The present study aimed to assess the effects of three probiotic-supplemented diets on growth, cecal fermentation, blood biochemical, and intestinal morphological features in growing rabbits reared under summer conditions. Rabbits were allotted into four groups: G1 rabbits were fed the basal diet (control), G2 rabbits received Enterococcus faecium (EF) and Clostridium butyricum (CB) complexes (1 × 108 and 2.5 × 106 cfu/kg diet, respectively), G3 rabbits were given CB (2.5 × 106 cfu/kg diet) and yeast complexes (1 g/kg diet), and G4 rabbits received EF (2 × 108 cfu/kg diet) and yeast (1 g/kg diet). G2 rabbits exhibited the highest performances in terms of enhanced body weight and weight gain, protein efficiency ratio and feed conversion ratio (P<0.05). Serum total protein, globulin, immunoglobulin M, and highdensity lipoprotein concentrations were higher in probiotic-fed rabbits than those in controls. Additionally, lipid profile parameters were significantly reduced in the probiotic-fed rabbits, with the lowest concentrations measured in G4 rabbits (P<0.05). Rabbits given EF and CB had the highest total volatile fatty acid (VFA ) and propionic acid levels and the lowest ammonia concentrations. Increased villi length and muscular layer thickness and reduced crypt depth were observed in rabbits receiving EF and CB compared with the values obtained in controls (P<0.05). In summary, supplementing fattening rabbit diets with EF and CB, as a novel formulation, might be a promising and easy method to enhance growth performance under hot climate conditions by improving the feed utilization, immune response, serum lipid profile, cecal VFA production, and duodenal morphology.
