Effects of Piper betle and Phyllanthus emblica leaf extracts on the growth and resistance of black tiger shrimp, Penaeus monodon , against pathogenic Vibrio parahaemolyticus

The effect of betel ( Piper betle ) and amla ( Phyllanthus emblica ) leaf extracts as feed supplement was studied on the growth and immune functions of the shrimp Penaeus monodon when exposed to a virulent strain of Vibrio parahaemolyticus . Six experimental groups (PB-1, PB-2, PB-3 and PE-1, PE-2, PE-3) of shrimp were fed extract at varying concentrations, 0.05%, 0.1%, and 0.2%, before being compared to a control group that did not receive any extract. After a feeding trial of 4 weeks, each group of shrimp was challenged with V. parahaemolyticus at a concentration of 10 6 CFU/mL and monitored for 2 weeks. The lowest concentration of P. betle extract and the moderate concentration of P. emblica extract in the diet induced a significant increase in shrimp growth performance parameters (final body weight, weight gain, specific growth rate) and feed utilization efficiency (low feed conversion ratio, high protein efficiency ratio). The dietary extracts also exhibited a significant positive influence on the immunological parameters such as total haemocyte count, prophenoloxidase activity, and superoxide dismutase activity before and after the challenge with V. parahaemolyticus . Compared to the control group, the total Vibrio load was significantly lower in the shrimp groups fed with extracts with the highest Vibrio density found in the hepatopancreas. The cumulative mortality of shrimp fed with extracts during 14 days decreased significantly, whereas control shrimps displayed 100% mortality upon V. parahaemolyticus challenge. In summary, we propose that a diet supplemented with P. betle and P. emblica leaf extract improves the growth of shrimp, and improves their immunity as is evident from their decreased susceptibility to V. parahaemolyticus infection.