Optimal Dietary True Ileal Digestible Threonine for Supporting the Mucosal Barrier in Small Intestine of Weanling Pigs1–3

Abstract

Threonine is of great importance for the maintenance of intestinal health. However, little is known about the optimal level of dietary threonine for neonates or the underlying mechanisms of its beneficial action. Our objective in this study was to determine the effects of graded levels of true ileal digestible (TID) threonine on the intestinal mucosal barrier in weanling pigs. Four groups of piglets (n = 8/group) were fed for 14 d diets containing 0.37, 0.74, 0.89, or 1.11% TID threonine. The duodenal mucosa of piglets fed the 0.37 and 1.11% TID threonine diets exhibited distorted villus architecture. Compared with pigs fed the 0.74 and 0.89% TID threonine diets, apoptosis was higher (P < 0.05) in pigs fed the 1.11% TID threonine diet. Feeding 0.37 and 1.11% TID threonine reduced (P < 0.05) concentrations of ileal acidomucins and duodenal sulfomucins, respectively, compared with the 0.74% TID threonine group. Compared with piglets fed the 0.89% TID threonine diet, the total amounts of mucins in duodenum, as well as expression of MUC2 mRNA in duodenum and jejunum, were reduced (P < 0.05) in piglets fed the 0.37 and 1.11% TID threonine diets. Collectively, these findings indicate that a deficiency or excess of dietary threonine affects the intestinal mucosal barrier and that the optimal level of dietary TID threonine for supporting gut barrier function is 0.89% for weanling pigs. These new findings have important implications for both the maintenance of normal physiological functions and the prevention of gut-related diseases in neonates.