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 8 h 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 4 h 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 F AL. 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. © American Dairy Science Association, 2005.