Effects of fermented feed on growth performance, immune organ indices, serum biochemical parameters, cecal odorous compound production, and the microbiota community in broilers

The aim of this study was to explore the effects of dietary fermented feed addition on growth performance, immune organ indices, serum biochemical parameters, cecal odorous compound production, and the bacterial community in broilers. A total of 480 broiler chicks (1-day-old) were randomly assigned to 6 groups, including a basal diet (control group), a basal diet supplemented with 10, 15, 20, and 25% dried fermented feed, and 10% wet fermented feed. Each group contained 8 replicates of 10 chicks each. The results showed that fermentation increased (P < 0.05) the total acid level and the number of Lactobacillus, Yeast, and Bacillus. The 15% dried fermented feed group had an increased (P < 0.05) body weight (BW) than the control, while the 25% dried fermented feed group had the lowest (P < 0.05) BW on 42 d. Compared to the control group, the feed intake (FI) was increased (P < 0.05) in the 10, 15% dried and 10% wet fermented feed groups from 22 to 42 d and from 1 to 42 d. No significant difference (P > 0.05) was observed in feed conversion ratio (FCR) among all groups. Supplementation with fermented feed increased (P < 0.05) the bursa of Fabricius index but not (P > 0.05) the thymus and spleen indices. Compared with the control, the broilers fed fermented feed had increased (P < 0.05) serum total protein, albumin, globulin, IgA, IgG, IgM, lysozyme, complement 3, and complement 4 levels. The cecal concentrations of acetic acid, propionic acid, butyric acid, and lactic acid were increased and the pH values were decreased in the fermented feed groups (P < 0.05). Among the groups, the 15% dried fermented feed group showed the lowest concentrations of skatole and indole in the cecum (P < 0.05). The composition of the cecal microbiota was characterized, in which an increased abundance of Ruminococcaceae, Lactobacillaceae, and unclassified Clostridiales and a decreased abundance of Rikenellaceae, Lachnospiraceae, and Bacteroidaceae were found in the fermented feed groups. Taken together, dietary fermented feed supplementation can improve growth performance, immune organ development, and capacity and decrease cecal odorous compound production, which may be related to the regulation of microbial composition.