Effects of yeast on inflammatory responses in yellow-feathered broilers induced by single and multiple lipopolysaccharide stimulation

Abstract

This study investigated the effect of yeast on the growth performance and inflammation of yellow-feathered broilers challenged with lipopolysaccharide (LPS). Four hundred and eighty-one-day-old broilers (BW 38.5±1.01 g) were randomly divided into six treatments with eight replicates of 10 birds each and fed a basal diet with or without 0.025% antibiotics and 0.05 and 0.5% yeast (Saccharomyces cerevisiae, 1.0 × 1010 cfu/g), respectively. Broilers from each replication were intra-abdominally injected with LPS (1.0 mg/kg body weight) or saline at 21, 23, 25, and 27 d of age. Samples were obtained after 3 or 12 h of the first injection (d 21) and the last injection (d 27), respectively. The results showed that LPS stimulation resulted in a significant decrease in productive performance (P<0.01) and a significant decrease in splenic index (P<0.05). Lipopolysaccharide injection caused significant (P<0.01) increase in serum α-AGP in the first hour and haptoglobin in the last 3 h (P<0.01), while other acute phase proteins were not significantly affected. All chickens fed diets supplemented with 0.5% yeast had elevated serum levels of IgA (P = 0.094) and lysozyme (P = 0.067) at 12 h of the first injection compared with those fed antibiotic diets. Lipopolysaccharide injection substantially increased the levels of cytokines in serum. A trend toward decreased levels of IL-10 (P = 0.078), transforming growth factor-beta 1 (P = 0.075), and interferongamma (P = 0.061) was observed in the LPS-stimulation × diet interaction. There was an LPS-stimulated × diet interaction (P<0.05) for interleukin-1beta transcript levels in the liver 12 h after repeated LPS injections. Chickens fed diets with 0.05 or 0.5% yeast tended to have higher levels of toll-like receptor 4 (P = 0.074) transcripts in the spleen at 3 h and β-defensin 1 (P = 0.065) transcripts at 12 h compared with those fed diets with antibiotics. The addition of 0.05 or 0.5% yeast alleviated the adverse effects caused by LPS injection, and this study provided a reference for the application of yeast in the broiler industry.