Leukocyte phagocytosis and lysozyme activity in Nile tilapia fed supplemented diet with natural extracts of propolis and Aloe barbadensis.

Although there is evidence on the benefits in the use of immunostimulants in aquaculture, there are few commercial products being used. This study evaluated the use of natural substances as potential sources for the production of immunostimulants. Propolis and Aloe barbadensis have been widely studied and its extracts have different chemical constituents responsible for antimicrobial, anti-inflammatory and immunostimulant. Tilapia juveniles were fed for two weeks with diets supplemented mix of propolis extracts and aloe (1:1) in different concentrations: 0.5, 1 e 2%. After the experimental period, fish blood was collected for hematoimmunological as follows : hematocrit, total plasma protein, erythrocytes (RBC), leukocytes (WBC), differential leukocyte count, phagocytic activity, serum lysozyme activity, and serum antimicrobial activity, serum antimicrobial activity (evaluated against Aeromonas hydrophila, Enterococcus durans and Escherichia coli). Except for higher number of thrombocytes in 1%-supplemented fish, the rest did not show significant difference.

Immunomodulatory effects of decaffeinated green tea (Camellia sinensis) on the immune system of rainbow trout (Oncorhynchus mykiss).

In order to study the immunomodulatory effects of decaffeinated green tea extract on rainbow trout, a study with a 30-day feeding trial was conducted. Commercial diets with graded levels of decaffeinated green tea extract, 20 mg (T1), 100 mg (T2), 500 mg (T3) per kg feed were prepared. 120 rainbow trout (35 ± 3 g) were randomly assigned to 4 groups in triplicates and fed one of the 3 experimental diets formulated or control diet. After feeding trial, 12 fish from each group were sampled for analysis of some immunological parameters. Remaining fish were injected with 0.5 ml of chicken red blood cell (C-RBC) suspension (2%) intraperitoneally on days 5 and 15 after feeding trial. Results of the current study showed that the inclusion of 20 mg kg-1 green tea (T1) in fish diet enhanced the serum bactericidal activity against Yersinia ruckeri, while significant elevation of lysozyme activity was shown in T2 group. Anti-trypsin activity due to α1-antiprotease was significantly higher in T1 and T2 groups while peroxidase content showed significant increase in all treatment groups compared to control group. Hemagglutination antibody titer against C-RBC was significantly higher in fish administered with 100 mg kg(-1) green tea (T2). Our findings showed that decaffeinated green tea in lower doses of administration could be optimum to enhance the immunity of rainbow trout.