Effects of dietary probiotic supplements on growth, digestive enzymes activity, intestinal histomorphology and innate immunity of common carp (Cyprinus carpio): a field study

In this study, the effects of two probiotic strains (Lactobacillus plantarum and Lactobacillus rhamnosus) and a commercial product containing probiotic (Synbiozyme 500®) were investigated on innate immunity, growth performance, digestive enzymes activity and intestinal histomorphology of common carp. A total of six thousand common carp (60 ± 10.44 g) were randomly allocated into five earthen ponds. The fish in each pond were fed with the following experimental diets for 6 months: basal diet containing L. plantarum (D1), L. rhamnosus (D2), commercial probiotic (Synbiozyme 500®, D3), L. plantarum + L. rhamnosus (D4) and without any probiotic (D5). Growth parameters were measured at the beginning (day 0) and the end (day 180) of study. Tissue and blood samples were taken at days 0, 90 and 180. According to the results, growth performance was not affected by the probiotic supplements (p > 0.05). The activities of intestinal lipase, trypsin, chymotrypsin, protease, α-amylase and alkaline phosphatase (ALP) were significantly (p < 0.05) enhanced in fish fed with Synbiozyme 500® and L. plantarum + L. rhamnosus for 90 days. Likewise, intestinal villi height in the D3 group, and intestinal villi width, thickness of gut epithelium and the number of intestinal goblet cells in the D3 and D4 groups were significantly (p < 0.05) higher relative to the control group after 90 days. The levels of total immunoglobulin were significantly (p < 0.05) increased in the D4 group than the other groups at day 90. Serum bactericidal and antiprotease activities were significantly (p < 0.05) higher in all probiotic groups than the control group at the end of study (day 180). The results indicated that fish-derived probiotics (L. plantarum + L. rhamnosus) and Synbiozyme 500® have high potentials for positive modulation of digestive enzymes activity, immune responses and intestinal histomorphology of common carp reared in pond.