Control of motile Aeromonas septicemia in Nile tilapia, Oreochromis niloticus using some herbal additives

Abstract

This work aimed to investigate the effect of dietary thyme (Thymus vulgaris) and rosemary (Rosmarinus officinalis) on controlling Aeromonas hydrophila (A. hydrophila) infection in Nile tilapia (Oreochromis niloticus). Fish were divided into three groups in duplicate and were fed on experimental diets (0% control, 1.5% thyme, and 0.5% rosemary) for 6 weeks before the challenge trial with A. hydrophila. Three sampling points were carried out after 2-, 4-, and 6-weeks post-feeding. Results revealed that serum lysozyme activity significantly increased after 2 weeks in both treated groups compared to controls. Serum nitric oxide recorded a significant decrease in thyme supplemented group during the experiment. Nile tilapia-fed thyme or rosemary exhibited a significant (P< 0.05) increase in total leukocyte count, neutrophils, and monocytes throughout the experimental period. Meanwhile, lymphocytes recorded a significant increase in both treated groups after 4 and 6 weeks of feeding compared to the control. In addition, thyme treated group showed a significant increase in superoxide dismutase (SOD) and glutathione reductase (GR) enzymes activities after 4 weeks of feeding. Malondialdehyde (MDA) decreased significantly at 6 weeks of feeding compared to the control. The challenged fish fed 1.5 % thyme and 0.5 % rosemary for 4 and 6 weeks showed high survivability, 90 %, compared to only 10 % of the control. In conclusion, dietary supplementation with thyme and rosemary in Nile tilapia could increase fish's resistance to A. hydrophila by improving immune-hematological parameters. Aeromonas hydrophila ImmunityNile tilapia Rosemary Thyme.