The present study was carried out to investigate the effect of both nutmeg powder and its aqueous extract on the immune response of Nile tilapia (Oreochromis niloticus) and resistance against Aeromonas veronie infection. Antibacterial activity of nutmeg aqueous extract was studied against some strains of Gram negative and positive bacteria. Fish (average body weight 40±5.0 g) were randomly distributed into seven groups. Fish fed diet containing 1200 mg/kg Myristica fragrans (MF) aqueous extract and 3 % powder showed significant decrease in lysozyme activity after 1stweek feeding compared to the control fed basal diet. While after two weeks feeding, there were no significance differences in lysozyme activity (p ≥ 0.05) among groups fed MF aqueous extract at a concentration of 400, 800, and 1200 mg/kg diet and fish fed 1, 2, and 3% MF powder. Respiratory burst activity after 1st and 2nd weeks feeding showed significant decrease in all groups either fed MF powder or its aqueous extract, except group fed 3 % MF powder showed no significant difference compared to the control. After two weeks feeding, all seven treated group were divided into subgroups I (continued fed the same feeding regime) and subgroup II (switched to basal diet) for additional 6 weeks. Almost subgroups II returned to basal diet exhibited enhancement in lysozyme activity and respiratory burst activity after 4th and 8th weeks feeding compared to the control. MF aqueous extract recorded no antimicrobial activity against Gram negative (Aeromonas hydrophila, Aeromonas veronii, Aeromonas sobria, Aeromonas jandaei, and Pseudomonas fluorescences) and positive (Staphyloccoccus aureus and streptococcus sp) bacteria. The experimentally infected fish with Aeromonas veronie in subgroup-I and II of 400 MF aqueous extract revealed low mortality rate 60 % compared to 80 % mortality in the control group. Moreover, subgroup I and II of fish fed 3 % MF powder recorded 100 % mortality. These results concluded that dietary supplementation of whole seed nutmeg powder or its aqueous extract negatively affects the immune response and disease resistance of Nile tilapia. |
