Evaluation of dietary oyster mushroom on intestinal histology, growth performance, and immuno-serological parameters of juvenile rainbow trout

In this study, the effects of nutritional supplementation with oyster mushroom extract on the nonspecific immune response, gut histology, and growth performance of rainbow trout were investigated. Sixty fish (weighing 20 g) were placed in tank groups, and groups were established. The control fish were fed with commercial pellets, and the other two experimental group fish were fed with experimental diets containing oyster mushroom extracts for six weeks. During the trial, biometrical, immunological, and biochemical parameters were assessed in one, two, three, four, five, and six weeks. Also, gut samples were taken at the same sampling weeks. The intracellular respiratory burst, bactericidal activity, total protein, and globulin were significantly enhanced in fish fed 2% experimental diet in three, four, five, and six weeks. Compared to the control group, the fish group which received 2% supplemented diet showed elevated cholesterol levels in serum at the first week followed by decrease in the third and sixth weeks. Some biochemical parameters (glucose, albumin, and triglycerides) were not affected. Moreover, the feeding with dietary extract did not show any negative impact on the histology of the gut and growth performance of fish. These results indicated oyster mushroom extract may effectively enhance non-specific immune parameters in juvenile rainbow trout.