The global shrimp farming industry is increasingly challenged by diseases, with Hepatopancreatic Microsporidiosis (HPM) caused by the microsporidian Enterocytozoon hepatopenaei (EHP) emerging as a significant concern. HPM, also causes symptoms similar to acute hepatopancreatic necrosis disease (AHPND). HPM currently lacks a pharmaceutical treatment and leads to significant economic and production losses. However, nutritional strategies may offer a promising solution to mitigate EHP infection and associated growth retardation.We hypothesized that Krill Meal (KM) could be an effective component of a nutritional strategy to alleviate EHP infection, given its rich content of high-quality nutrients, particularly phospholipids and long-chain polyunsaturated fatty acids, such as EPA and DHA.
To test this hypothesis, a trial was conducted to evaluate the efficacy of dietary KM incorporation at three different inclusion levels (3%, 6%, and 9%) on the growth and survival of Penaeus vannamei shrimp challenged with EHP, comparing results to infected and non-infected control groups. Shrimp, with an average weight of 4-5g, were sourced from a single farm and reared in Fiber Reinforced Plastic (FRP) tanks in four replicates, where they were fed their respective test diets for 8 weeks. Additionally, two more groups were included in the study, where shrimp were fed either a control diet or a 6% KM inclusion for 25 days before being infected with EHP by feeding the minced hepatopancreatic tissue from EHP-infected shrimp.
After 8 weeks of feeding, all KM diet groups showed better growth, FCR and survival rates compared to the control group, as shown in Figures 1 and 2.
To further examine the impact of KM on hepatopancreatic function, histological analysis was performed, revealing a significantly higher number of R cells in shrimp fed KM-supplemented diets, indicating the enhanced functional capacity of the hepatopancreas in these groups.
Additionally, a notable reduction in EHP copy number was observed in KM-fed shrimp at 6% and 9% inclusion levels compared to the control group, indicating an improved ability to cope with EHP infection (Figure 3).
To gain deeper insights, proteomic analysis was conducted to assess changes in protein expression and related biochemical pathways associated with KM inclusion. The findings revealed a more regulated and targeted immune response to EHP in shrimp fed with KM, aligning with the observed improvements in survival and growth performance.