Abstract
•Varied levels of yeast fermented date palm seed meal (DSM) were included in Nile tilapia diets (0, 5, 10, 15 and 20 %).•Fermented DSM significantly affected the growth performance and feed utilization in a dose dependent manner.•Dietary fermented DSM significantly increased the activities of digestive enzymes and intestinal morphometry.•The blood haemato-immunological variables were altered by the inclusion of fermented DSM.•The inclusion of fermented DSM at 11.44–17.44 % can be used efficiently in tilapia’ diets.
Varied levels of Saccharomyces cerevisiae-fermented date palm seed meal (DSM) were included in Nile tilapia (26.95 ± 0.01 g) diets. Five diets were prepared to include fermented DSM at 0, 5, 10, 15 and 20 % and fed for fish for 8 weeks. The obtained results revealed that yeast fermented DSM significantly affected the final body weight, weight gain, specific growth rate, and feed conversion ratio in a dose dependent manner (P = 0.001, P = 0.002, P = 0.004, P = 0.01, respectively). Dietary yeast fermented DSM significantly increased the lipase, amylase, and protease activities (P = 0.011, P = 0.02, P = 0.031, respectively). In the anterior segment of the intestine, villus length and the number of goblet cells were significantly affected by the inclusion of yeast fermented DSM (P = 0.001 and P = 0.008). In the middle area, only the villus length, internal villi distance, and goblet cells number were affected significantly by the inclusion of yeast fermented DSM (P = 0.001, P = 0.02, P = 0.047, respectively). Posterior intestinal morphometry showed significantly increased villus length and number of goblet cells when fish fed yeast fermented DSM in a dose dependent manner (P = 0.028 and P = 0.04). Most of the measured blood parameters showed insignificant (P > 0.05) differences except for total blood protein, globulin, albumin, RBCs, and WBCs which were significantly affected by the inclusion of yeast fermented DSM (P = 0.001, P = 0.001, P = 0.007, P = 0.042, P = 0.001, respectively). Furthermore, dietary yeast fermented DSM significantly altered the lysozyme and phagocytic activities (P = 0.03 and P = 0.005). Based on the polynomial regression analysis the inclusion of yeast fermented DSM at 11.44–17.44 % can be used effectively in tilapia’ diets for improving the growth, digestion activity, and immune response.