Enterocytozoon hepatopenaei (EHP) is a microsporidian parasite that infects farmed whiteleg shrimp (Litopenaeus vannamei), causing significant issues such as growth retardation, increased mortality, and economic losses in shrimp aquaculture. Various functional feed additives have been investigated to boost shrimp immunity and resilience to EHP, though with inconsistent results. Among these, phytogenic compounds have shown promise in inhibiting both aquatic and terrestrial parasites, therefore i ncorporating such compounds into shrimp diets may represent a promising practical strategy to reduce the impact of EHP infections.
This study evaluated the efficacy of a microencapsulated phytogenic blend (MPB), previously shown to suppress EHP spore germination in vitro. The experiment included four dietary treatments: (1) Negative Control (NC): basal diet only; (2) Positive Control (PC): basal diet + EHP challenge; (3) basal diet + MPB at 250 ppm + EHP challenge; and (4) basal diet + MPB at 500 ppm + EHP challenge. Shrimps (50 ind/ tank) were stocked in 350 L tanks, with six replicate tanks per treatment. The trial lasted 63 days, including a 7-day EHP exposure phase followed by 42 days of post-challenge monitoring. EHP infection was induced by oral administration of feed coated with a homogenized suspension of EHP-infected faeces. Growth performance, feed utilization, survival, and immune parameters were monitored throughout, and data were analyzed via one-way ANOVA followed by Duncan’s post-hoc test.
At the end of the 42-day post-challenge period, survival rates were as follows: NC (80.80%), PC (55.43%), MPB 250 ppm (64.13%), and MPB 500 ppm (73.19%). Survival was significantly higher in the NC group compared to all challenged groups. Among the infected treatments, shrimp fed MPB at 500 ppm showed significantly higher survival than both the PC (+32.04% R elative P ercent S urvival) and MPB 250 ppm groups. These results indicate that dietary inclusion of MPB enhances shrimp survival following EHP challenge, with 500 ppm offering the most pronounced protective effect. Nevertheless, the MPB 250 ppm dose also conferred improved survival over the challenged control.