Effect of brown seaweeds on Pacific white shrimp growth performance, gut morphology, digestive enzymes activity and resistance to white spot virus

This work aimed to evaluate growth performance, gut histology, digestive enzyme activity and resistance to challenge with White Spot Syndrome Virus (WSSV) of Litopenaeus vannamei fed 0.5, 2 and 4% of dry biomass from the brown seaweeds Sargassum filipendula and Undaria pinnatifida. Shrimp (4.23 ± 0.15 g) were reared for 38 days in 800 L tanks (40 animals per tank) in triplicate under constant aeration (O2 > 5 mg L−1), controlled temperature (29.06 ± 0.32 °C) and 100% daily water exchange (static). Animals were fed five times per day, and the amount of feed was calculated in accordance with a pre-established feed conversion rate method. To estimate survival and growth, all animals from each tank were weighed and counted every week. At the end of the experiment, the hepatopancreas from each of six shrimp per treatment was collected to assess the digestive enzymes, and the anterior abdominal segment from each of four shrimp per treatment was isolated to evaluate the gut histology. For WSSV challenge, 40 animals per treatment were infected and kept for 72 h to determine mortality. Growth performance was not affected by seaweed addition in the diet. However, the lowest level of both seaweeds increased shrimp gut epithelial surface for nutrient absorption, and all levels of S. filipendula and 4% of U. pinnatifida increased amylase activity, while lipase activity was only stimulated by 4% of U. pinnatifida. Proteolytic enzymes were not affected by the addition of dietary seaweed. Additionally, 4% of U. pinnatifida resulted in lower mortality after WSSV challenge (48%) compared to control (74%). Therefore, seaweed addition improved shrimp digestive capacity and resistance to WSSV challenge, but without impairing growth performance.