Evaluation of a synergistic blend of short- and medium-chain fatty acids as a dietary intervention for the effective management of Vibriosis in shrimp culture

Vibriosis caused by Vibrio spp. is imposing severe havoc and adverse effects on shrimp culture. Antibiotics are the most widely used therapeutic measures against vibriosis. However, the uncontrolled use of antibiotics may spread the antibiotic residues and increase antibiotic-resistant bacteria. In this study, a product based on a synergistic blend of short- and medium-chain fatty acids (Selacid® GG, herein referred as Sel) was evaluated against vibriosis in shrimp, P. vannamei. The shrimps (n=30 in triplicate per treatment) were fed with Sel (0.0%, 0.1%, 0.2% or 0.3%) for 14 days. The shrimp were challenged on 8^th day by immersion, and the samples were collected on the 6^th day post-challenge and the 14^th day post-feeding. The shrimp fed with Sel (0.1%, 0.2%, and 0.3%) diet showed significantly higher total haemocyte count, while the phenoloxidase activity was significantly increased in the Sel 0.2% diet fed group. Histological analysis unveiled inflammatory responses with haemocytic infiltration, encapsulation, and granuloma in Sel 0.2% diet-fed shrimps with less degeneration and necrosis of hepatopancreas tubules and epithelial cells. qPCR analysis of vibrio loads in hepatopancreas revealed significantly lower vibrio count in all Sel diet-fed groups and further confirmed by culture-dependent method which showed significantly lower total vibrio count in the hepatopancreas and haemolymph of Sel 0.2% and Sel 0.3% diet fed shrimp. Growth parameters showed significantly higher values in weight gain, specific growth rate, and survival rate in Sel 0.2% diet-fed shrimps. Thus, the current study confirms the efficacy of Sel (0.2%) against vibriosis by enhancing the immune and inflammatory responses, reducing vibrio load and improving the growth and survival. Hence Sel, can be used as an alternative therapeutic for managing vibriosis in shrimp aquaculture.