Protective effects of carnosic acid on growth performance, intestinal barrier, and cecal microbiota in yellow-feathered broilers under lipopolysaccharide challenge.

This research was performed to investigate protective effects of carnosic acid on growth performance, intestinal barrier, and cecal microbiota of lipopolysaccharide-challenged broilers. Three hundred 1-day-old yellow-feathered broilers (male) were allocated randomly into 5 treatments, with 6 replicates per treatment, and 10 birds per replicate cage. Birds in both the control group (CON) and the lipopolysaccharide-challenged group were provided with a basal diet, while others were fed a basal diet supplemented with 20, 40, and 60 mg/kg carnosic acid (CA20, CA40, CA60), respectively. At 17, 19, and 21 days of age, birds were injected intraperitoneally with lipopolysaccharide (500 μg/kg body weight), except those in CON, which were injected with saline. Compared with challenged birds, the CA20, CA40, and CA60 increased (P < 0.05) the final body weight, average daily gain, and average daily feed intake, and the CA40 and CA60 also decreased diarrhea rate. Compared with challenged birds, carnosic acid reduced (P < 0.05) plasmal levels of D-lactic acid and endotoxin, increased (P < 0.05) the villus height to crypt depth ratio, and the number of goblet cells in duodenum. The CA40 and CA60 elevated (P < 0.05) relative expression of cell junction proteins (Claudin-1/-2 and ZO-1/-2/-3) and MUC-2 in duodenum, while decreased (P < 0.05) relative expression of TLR2, TLR4, and the concentrations of IL-6, IL-10, TNF-α, TGF-β1 in duodenum. CA40 also increased (P < 0.05) the α-diversity of the cecal microbiota and boosted (P < 0.05) the relative abundance of beneficial phyla and genera, particularly Firmicutes, Anaerofilum, and Papilibacter. In conclusion, dietary supplementation with carnosic acid showed protective effects on the growth performance and intestinal health in challenged broilers by down-regulating the expression of TLRs (TLR2/4) and inhibiting the production of inflammatory cytokines, strengthening the tight junction in intestinal epithelial cells, and enhancing the diversity of microbiota and the relative abundance of beneficial bacteria. When supplemented to diet of broilers, 40 mg/kg carnosic acid was recommended.