Investigation of the effects of cup plant (Silphium perfoliatum L.) on the growth, immunity, gut microbiota and disease resistance of Penaeus vannamei

Shrimp White Spot Viral Infections Are Attenuated by Organic Acids by Regulating the Expression of HO-1 Oxygenase and β-1,3-Glucan-Binding Protein

The absence of efficient on-farm interventions against white spot syndrome viral (WSSV) infections can cause significant economic losses to shrimp farmers. With this exploratory study we aimed to test, both in vitro and in vivo, the efficacy of an organic acid mixture (Aq) against WSSV infections in shrimp. In vitro, using shrimp gut primary cells (SGP), 2% Aq significantly reduced WSSV infection and the amounts of H2O2 released but had no impact on CAT and SOD expression. In vivo, in a shrimp challenge test, 2% Aq significantly downregulated the expression of proteins involved in WSSV virulence, such as the lipopolysaccharide-β-1,3-glucan-binding protein (LGBP) and the TLR signalling pathway (LvECSIT), and increased the expression of HO-1 oxygenase. Additionally, at 2% Aq, the expression of the digestive-related enzyme carboxypeptidase B was upregulated in the gut, alongside a significant decrease in IL-22 expression, a cytokine usually increased during WSSV infection in shrimp. A low mortality rate (7.33%) was recorded in infected shrimp treated with 2% Aq compared to the 96.66% mortality in the absence of Aq. The peritrophic membrane (PM) was proven essential to ensure Aq efficacy, as the infected and treated PM deficient shrimp (PM-) had a mortality rate of 27.8%, compared to only 9.34% mortality in the infected shrimp at 2% Aq and in the presence of PM (PM+). Aq significantly increased the expression of mucin-1, mucin-2, mucin-5AC, mucin-5B, and mucin-19 in both PM+ and PM- shrimp. Conclusively, organic acid in mixtures can protect farmed shrimp against WSSV infection and increase their survivability through a mediated gut health effect which includes resistance to oxidative stress and improved immunity.

Safety evaluation and effects of dietary phlorotannins on the growth, health, and intestinal microbiota of Litopenaeus vannamei

Phlorotannins are phenolic compounds with diverse biological activities, yet their efficacy in aquatic animals currently remains unclear. This investigation scrutinized the influence of phlorotannins on the growth, immunity, antioxidant capacity, and intestinal microbiota in Litopenaeus vannamei, concurrently evaluating the potential adverse effects of phlorotannins on L. vannamei. A base diet without phlorotannins supplementation was used as a control, and 4 groups of diets with different concentrations (0, 0.5, 1.0, 2.0 g kg-1) of phlorotannins were formulated and fed to juvenile shrimp (0.25 ± 0.01 g) for 60 days followed by a 24-h challenge with Vibrio parahaemolyticus with triplicate in each group. Compared with the control, dietary 2.0 g kg-1 phlorotannins significantly improved the growth of the shrimp. The activities of enzymes related to cellular immunity, humoral immunity, and antioxidants, along with a notable upregulation in the expression of related genes, significantly increased. After V. parahaemolyticus challenge, the cumulative survival rates of the shrimp demonstrated a positive correlation with elevated concentrations of phlorotannins. In addition, the abundance of Bacteroidetes and functional genes associated with metabolism increased in phlorotannins supplementation groups. Phlorotannins did not elicit any detrimental effects on the biological macromolecules or histological integrity of the hepatopancreas or intestines. Simultaneously, it led to a significant reduction in malondialdehyde content. All results indicated that phlorotannins at concentrations of 2.0 g kg-1 can be used as safe feed additives to promote the growth, stimulate the immune response, improve the antioxidant capacity and intestinal health of L. vannamei, and an protect shrimp from damage caused by oxidative stress.

Effects of Lactobacillus plantarum Ep-M17 on growth, immunity and intestinal microbiota of Penaeus vannamei under Microcystin-LR stress

Microcystins (MCs) are biologically active cyclic heptapeptide compounds released by cyanobacteria in water bodies, and MC-LR is one of the most widespread and toxic isoforms. It frequently poses a serious threat to Penaeus vannamei aquaculture. Our previous study revealed that the supplementation of Lactobacillus plantarum Ep-M17 has a probiotic effect on P. vannamei health and whether Ep-M17 can alleviate the stressful effects of MC-LR on shrimp remains unclear. Therefore, in the present work, shrimp were fed MC-LR alone or combined with Ep-M17 for six weeks, and then evaluated the effects on histology, enzyme activity, gene expression, and intestinal flora. The results showed that MC-LR stress lead to slow growth and reduced survival rates in shrimp. However, feeding Ep-M17 significantly increased both the growth rate and survival rate. Meanwhile, MC-LR stress caused severe tissue damage in the hepatopancreas and intestines of shrimp, but Ep-M17 significantly reduced the toxic effects and protected the integrity of these tissues. Additionally, Ep-M17 significantly enhanced the activities of antioxidant enzymes and digestive enzymes, and induced higher expression of immune-related genes, thereby promoting the digestive and immune responses in shrimp. Furthermore, MC-LR stress disrupted the intestinal flora in shrimp intestines, while the use of Ep-M17 significantly increased the abundance of immune- and metabolism-related bacteria and inhibited the growth of pathogenic bacteria to maintain intestinal flora balance and intestinal health. In conclusion, our results indicate that Ep-M17 can reduce the toxic effect of MC-LR on shrimp and has a positive function in the prevention and control of shrimp diseases caused by MC-LR.