Effects of fermented cottonseed meal on growth performance, apparent digestibility and intestinal health of yellow catfish (Pelteobagrus fulvidraco)

To investigated the effects of fermented cottonseed meal on the apparent digestibility of diets and intestinal health in yellow catfish (Pelteobagrus fulvidraco), three dietary groups were designed. The first group consisted of a basic diet, with fish meal and soybean meal as the primary protein sources. The second and third groups were composed of 70% basic diet supplemented with 30% unfermented or fermented cottonseed meal, respectively. The weight gain rate (WGR) and specific growth rate (SGR) of P. fulvidraco fed the fermented cottonseed meal diet were significantly higher than those of fish fed the unfermented cottonseed meal diet. Solid-state fermentation of cottonseed meal significantly enhanced its digestibility in P. fulvidraco, with dry matter digestibility increasing from 35.64% to 82.10%, crude protein digestibility from 77.31% to 90.04%, crude fat digestibility from 68.53% to 88.03%, and energy digestibility from 48.43% to 86.24%. Compared with unfermented cottonseed meal, the fermented meal significantly increased intestinal villus height and width, decreased mRNA expression of pro-inflammatory factors (il6 and il8), and increased mRNA expression of anti-inflammatory factor tgf-β. Additionally, the fermented meal significantly increased mRNA expression of antioxidant-related genes (cat, sod1, sod2, gpx1, and keap1), while decreasing nrf2 mRNA expression. Total antioxidant capacity (T-AOC), catalase (CAT), and total superoxide dismutase (T-SOD) activities were significantly elevated, and malondialdehyde (MDA) content was reduced. The mRNA expression levels of tight junction-related genes (zo1, zo2, claudin1, claudin3, claudin4, and occludin) were also significantly increased. Furthermore, mRNA expression of apoptosis-related genes (caspase3, caspase9, and p53) was significantly decreased, while the mRNA expression of the anti-apoptosis protein bcl2 was significantly elevated, and enzyme activities of Caspase3 and Caspase9 were significantly reduced. In conclusion, solid-state fermentation of cottonseed meal can significantly improve growth performance and nutrient digestibility in P. fulvidraco and mitigate the adverse effects of cottonseed meal on intestinal health.