Hu, X. F., Guo, Y. M., Li, J. H., Yan, G. L., Bun, S. and Huang, B. Y. 2011. Effects of an early lipopolysaccharide challenge on growth and small intestinal structure and function of broiler chickens. Can. J. Anim. Sci. 91: 379–384. Two experiments were conducted to determine the effect of early exposure to lipopolysaccharide (LPS) on small intestinal structure and function of broiler chickens. Seven-day-old birds were randomly allotted to two equal treatments: an LPS-injected treatment in which the birds were injected intraperitoneally with LPS 500 µg kg−1 body weight (dissolved in 1 mL saline) on 8, 10, 12, 15, 17, and 19 d of age, i.e., on days 1, 3, and 5 d for 2 continuous weeks, and a control treatment (CTRL) in which the birds were similarly injected with 1 mL saline as a placebo. In exp. 1, food intake and weight gain were monitored over the 2 wk, the weight of the small bowel was determined at 14 and 21 d of age and duodenal and jejunal villus height and crypt depth, D-xylose uptake were also measured at 21 d. In exp. 2, additional measurements of the intestinal peristalsis ratio and the BrdU-labeling index and duodenal sodium-glucose co-transporter-1 (SGLT1) mRNA level were made at 21 d of age. The results showed that LPS challenge decreased feed intake, daily gain, duodenal and jejunal villus height and crypt depth, plasma D-xylose concentration and intestinal BrdUrd-labeling index, respectively (P<0.05) as well as small bowel weight at 14 and 21 d of age (P<0.05). Conversely, LPS injection increased SGLT1 mRNA level in the small intestine (P<0.05) and the small intestinal relative weight at 14 (P<0.05) and 21 d of age (P=0.063). Following LPS injection there were non-significant changes in feed conversion ratio and intestinal peristalsis ratio (P>0.05). In conclusion, early LPS challenge delayed the growth of intestine and impaired small intestinal structure and absorptive function.