Garlic dietary supplementation positively modulates the immune system and intestinal morphology of juveniles of the Cobia Rachycentron canadum
Cobia presents great potential for production due to its high growth rate, rusticity during handling and high market value, being the only species of marine fish that has been commercially produced in Brazil. The application of substances with immunostimulating properties, such as garlic, has been considered an efficient approach to health management in fish in aquaculture. Therefore, the objective of the present study was to determine the effects of the addition of garlic to the diet on zootechnical performance and on hematological and immunological indexes of juveniles of Cobia Rachycentron canadum. Juveniles with ~ 170 g and 30 cm were stored in six 12 m3 10 net tanks (40 juveniles per net tank) at Maricultura Costa Verde, south coast of Rio de Janeiro.Three tanks were fed with wet food (control) and three tanks with wet food with 1% of the total wet weight added garlic/kg (treatment). The fish were fed twice a day for 68 days. At the end of the experimental period, no significant differences (P> 0.05) were observed in the zootechnical performance between treatments. The zootechnical indexes between the control and the treatment were, respectively: weight gain was 80 and 93%; final biomass was 12.62 kg and 12.66 kg; apparent feed conversion rate 4.9 and 5.5 and 99 and 97% survival. Circulating lymphocytes were significantly higher, as well as a greater phenotypic expression in CD3 (cel/mm2) and CD4 (cel/mm220) lymphocytes was observed in the kidneys of fish fed garlic-containing diets. Monocytes (%), thrombocytes (%) and N ratio:L were significantly higher in fish that were fed without garlic. In the middle portion of the intestine the villus height (mm) and vacuole numbers (mm) were also higher in fish fed with the addition of garlic. Therefore, garlic benefited the immune system and intestinal morphology of juveniles from Cobia, and its inclusion in the fish diet is recommended.