title: Description and validation of an in situ autoperfusion method to determine nutrient absorption and metabolism in bovine small intestine.
abstract: Holstein bull calves, 8 to 12 wk of age, were anesthetized with halothane gas. An approximate 20-cm section of small intestine, 60 to 90 cm proximal to the ileocecal junction was clamped to isolate blood circulation to a single set of arcuate vessels and to form an intestinal segment fitted for infusion and drainage. The vein was catheterized to allow total venous collection. Donor blood was transfused via jugular vein to replace venous drainage. This technique was evaluated in four calves by exposing the lumen to eight replications (12 or 20 min incubation, 30-min wash with 39 C saline) of 16 mM L-Met (14C-labeled). Time course appearance of Met in venous blood indicated similar rates and patterns of absorption for individual calves. There were no clinically significant alterations in jugular blood chemistry profiles across replications. Four calves were used to evaluate the effect of three isotonic perfusion media (saline, Krebs-Ringer bicarbonate and M-199 tissue culture media) on Lys and Met absorption. Venous flow rates and absorption of Lys were faster with Krebs buffer than with other media. Perfusate medium did not influence venous flow rates or absorption of Met. Effect of restricting venous flow on absorption of Lys and Met was evaluated in two calves. Flow was alternately controlled (6.5 ml/min) or allowed to flow freely (mean = 12.2 ml/min). Restricting flow decreased steady-state absorption. Light and scanning microscopy indicated maintenance of mucosal tissue integrity throughout 8 h of anesthesia. Results demonstrate validity of the in situ technique to study nutrient absorption in the young bovine.
mesh_terms: D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D002417:Cattle / Q000378:metabolism*; D007408:Intestinal Absorption; D007421:Intestine, Small / Q000033:anatomy & histology / Q000502:physiology*; D008239:Lysine / Q000378:metabolism; D008297:Male; D008715:Methionine / Q000378:metabolism; D010477:Perfusion / Q000379:methods / Q000662:veterinary*
chemical_list: D008715:Methionine; D008239:Lysine