A commercial macroalgae extract in a plant-protein rich diet diminished saturated fatty acids of Oncorhynchus mykiss Walbaum fillets

Seaweeds are considered novel feed ingredients, nutraceutical compounds and source of pigments and proteins. They appear to possess bioactive properties, such as hypolipidemic, antioxidant and immune-stimulative actions; furthermore, their proteins are considered just as nutritious as terrestrial vegetables. In the present work, rainbow trout (Oncorhynchus mykiss Walbaum) was fed for 95 days with three diets: a fishmeal-based positive control diet (C+), a vegetable protein-based negative control diet (C−) and a diet similar to C − where 5% of soybean concentrate was replaced by a commercial blend of seaweeds (T). The monitored parameters were fish performance, physical and marketable characteristics, fillet oxidative status and fatty acid content. The estimated indices of enzyme activities involved in lipid metabolism were calculated. Fish performances were reduced in C − and T fish; C − and T fillet fatty acid (FA) profiles globally showed the same pattern and were distinct from C+, i.e. with a lower content of polyunsaturated FAs and a higher content of monounsaturated and polyunsaturated n6 FAs; contrarywise, saturated FAs were significantly lower in T group in comparison to the other two groups (p <.01). The estimated indices of enzyme activity highlighted differences between dietary groups; desaturase activities of C18 and n3 FAs were higher in T in comparison to C− (p <.001). A slight impoverishment of antioxidant activity was found in T compared to C + group. Dietary seaweeds seemed to be capable of influencing fillet FA composition as well as the activity of enzymes related to lipid metabolism. Further studies in this regard are encouraged.Highlights Seaweeds are novel feed ingredients with nutraceutical properties Saturated fatty acids of rainbow trout fillets were lowered by seaweed inclusion in the diet Estimated desaturase activities of C18 and n3 fatty acids were higher in seaweed-fed trout

Physico-Chemical Traits of Raw and Cooked Fillets of Rainbow Trout (Oncorhynchus Mykiss) from Different Strains and Farms

Fillets and cooking yields, water holding capacity, textural properties, colour, proximate composition, collagen and fatty acids of five strains (IT1, IT2, IT3, USA, UK) of rainbow trout, Oncorhynchus mykiss, reared in three farms (F1, F2, F3), were measured before and after cooking. Physico-chemical parameters of the strains greatly differed both in raw and cooked state. IT2 and USA recorded the highest yields. IT2 distinguished from the other strains, showing lowest values of hardness, chewiness, gumminess and springiness. It also had brighter and less pigmented flesh with low fat, mainly in the raw state. USA strain showed the most valuable traits in terms of texture and colour, and had higher fat and collagen content in flesh. The physico-chemical profile of each strain was differently modified by cooking. USA strain maintained a positive texture and colour profile after cooking and its quality was the best

Polyhydroxyalkanoated-Rich Microbial Cells from Bio-Based Volatile Fatty Acids as Potential Ingredient for Aquaculture Feed

In this study, the production of polyhydroxyalkanoated PHA-rich microbial biomass as a novel feed additive in aquaculture was investigated at a lab-scale. Bio-based volatile fatty acids (VFAs), obtained from the acidogenic fermentation of agricultural residues in existing anaerobic digestion plants, were used as carbon and energy to cultivate the PHA-rich microbial biomass. The experimental activities were carried out using Thauera sp. Sel9 as pure strain, which was grown in a continuous stirred-tank reactor (CSTR) operated at three different hydraulic retention times (HRT). The highest productivity obtained of biomass cells was 0.69 g/L day, operating at one day HRT while the observed PHAs production yield was 0.14 gPHA/g soluble COD removed. At these conditions, the PHA concentration in the microbial cells was 41%. Although the sulfur amino acids were available at high concentrations and above the typical concentration found in fishmeal, the amino acids profile of the obtained biomass revealed a lack of histidine and threonine. A preliminary economic analysis showed that the production of a novel source of feed additive from the conversion of agro-residues could give higher benefits in terms of revenues compared to the production of biogas production through anaerobic digestion

