Effects of alginate oligosaccharides on growth, immunity, and nutritional quality of Pacific white shrimp, Litopenaeus vannamei

Alginate oligosaccharides (AOS), known as a functional marine oligosaccharide with multiple biological activities, were studied to evaluate their application potential in Pacific white shrimp farming. A 60-day aquaculture trial was conducted, with low polymerization degree (DP 2–5) AOS supplemented to the basal diet at 0.5 %, 1.0 %, and 1.5 %, respectively. The experimental results showed that the addition of AOS at a level of 1.0 % significantly promoted the growth and the activities of digestive-related enzymes. AOS did not change the basic nutritional components of the shrimp. However, it significantly increased the contents of umami amino acids, total amino acids, unsaturated fatty acids, linoleic acid, eicosapentaenoic acid, and docosahexaenoic acid. AOS significantly changed the intestinal microbial community structure of the shrimp, notably enhanced the activities of immunity/antioxidant-related enzymes. Furthermore, transcriptomic analysis results revealed that AOS could activate pathways related to amino acid metabolism and fatty acid metabolism, thereby enhancing the metabolic processes of relevant substances in Litopenaeus vannamei . Concurrently, AOS could also activate the immune-related pathways, which improved the shrimp’s immune function and antioxidant capacity. However, the effects of AOS varied with different addition levels. The results indicated that the addition levels of 0.5 % - 1.0 % were superior to 1.5 % in promoting the growth and health of the shrimp. This study demonstrated that AOS can improve feed utilization and boost the immune and antioxidant capacities without affecting the basic nutritional components of shrimp, which provides a theoretical basis for the development of functional feeds containing AOS. • Adding a small amount of low-polymerization (DP 2–5) algal oligosaccharides (AOS) to feed can improve shrimp growth performance. • Consumption of AOS can activate shrimp immune and antioxidant physiological responses. • AOS do not alter the basic nutritional composition of shrimp, but they affect the amino acid and fatty acid profiles. • The beneficial effects of AOS on shrimp are not positively correlated with the amount of supplementation.