Effects of dietary yeast culture supplementation on growth performance, nonspecific immunity and intestinal health of Pelteobagrus fulvidraco

An 8-week feeding trial was conducted to evaluate the effects of dietary yeast culture supplementation on growth performance, nonspecific immunity and intestinal health of Pelteobagrus fulvidraco. Yeast culture YC1 (50% crude protein), yeast culture YC2 (55% crude protein) with 0, 1% and 2%, respectively were added to basic diet, and five practical diets with iso-nitrogenous and iso-lipidic (42% crude protein and 8% crude lipid) were prepared, named C, YC1-1, YC1-2, YC2-1 and YC2-2, respectively. A total of 375 P. fulvidraco with an average initial body weight about (4.87±0.00) g were randomly allocated into five groups with three replicates per group and 25 fish per replicate. The results indicated that fish fed the diets containing YC2-1 and YC2-2 had higher weight gain rate (WGR) than that fed the control diet of P. fulvidraco, and the highest specific growth rate (SGR) was observed at YC2-2 treatment among all treatments. Fish fed the diets containing YC2-1 and YC2-2 had higher productive protein value (PPV) than that fed the control diet of P. fulvidraco. Protein efficiency rate (PER) increased at first and then decreased with the increase of yeast culture addition level, and YC2-1 treatment had the highest PER among all treatments. Fish fed the diets containing YC2-1 and YC2-2 had lower feed coefficient rate (FCR) than that fed the control diet of P. fulvidraco, and YC2-2 treatment had lower FCR than that the YC2-1 treatment. Fish fed the diets containing YC2-1 and YC2-2 had higher activity of lysozyme (LSZ) and superoxide dismutase (SOD) than that fed the control diet in the liver of P. fulvidraco. Fish fed the diets containing YC2-1 had higher height of intestinal folds than that fed the YC1-1 diet of P. fulvidraco, and fish fed the diets containing YC2-1 had greater width of folds and height of epithelial cells than that the YC2-2 treatment of P. fulvidraco. In the experiment of Aeromonas hydrophila challenge, fish fed the diets containing yeast culture had lower average cumulative mortality rates (CMR) than that fed the control diet of P. fulvidraco, and the lowest CMR was observed at YC2-1 treatment among all treatments. In conclusion, under the experimental conditions, adding yeast culture YC2 to diet can effectively improve the nonspecific immune function of P. fulvidraco, improve its antioxidant capacity, maintain intestinal health and improve its ability to resist A. hydrophila infection.