Processed Animal Proteins from Insect and Poultry By-Products in a Fish Meal-Free Diet for Rainbow Trout: Impact on Intestinal Microbiota and Inflammatory Markers

Sustainability of aquaculture is tied to the origin of feed ingredients. In search of sustainable fish meal-free formulations for rainbow trout, we evaluated the effect of Hermetia illucens meal (H) and poultry by-product meal (P), singly (10, 30, and 60% of either H or P) or in combination (10% H + 50% P, H10P50), as partial replacement of vegetable protein (VM) on gut microbiota (GM), inflammatory, and immune biomarkers. Fish fed the mixture H10P50 had the best growth performance. H, P, and especially the combination H10P50 partially restored \u3b1-diversity that was negatively affected by VM. Diets did not differ in the Firmicutes:Proteobacteria ratio, although the relative abundance of Gammaproteobacteria was reduced in H and was higher in P and in the fishmeal control. H had higher relative abundance of chitin-degrading Actinomyces and Bacillus, Dorea, and Enterococcus. Actinomyces was also higher in H feed, suggesting feed-chain microbiome transmission. P increased the relative abundance of protein degraders Paeniclostridium and Bacteroidales. IL-1\u3b2, IL-10, TGF-\u3b2, COX-2, and TCR-\u3b2 gene expression in the midgut and head kidney and plasma lipopolysaccharide (LPS) revealed that the diets did not compromise the gut barrier function or induce inflammation. H, P, and H10P50 therefore appear valid protein sources in fishmeal-free aquafeeds

Towards the Identification of a Suitable Commercial Diet for Carpione (Salmo carpio, Linnaeus 1758): A Multidisciplinary Study on Fish Performances, Animal Welfare and Quality Traits

SIMPLE SUMMARY: Carpione (Salmo carpio, Linnaeus 1758) is an endangered precious endemism of Lake Garda (Northern Italy), the largest Italian lake. To date, several bottlenecks about its culture remain unsolved, including the identification of a proper growth-out diet. In the present study, four different grossly isolipidic, isoproteic, and isoenergetic diets containing ingredients from different origins were used for S. carpio culture. Specifically, a diet largely based on marine ingredients, and currently used for carpione farming, was used as control. Three other diets were formulated in order to include relevant percentages of vegetable ingredients or processed animal proteins (at two different inclusion levels). After a three-month feeding trial, fish zootechnical performances, welfare, and flesh quality were evaluated through a multidisciplinary approach, including histology, gene expression, chemical analysis, and Fourier transform infrared spectroscopy (FTIR). This study provided the first insights on carpione physiological responses to different commercial dietary formulations. ABSTRACT: Carpione (Salmo carpio, Linnaeus 1758) is an endangered precious endemism of Lake Garda (Northern Italy), the largest Italian lake. To date, several bottlenecks about its culture remain unsolved, including the identification of a proper growth-out diet. The aim of the present study was to test four different grossly isolipidic, isoproteic, and isoenergetic diets in which the main ingredients had a different origin. Specifically, a diet currently used by local farmers for carpione culture, largely based on marine ingredients, was used as control (CTRL), while the other three diets were formulated by partially replacing marine ingredients with plant ones (VEG) or with different percentages of processed animal proteins (PAP1 and PAP2). The feeding trial was run in triplicate, over a three-month period. No significant differences in growth performance among the experimental groups were observed. However, remarkable histological alterations and inflammatory markers upregulation were observed in VEG group, while PAP inclusion played a role in attenuating inflammation and improving nutrient uptake. Fillet analyses highlighted significant differences in marketable traits and flesh fatty acid composition among the experimental groups, including the reduction of polyunsaturated fatty acids related to PAPs inclusion. In conclusion, PAPs used in the present study promoted S. carpio gut health and absorption capacity, while further studies are required to maintain proper quality traits of the final product

