Dietary supplementation with synbiotics improves growth performance, antioxidant status, immune function, and intestinal barrier function in broilers subjected to cyclic heat stress.

Abstract

This study investigated the effects of synbiotics supplementation on growth performance, antioxidant status, immune function, and intestinal barrier function in broilers subjected to cyclic heat stress. One hundred and forty-four 22-day-old male broilers were randomly assigned to one of three treatment groups of six replicates each for a 21-day study, with eight birds per replicate. Broilers in the control group were reared at a thermoneutral temperature and received a basal diet. Broilers in the other two heat-stressed groups were fed a basal diet supplemented without (heat-stressed group) and with 1.5g/kg synbiotic (synbiotic group). One and a half gram of the synbiotic consisted with 3 × 109 colony forming units (CFU) Clostridium butyricum, 1.5 × 109CFU Bacillus licheniformis, 4.5 × 1010CFU Bacillus subtilis, 600mg yeast cell wall, and 150mg xylooligosaccharide. Compared with the control group, heat stress increased rectal temperatures at 28, 35, and 42days of age, respectively (P < 0.05). Birds subjected to heat stress had reduced weight gain, feed intake, and feed efficiency during 22 to 42days (P < 0.05). In contrast, supplementation with the synbiotic decreased rectal temperature at 42days of age and elevated weight gain of heat stress-challenged broilers (P < 0.05). Heat-stressed broilers exhibited a lower superoxide dismutase (SOD) activity in jejunal mucosa and a higher malondialdehyde accumulation in serum, liver and jejunal mucosa (P < 0.05), and the regressive SOD activity was normalized to control level when supplementing synbiotic (P < 0.05). Heat stress increased interleukin-1β (IL-1β) and interferon-γ (IFN-γ) levels in serum and IL-1β content in jejunal mucosa of broilers (P < 0.05). Synbiotic reduced IL-1β level in serum of broilers subjected to heat stress (P < 0.05). Compared with the control group, elevated serum diamine oxidase activity and reduced jejunal villus height were observed in broilers of the heat-stressed group (P < 0.05), and the values of these two parameters in the synbiotic group were intermediate (P > 0.05). Heat stress upregulated mRNA abundance of IL-1β and IFN-γ and downregulated gene expression levels of occluding and zonula occluden-1 (ZO-1) in jejunal mucosa of broilers (P < 0.05). The alterations in the mRNA expression levels of jejunal IL-1β and ZO-1 were reversed by the synbiotic (P > 0.05). In conclusion, dietary synbiotics could improve growth performance, antioxidant capacity, immune function, and intestinal barrier function in heat-stressed broilers.