This study investigated the possible effects of using Pediococcus pentosaceus in common carp (Cyprinus carpio) diet on the growth performance, digestive enzyme activities, haematological indices, and innate immune responses. Four diets were prepared, including a control diet and three diets supplemented with P. pentosaceus at 107, 108, and 109 CFU g−1. After 45 days, fish fed P. pentosaceus at 108 CFU g−1 had significantly higher final body weight, weight gain, and specific growth rate when compared to the control group (P < 0.05). Furthermore, fish fed P. pentosaceus at 108 CFU g−1 had mainly enhanced the digestive enzyme activities, respect to the control fish (P < 0.05). However, the total viable heterotrophic aerobic bacteria were significantly elevated after feeding low dose of P. pentosaceus (P < 0.05). Among haematological parameters, red blood cells (RBCs), white blood cells (WBCs), hemoglobin (Hb), and hematocrit (HCT) were significantly (P < 0.05) increased in fish fed 108, and 109 CFU g−1 of P. pentosaceus. Serum total antibody level, alternative complement, protease, and lysozyme activities, as well as antibacterial activity, were significantly enhanced in fish fed with different doses of P. pentosaceus in comparison with the control group (P < 0.05). The obtained results revealed that P. pentosaceus could be used as a beneficial probiotic to improve the growth performance, digestive enzymes activity, and haemato-immunological responses in common carp culture.