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

Ectopic stem cell niches sustain rainbow trout (Oncorhynchus mykiss) intestine absorptive capacity when challenged with a plant protein-rich diet

To develop more sustainable feed formulations, it is important to assess in detail their effect on gut function and health. We previously described the specific organization of the epithelial and stromal components of the intestinal stem cell niche (ISCN), in rainbow trout (RT) under actual farming conditions. In the present work, we used our previous observation, for performing a comparative analysis between a control diet (CF) and an experimental vegetable-based diet (CV) under a new perspective. We correlated diet-induced changes of the morphology and the absorptive capability of the RT mucosa with modifications of the ISCN. Histological analysis confirmed that CV diet caused a mucosa remodeling, characterized by the generation of accessory branches sprouting from the middle of the proximal intestine folds, determining a significant increase of the luminal surface. The newly-formed structures showed positivity for PepT1, Sglt-1, and Fabp2 indicating their active role in small molecule absorption. However, the cells lining the base of the new branches expressed both epithelial (sox9) and stromal (pdgfrα and foxl1) stem cell markers, rather than the expected markers of fully differentiated cells. Our results suggest that a nutritional challenge results in the formation of an ectopic ISNC at the middle of the intestinal folds that sustains the formation of functional collateral branches, presumably to compensate for the reduced intestinal absorption. Overall, these data highlight, for the first time, the plasticity of the ISCN and its possible role in compensating intestinal functions in response to challenging conditions

Is it possible to cut down fishmeal and soybean meal use in aquafeed limiting the negative effects on rainbow trout (Oncorhynchus mykiss) fillet quality and consumer acceptance?

Poultry by-products (PBM) and Hermetia illucens prepupae meal (HM) are promising alternative protein sources for aquafeeds, being palatable, nutritious, and/or cost-effective, in addition to fostering circular economy. Their inclusion in rainbow trout (Oncorhynchus mykiss) feeds, although not detrimental for growth and wellbeing, leads to a decreased fatty acid (FA) quality, specifically, a decreased polyunsaturated FA content. The present study assessed the effect of five different diets on rainbow trout's biometric, marketable, and physical traits, oxidative status, fillet nutritional quality (of fresh and of 60-day stored fillets) and consumers' liking. The diets tested were: i) a positive-control diet, based on fishmeal (CF); ii) a plant protein-based diet (CV) resembling current commercial diets, used as additional control; 60% of the vegetable proteins were substituted with either iii) PBM (P60), iv) HM (H60) or v) both PBM and HM (H10P50). The principal component analysis considering all parameters showed two neat clusters, one grouping CF samples, the other grouping the rest of the samples. Specifically, hepatosomatic index and colour were significantly altered by the different administered diets. The most evident differences between dietary treatments were found in the FA profile, with CF fish showing a distinct FA profile in comparison to the other groups. Although the highest eicosapentaenoic and docosahexaenoic acid contents were found in CF group, the total polyunsaturated FA content was not significantly different between the dietary treatments, as linoleic and linolenic acids were the lowest in the CF fillets (p < 0.001). Storage seemed to exacerbate the differences found immediately after slaughter. As a consequence of the FA profile, conjugated dienes were significantly (p < 0.05) higher in the CF group compared to all the others. MDA-eq. content, although unaffected by diet at day 0, was higher (p < 0.01) after 60 days of storage in the CF group compared to H60, P60, and H10P50 fillets. Consumer likings were favourable and not statistically different between the dietary groups. Only 20% of the consumers criticised the gustative attributes of P60 and H10P50, while almost 25% of them criticised CF, CV, and H60. In summary, the P60, H60 and H10P50 diets were not less than the commercial-like CV diet. Combining PBM and HM showed positive results and needs further studies. Improving the n-3/n-6 ratio remains a priority to be addressed when formulating aquafeeds with innovative ingredients