Growth and Welfare of Rainbow Trout (Oncorhynchus mykiss) in Response to Graded Levels of Insect and Poultry By-Product Meals in Fishmeal-Free Diets

This study compared the nutrient-energy retention, digestive function, growth performance, and welfare of rainbow trout (ibw 54 g) fed isoproteic (42%), isolipidic (24%), fishmeal-free diets (CV) over 13 weeks. The diets consisted of plant-protein replacement with graded levels (10, 30, 60%) of protein from poultry by-product (PBM) and black soldier fly H. illucens pupae (BSFM) meals, either singly or in combination. A fishmeal-based diet was also tested (CF). Nitrogen retention improved with moderate or high levels of dietary PBM and BSFM relative to CV (p < 0.05). Gut brush border enzyme activity was poorly affected by the diets. Gastric chitinase was up-regulated after high BSFM feeding (p < 0.05). The gut peptide and amino acid transport genes were differently regulated by protein source and level. Serum cortisol was unaffected, and the changes in metabolites stayed within the physiological range. High PBM and high BSFM lowered the leukocyte respiratory burst activity and increased the lysozyme activity compared to CV (p < 0.05). The BSFM and PBM both significantly changed the relative percentage of lymphocytes and monocytes (p < 0.05). In conclusion, moderate to high PBM and BSFM inclusions in fishmeal-free diets, either singly or in combination, improved gut function and nutrient retention, resulting in better growth performance and the good welfare of the rainbow trout

Effects of rearing density on sea bass (

During 84 days, the effects of density on juvenile sea bass (Dicentrarchus labrax) (76±16 g) were studied in an experimental tank-based flow through system. Performance, stress response and resistance to virus infection were analysed under five stabilized rearing densities: 10, 20, 40, 70 and 100 kg m-3. Water quality parameters (CO2, total ammonia nitrogen and O2) were measured and maintained close to the recommended values for farmed sea bass by adjusting water renewal exchange. No significant differences were observed between density treatments, neither on stress response (cortisol) nor susceptibility to nodavirus. With regards to biological performances, the daily feed intake and specific growth rate were significantly lower in fish reared at the 100 kg m-3 density. Results on the effects of density in sea bass reared in flow through (present study) and in recirculating aquaculture systems (RAS) (Sammouth et al. 2009) were compared as a contribution to the identification of density not affecting health and welfare in farmed sea bass

Environmental hazard of yperite released at sea: sublethal toxic effects on fish

The aim of this study was to evaluate the potential toxicological effects on fish related to the leakage of yperite from rusted bomb shells dumped at sea. Both in vivo and field studies have been performed. As for the in vivo experiment, specimen of European eel were subcutaneously injected with 0.015, 0.15 and 1.5 mg/kg of yperite and sacrificed after 24 and 48 h. In the field study, specimen of Conger eel were collected from a dumping site in the Southern Adriatic Sea. The presence/absence of yperite in tissues, genotoxicity, detoxification enzymes, histological alterations and gross abnormalities were investigated. Results of the in vivo experiment showed a significant increase of EROD activity at both 24 h and 48 h. UGT activity increased significantly at 48 h post injection. An acute inflammatory response after 24 h in skin layers and muscle was observed, associated to cell degeneration and necrosis after 48 h at the highest dose. On field, comet assay revealed genotoxicity in gills of fish from the dumping site. Specimen from the dumping site showed significantly higher EROD activities compared to controls, deep ulcers and papules on skin together with liver and spleen histopathological lesions

Effects of dietary plant proteins on immune system in turbot juveniles Psetta maxima

The impact of fish meal replacement with plant proteins on fish health is still poorly investigated. This study evaluates the effects of several diets containing graded levels of a mixture of gluten meal, soybean meal and soy protein concentrate on some immune parameters of turbot juveniles. The feeding trial was carried out at the aquaculture facilities of the Veterinary University of Bologna (Cesenatico, Italy). Turbot juveniles (9.7kept at 18in 500 l recirculating tanks (in triplicate) were fed four isonitrogenous (51%) and isolipidic diets (16%) (Skretting ARC, Stavanger, NO) for 9 weeks: a reference diet of 50% fish meal (FM50), and three diets containing 35%, 20% and 5% fish meal (FM35; FM20; FM5), with a proportional amount of vegetable ingredients. At the end of the trial, blood samples and spleen tissues were collected and analyzed for serum lysozyme concentration (lysoplate assay), differential leukocyte count (blood smears/May-Grunwald Giemsa) and quantification of splenic melano-macrophage centres (MMCs) (histology/image analyzer). One-way ANOVA and c2-test were applied respectively to humoral and cellular immune parameters to test the effects of dietary treatment. Plant protein diets induced significant changes in several immune parameters in turbot juveniles. Serum lysozyme was higher in turbot fed on FM35 and FM20 diets. The percentage of circulating phagocytes, mainly neutrophils, and splenic MMCs, increased, especially in fish fed FM5 and FM20 diets. No difference was observed in lymphocyte population. The increase in blood phagocytes could be responsible for the rise in serum lysozyme and interpretable as a stress or inflammatory response. Conversely, the lower lysozyme level measured in turbot fed FM5 diet in the face of a higher number of circulating phagocytes could be interpreted as a functional impairment of these cells. The increase in MMCs may be associated with a nutritional deficit, which is more severe in fish fed FM5. Long-term feeding trials are needed in order to gain further insight into the impact of dietary plant proteins on immune function and health in turbot

Microbial assemblages for environmental quality assessment: Knowledge, gaps and usefulness in the European Marine Strategy Framework Directive

The EU Marine Strategy Framework Directive 2008/56/EC (MSFD) defines a framework for Community actions in the field of marine environmental policy in order to achieve and/or maintain the Good Environmental Status (GES) of the European seas by 2020. Microbial assemblages (from viruses to microbial-sized metazoa) provide a major contribution to global biodiversity and play a crucial role in the functioning of marine ecosystems, but are largely ignored by the MSFD. Prokaryotes are only seen as \u2018\u2018microbial pathogens,\u2019\u2019 without defining their role in GES indicators. However, structural or functional prokaryotic variables (abundance, biodiversity and metabolism) can be easily incorporated into several MSFD descriptors (i.e. D1. biodiversity, D4. food webs, D5. eutrophication, D8. contaminants and D9. contaminants in seafood) with beneficial effects. This review provides a critical analysis of the current MSFD descriptors and illustrates the reliability and advantages of the potential incorporation of some prokaryotic variables within the set of indicators of marine environmental quality. Following a cost/benefit analysis against scientific and economic criteria, we conclude that marine microbial components, and particularly prokaryotes, are highly effective for detecting the effects of anthropogenic pressures on marine environments and for assessing changes in the environmental health status. Thus, we recommend the inclusion of these components in future implementations of the MSFD