Effects of cereal type and feed particle size on morphological characteristics, epithelial cell proliferation, and lectin binding patterns in the large intestine of pigs

The present study was undertaken to investigate the effects of cereal type and feed particle size on the morphological characteristics and epithelial cell proliferation of the large intestinal tissue in pigs. Forty pigs, weighing approximately 30 kg, were fed diets containing either coarsely or finely milled barley or wheat for a period of 4 wk. Tissue samples were taken from the cecum and from the proximal, medial, and distal colon at slaughter. The pigs fed the coarse diets had significantly larger crypts, in terms of height as well as volume, than did pigs fed the fine diets. The cereal type had no effect on the mucosal architecture. The epithelial cell proliferation, in terms of counted native mitoses in the crypts, was significantly higher in pigs fed the coarse barley diet than in pigs fed the coarse wheat diet or the fine diets. The volume of the mucin granules in the crypts constituted from 32 to 52% of the crypt volume and was greatest in the pigs fed the coarse diets. This effect of feed particle size was observed for neutral as well as for acidic mucins and sulfomucins. Lectin binding patterns indicated that more of the terminal sugars on glycoconjugates of the apical membrane on the mucosal surface were the sialic acid alpha-2,3 neuraminic acid, but less were mannose in the pigs fed the coarse barley diet. Distinct regional differences were observed among the intestinal sites. These included a decline in the epithelial cell proliferation and an increase in the volume of mucin in the crypts along the intestinal tract. Furthermore, the sialic acid alpha-2,3 neuraminic acid was more abundant in the medial colon than in the cecum; the contrary was seen for mannose and galactose. This study shows that the feed particle size of barley and wheat diets, more than the cereal type itself, affects the mucosal architecture, epithelial cell proliferation, and production and composition of the mucins in the large intestine of pigs. The study suggests that pigs fed a coarse diet are better protected against intestinal infections than pigs fed a fine diet.