Dietary xylooligosaccharides modulate oxidative stress and pathogen resistance in growing rabbits.

BACKGROUND: Given the high incidence of gastrointestinal disorders in intensive rabbit production, we assessed the effects of graded levels of xylooligosaccharides (XOS) on growth performance, nutrient digestibility and intestinal health in growing rabbits. METHODS: The 35-day-old weaned rabbits (889.41 ± 0.41 g) were randomly assigned to five dietary treatments (0, 0.2, 0.3, 0.4 or 0.5 g/kg XOS) and the trial lasted for 35 d. RESULTS: The results revealed that linear trend responses of body weight (BW) to XOS on d 21 and 35 (P ≤ 0.05). During d 1-21, 0.2 g/kg XOS increased average daily feed intake (ADFI) while 0.5 g/kg improved feed conversion ratio (FCR) significantly (P ≤ 0.05). Weight gain rate (WGR) showed a linear trend, while FCR showed a quadratic response (P ≤ 0.05). Throughout the 35-d trial, 0.2 and 0.3 g/kg XOS enhanced ADFI, and 0.4 g/kg XOS improved FCR significantly, average daily gain (ADG) demonstrated linear dose-responsiveness, while WGR and FCR showed quadratic trends (P ≤ 0.05). Notably, 0.2 g/kg XOS elevated serum glutathione peroxidase (GSH-Px) activity and ileal secretory immunoglobulin A (sIgA) levels. Furthermore, 0.3, 0.4 and 0.5 g/kg XOS reduced jejunal malonaldehyde (MDA) content, 0.4 g/kg XOS decreased serum MDA, and 0.5 g/kg XOS elevated serum immunoglobulin M (IgM) significantly (P ≤ 0.05). 0.2, 0.4, 0.5 g/kg XOS improved the digestibility of crude fiber (CF), 0.2 and 0.4 g/kg XOS increased acid detergent fiber (ADF), and neutral detergent fiber (NDF) also increased among all treatments, although 0.5 g/kg XOS reduced cellulase activity significantly (P ≤ 0.05). Furthermore, graded levels of XOS significantly changed the relative abundance of specific bacteria, and 0.4 and 0.5 g/kg XOS enhanced the content of valeric acid significantly (P ≤ 0.05). CONCLUSIONS: In conclusion, dietary supplementation of XOS serves as an effective nutritional strategy to optimize bacterial community in the cecum, improve fiber digestion and valeric acid production, while enhances resistance to intestinal pathogen infection and oxidative stress in rabbit production.