Vacuolated Villous Epithelium of the Small Intestine of Young Pigs (with color plate I)

The villous epithelium of the small intestine from healthy pigs, killed during their first month of life, was examined. There were occasional vacuolated epithelial cells throughout the small intestine in most pigs; however, the occurrence of vacuolated epithelium (vacuolated epithelial cells in a continous layer along at least the distal 10% of all villi on the mesenteric side of a histological section) was related to area in the intestine and age of the pig. Ileal epithelium was vacuolated in nearly all pigs examined during their first 2 weeks of life; however, the frequency of vacuolated ileal epithelium was less in pigs examined during their third and still less in those examined during their fourth week of life. Jejunal epithelium was vacuolated less frequently than ileal epithelium and was not seen in pigs more than 11 days old. Vacuolated duodenal epithelium was not seen. Vacuolated ileal epithelium, in suckling pigs during their second week of life, was morphologically similar to that associated with absorption of colostrum in the neonate and took up bovine colostral whey pinocytotically. In contrast to unvacuolated epithelium, vacuolated epithelium stained supravitally with Evans blue dye given orally. Vacuolated ileal epithelial cells examined by autoradiography after exposure to tritiated thymidine had synthesized DNA more than 3 days previously. These observations were compared with reports that considered vacuolated epithelium, in 2 to 3-week-old pigs, to be pathologic. A hypothesis relating vacuolation to age of ileal cells was proposed.