Effects of fermented soybean meal with Bacillus velezensis, Lactobacillus spp. or their combination on broiler performance, gut antioxidant activity and microflora

Abstract

Objective: A series of experiment were conducted to evaluate the effects of replacing a part of soybean meal (SBM) at 6% of broiler diets with fermented soybean meal (FSBM) obtained by single or two-stage fermentation by measuring growth performance, antioxidant activity in the jejunum and distal intestinal microflora.Methods: Soybean meal samples were prepared by single-stage fermentation using <i>Bacillus velezensis</i> (Bv) (FSBM_B), or <i>Lactobacillus</i> spp. (as commercial control) (FSBM_L). Additional SBM sample was prepared by two-stage fermentation using Bv and subsequently using <i>Lactobacillus brevis</i> ATCC 367 (Lb) (FSBM_B+L). Enzyme activity, chemical composition, trichloroethanoic acid-nitrogen solubility index (TCA-NSI) and antioxidant activity were measured. Then, in an <i>in vivo</i> study, 320 Ross308 broilers were divided into four groups with <i>ad libitum</i> supply of feed and water. Four groups were fed either a corn-soybean meal diet (SBM), or one of fermented SBM diets (FSBM_B+L, FSBM_B, and FSBM_L). Growth, serum characteristics, microflora, and the mRNA expression of selected genes were measured.Results: Compared to SBM, FSBM_B+L contained lower galacto-oligosaccharide, allergic protein, and trypsin inhibitor, and higher TCA-NSI by about three times (p<0.05). Reducing power and 1,1-diphenyl-2-picrylhydrazyl free radical scavenging ability correlated positively with the TCA-NSI content in FSBM. Growth performances were not significantly different among four groups. In jejunum of 35-day-old broilers, partial replacement of SBM by FSBM_B+L increased the activity of superoxide dismutase and catalase (<i>CAT</i>), and the FSBM_B group had the highest catalase activity (p<0.05). Partial replacement of SBM by FSBM increased relative mRNA expressions of nuclear factor erythroid 2-related factor 2 (<i>Nrf2</i>), heme oxygenase-1 (<i>HO-1</i>), and peptide transporter 1 (<i>PepT1</i>) (p<0.05); however, FSBM_B+L increased <i>CAT</i> mRNA level to 5 times of the control (p<0.05).Conclusion: Using Bv- and Lb-processed SBM through two-stage fermentation to partially replace 6% of diets will improve the gut's antioxidant activity under commercial breeding in broilers.