Effects of Feeding Vitamin A and Lactoferrin on Epithelium of Lymphoid Tissues of Intestine of Neonatal Calves

Abstract

Circulating levels of vitamin A (retinol) and lactoferrin (Lf) are low in calves at birth. Bovine colostrum contains relatively high amounts of vitamin A and Lf, and both substances are intestinally absorbed by neonatal calves. There is evidence that these compounds interact with insulin-like growth factor binding proteins and thus influence the status and effects of insulin-like growth factor. The hypothesis was therefore tested that vitamin A and Lf influence epithelial growth, development, and absorptive capacity of the small and large intestine and modulate intestinal immune tissues (Peyer's patches; PP). Four groups of calves (n = 7 per group) were fed a milk-based formula with or without vitamin A and (or) Lf. Group F received formula (F) only; group FA was fed F supplemented with vitamin A; group FL was fed F supplemented with Lf, and group FAL received F plus vitamin A plus Lf. An additional group of calves (group C; n = 7) served as positive control and was fed colostrum (C) from pooled milk obtained on d 1, 2, and 3 of lactation. Amounts of nutritive components in formula and colostrum were similar. Blood samples were taken to measure vitamin A and Lf, and plasma xylose (added on d 4 to feeds) was measured postprandially for 8h as a marker of intestinal absorptive capacity. Plasma vitamin A was low at birth and further decreased in groups F and FL, but increased in groups FA, FAL, and C. Plasma Lf was low at birth and transiently increased up to 4h after the first meal in group C. Xylose absorption was higher in group C than in other groups. Incorporation of 5-bromo-2′-deoxyuridine into DNA (as a measure of cell proliferation rate) was enhanced in intestinal crypts in groups F and FL at all intestinal sites. Ileum villus heights of groups F and FL were smaller than of groups FA and FAL. Villus height to crypt depth ratios were smaller in F-fed groups (especially in groups F and FL) than in C-fed calves in the duodenum and jejunum. Incorporation of 5-bromo-2′-deoxyuridine into colon crypt cells of group F was greater than in groups FL and FA. Sizes of follicles of PP in the ileum were greater in group FA than in group F. In the ileum, vitamin A and Lf tended to interact with PP size. In conclusion, feed supplementation of vitamin A and Lf influenced growth of the ileum and colon. Interactions were observed between vitamin A and Lf on epithelial cell maturation, villus growth, and size of follicles in PP of neonatal calves.