Effects of kefir on growth performance, serum biochemistry, immune responses, histopathology and Aeromonas hydrophila infection in common carp (Cyprinus carpio L. 1758)

The aim of this study was to investigate the antimicrobial effects of kefir as a dietary supplement on the growth and infection caused by Aeromonas hydrophila in Cyprinus carpio. Totally, 72 juvenile carp weighing approximately 10-15 g were used. The fish were divided into 4 groups fed with 3, 5 and 10% kefir and the control group (without adding kefir) with three replications (six fish per replication) and were fed 3% of their body weight daily. The antimicrobial effect of kefir against A. hydrophila was investigated as well. After two weeks, the levels of IgM, ALT, AST, ALP and total protein in fish serum were evaluated. The liver, kidney and spleen tissues of fish were examined for histological study. The results showed that the 48-h kefir product had the highest antimicrobial effect against A. hydrophila. Feeding the fish with 3% kefir caused significant increases in length and weight of the fish. The statistical analyses revealed that the levels of IgM, AST, ALP and the serum total protein were not significantly different between the four groups, while the average amount of ALT in treatment 3% exhibited significant difference, which was less than the other two groups, while was not significantly different from the control. All experimental groups exposed to A. hydrophila revealed tissue damage in liver, kidney and spleen. However, tissue damage was less in treatment 3%.