Intestinal Absorption of Glucose and Amino Acids in Chickens Administered Monensin

Abstract

Effects of the ionophoric anticoccidial agent monensin on glucose and amino acid absorption were investigated in young broiler chicks. Chicks housed in cages with wire floors were fed a practical diet containing 0 or 121 ppm monensin for 2 to 3 weeks prior to measurement of nutrient absorption. Chicks were anesthetized with halothane, and the intestine was accessed through an incision in the abdominal wall. A 10-cm segment of the intestine immediately anterior to Meckel’s diverticulum was rinsed free of digesta and used for measurement of absorption in situ. One milliliter of saline solution containing 2 mM of glucose or a mixture of amino acids was injected into the lumen of the ligated segment, and recovery of glucose and amino acids in the lumen was determined after 4- and 5-min intervals, respectively. In one glucose study, the solution contained 0, 1, 10, or 80 μg/ml of monensin. In one amino acid study, the solution contained 0, 5, or 80 μg/ml of monensin; in subsequent studies, monensin was not included in the solution.Results show that neither dietary monensin nor monensin in the saline solution affected glucose absorption. Dietary monensin tended to depress lysine absorption but increased the absorption of tryptophan and arginine, the latter amino acid being markedly affected by monensin. Dietary monensin alone had no effect on absorption of cystine, isoleucine, methionine, or threonine. Inclusion of monensin in the saline solution depressed methionine absorption but only when birds also had been fed the diet containing monensin. Monensin in the saline solution depressed isoleucine absorption irrespective of dietary treatment. We conclude that monensin may cause subtle changes in amino acid transport in the gut or other tissues and suggest that this may be a factor in the depression of food intake and growth rate that occurs in uninfected chicks receiving dietary monensin.