Schizochytrium limacinum Supplementation in a Low Fish-Meal Diet Improved Immune Response and Intestinal Health of Juvenile Penaeus monodon

Abstract

The aim of the present experiment was to evaluate the effects of Schizochytrium limacinum supplementation on the immune response, gut microbiota, and health of Penaeus monodon fed a low fish-meal (FM) diet. A diet containing 25% FM was used as a control (Diet A), and three other diets were formulated to contain 15% FM and supplemented with 0, 0.75, and 1.5% S. limacinum (Diet B, C, and D, respectively). The experiment was carried out in quadruplicates (30 shrimp per replicate, average weight 1.01 ± 0.01 g), and the shrimps were fed the test diets to apparent satiation three times daily for 8 weeks. Shrimp fed diet B and D showed lower weight gain than those fed diet A. Supplementation of 0.75% S. limacinum enhanced expression of antioxidative genes (superoxide dismutase and catalase) and immuneresponse-related genes in hepatopancreas but could not affect the gene expression of immune deficiency in hepatopancreas and Tube in the intestine. A low FM diet induced endoplasmic reticulum swelling of the intestinal epithelial cells, which was alleviated by S. limacinum supplementation. Ultra-performance liquid chromatography coupled with quadrupole time of flight mass spectrometry was employed to analyze the changes of hemolymph metabolomics, 49 significantly different metabolites were identified, and lysoPCs, deoxyinosine, inosine, and highly unsaturated fatty acids were lower in fish fed with low FM diets. Intestinal microbial diversity was lower in shrimp fed Diet B than those fed the control diet. Dietary supplementation of 0.75% S. limacinum increased intestinal microbial diversity of shrimp and decreased the ratio of pathogenic bacterium (Thalassotalea and Tenacibaculum). These results indicated that supplementing S. limacinum into a low FM diet improves the growth performance, immune response, and intestinal health of P. monodon. The optimum inclusion level of seems to be 0.75% of diet.

Low Dietary Fish Meal Induced Endoplasmic Reticulum Stress and Impaired Phospholipids Metabolism in Juvenile Pacific White Shrimp, Litopenaeus vannamei

“…Thirty six shrimp hemolymph samples for all treatments were analyzed by UPLC-Q/TOF-MS in this research to study the lipid profiles in FM25, FM15 and FM5, 12 for each treatment. The method was described by Xie et al (2020) . Briefly, 400 μL acetonitrile/methanol (9:1) was mixed with 100 μL hemolymph and vortexed for 30 s. The mixture was centrifuged at 13, 000 g and 4°C for 10 min, 200 μL supernatant was used for UPLC-Q/TOF-MS analysis.…”

“…Chromatographic separation was carried out at 40°C on an ACQUITY HSS T3 1-class column (2.1 × 100 mm, 1.8 μm, Waters). The method of the UPLC-Q/TOF-MS analysis was same as Xie et al (2020) .…”

“…Another three midgut per tank were collected for transmission eletron microscopy (TEM) examination. The method was described by Zhang et al (2012) and Xie et al (2020), briefly, samples were fixed in 2.5% glutaraldehyde solution (4 • C), then fixed in 1% osmium tetroxide (OsO4) for 1 h, dehydrated in a graded series of ethyl alcohol, finally embedded with resin. Ultrathin sections (90 nm) were placed on copper grids and were stained with saturated uranyl acetate solution for 30 min, rinsed with distilled water and poststained with lead citrate for 30 min.…”

“…Thirty six shrimp hemolymph samples for all treatments were analyzed by UPLC-Q/TOF-MS in this research to study the lipid profiles in FM25, FM15 and FM5, 12 for each treatment. The method was described by Xie et al (2020). Briefly, 400 µL FIGURE 3 | The effect of fish meal levels on energy metabolism of white shrimp.…”

“…Excessive substitution of FM generally led to poor growth performance, which may because the nutrient-sensing and metabolism of fish and shrimp are changed when fed a low FM diet ( Wang et al, 2016 ; Xu et al, 2016 ). Besides growth retardation, shrimp health were impaired when fed a low FM diet ( Wu et al, 2009 ; Xie et al, 2016 , 2020 ), figure out the potential mechanism would be helpful in further reducing FM in aquafeeds, not only in the feed of L. vannamei , but also in the feeds of many carnivorous fish. The wide nutritional differences between FM and other ingredients make it hard to find the key metabolism pathways and biomarkers which responsible for the negative effects brought by low dietary FM.…”