Utilization of nutrients by the small intestine of the developing pig and role of corticosteroids in postweaning lag in pigs

Abstract

The present study analyzed the effects of weaning-related stress and the consequent endocrine production on the integrity and absorptive characteristics of the epithelium of the small intestine. In Exp. I and Exp. 2, the pattern of cortisol secretion after weaning was determined in 93 piglets weaned at 21 or 28 d of age. Regardless of the weaning age, cortisol concentration showed a similar pattern in plasma after weaning. A one to two-fold increase in cortisol was observed 24 h after weaning followed by a gradual return to preweaning levels 1 1 to 15 d after weaning. In Exp. 3, the administration of different doses of dexamethasone (0, .2,.4, and .6 mg/kg ) on the performance of pigs at the time of weaning (28 d of age) was evaluated for 4 wk. Average daily gain, ADFI, and G/F were not affected by dexamethasone, regardless of the dose. However, larger doses of the glucocorticoid trended to reduce production efficiency of the pigs. In Exp. 4, substrate utilization by cells of the small intestine was determined by cannulating the ileal artery and vein and determining the disappearance and production of metabolites from the small intestine. Preweaned (14 and 21 d of age), and postweaned (28 and 56 d of age) pigs were used. The nursing pig's intestine used both glucose and glutamine as energy sources, but after weaning, glutamine utilization increased. The final two experiments examined the effects of supplemental glutamine (I%) and glucose (I. 12%) in the water of weaned pigs and the effect of dexamethasone injection at weaning on intestinal morphology and absorptive ability, as measured by the xylose test. Crypt depth in the duodenum of pigs supplemented with glutamine were similar to those suckling piglets, but jejunal villus height and crypt depth, and xylose absorption were not affected by any of the treatments. These results show that weaning produced an endocrine response characterized for a large production and release of cortisol. Glucose and glutaniine were found to be the fuel substrates of choice by the cells of the small intestine of the nursing and weaned pig. However, their inclusion in drinking water after weaning did not alter morphology or absorptive ability of the small intestine suggesting that the dietary content may have been adequate. Altering glucocorticoid status by injection of dexamethasone had no measurable effect on performance or intestinal function of the weaned pig.