Impact of Combined Supplementation with Mannan Oligosaccharide (MOS) and Nucleotides on the Immune Response of Pacific White Shrimp (Penaeus vannamei) Challenged with Infectious Myonecrosis Virus (IMNV)

Abstract Viral infections such as Infectious Myonecrosis Virus (IMNV) continue to have a major influence on shrimp aquaculture productivity. The current study examined the effects of food supplementation with mannan oligosaccharides (MOS) and nucleotides (NT), both alone and in combination, on the immune response, intestinal morphology, and IMNV resistance in juvenile Penaeus vannamei. Shrimp were fed for 30 days with one of the following diets: (i) 1 g/kg of a commercial MOS-based product (Hypergen®, ~ 54% MOS), (ii) 1 g/kg of a commercial nucleotide-based product (Biotide Extra®, ~ 30% NT), and (iii) a combination of both products at 1 g/kg each (totaling 2 g/kg). These translate into estimated quantities of active compounds in the combination treatment of 0.27 g/kg + 0.15 g/kg, 0.3 g/kg NT, and 0.54 g/kg MOS, respectively. All shrimp received an intramuscular injection of IMNV following the feeding period. Despite producing the highest total hemocyte count, the combination treatment (NM) did not demonstrate any synergistic effect (17.78%), whereas the MOS (30.56%) and NT (26.67%) groups had greater post-challenge survival rates than the control (15.56%). By increasing villus height, dietary MOS also enhanced intestinal morphology. According to the analysis, MOS or NT by itself may improve P. vannamei's innate immune responses and resistance to IMNV, even if no additive impact was shown at the tested combination levels. To maximize dosage plans and to investigate potential interactions between these functional feed additives, more research is advised.