunum and colon is modified by ad libitum feeding of Ensure or Flexical HN; the functional adaptation of the intestine and colon to dietary modification is influenced by the previous resection of the distal half of the small intestine; and these changes in the uptake of lipids are not explained solely by alterations in food intake, body weight gain, or intestinal morphology.