Effects of oligosaccharides in a soybean meal-based diet on fermentative and immune responses in broiler chicks challenged with Eimeria acervulina.

Fermentable oligosaccharides, particularly those found in soybean meal (SBM), may modulate fermentation in the ceca, thus affecting intestinal immune responses to intestinal pathogens. We hypothesized that fermentable oligosaccharides found in SBM would positively affect cecal fermentation and intestinal immune status in chicks challenged with an acute coccidiosis (Eimeria acervulina) infection and fed either a SBM-based diet or a semi-purified soy protein isolate- (SPI) based diet. Using a completely randomized design, 1-d-old broiler chicks (n = 200; 5 replications/treatment; 5 chicks/replication) were assigned to 1 of 4 SBM- or SPI-based diets containing either dietary cellulose (4%) or a fermentable carbohydrate, galactoglucomannan oligosaccharide-arabinoxylan (GGMO-AX) complex (4%). On d 9 posthatch, an equal number of chicks on each diet were inoculated with either distilled water (sham control) or E. acervulina (1 × 10(6) oocysts) and then euthanized on d 7 postinoculation. Overall, body weight gain and feed intake were greater (P < 0.01) for SBM-fed chicks, regardless of infection status. Gain:feed ratio was greater (P ≤ 0.05) for SPI-fed chicks except during d 3-7 postinoculation. Infection status, but not fiber source, affected propionate, isobutyrate, isovalerate, and total branched-chain fatty acid concentrations (P ≤ 0.02). Soybean meal-based diets resulted in greater (P ≤ 0.04) short-chain fatty acid and branched-chain fatty acid concentrations than SPI-based diets. Messenger RNA fold changes relative to uninfected SBM-cellulose-fed chicks of all duodenal cytokines were greater (P ≤ 0.01) for infected chicks, and SBM-fed chicks had greater (P < 0.01) interferon-γ and interleukin-12β expression compared with SPI-fed chicks. Cecal tonsil cytokine expression was also affected (P ≤ 0.02) by infection; however, protein source only affected (P < 0.01) interleukin-1β expression in this tissue. Overall, a SBM-based diet, compared with a semi-purified SPI-based diet with a different ingredient composition, resulted in greater weight gain, feed intake, and short-chain fatty acid production regardless of infection status, and also greater duodenal cytokine expression in E. acervulina- infected chicks, which is hypothesized to be related to the nutrients and oligosaccharides found in SBM.