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Session : Génétique et Sélection; Nouveaux ingrédients et amélioration génétique : des solutions prometteuses pour améliorer les performances de croissance de la truite arc-en-ciel sur aliment végétal. 6. Journées de la Recherche Filière Piscicole

UMR BFP - Equipe BFP; Nutrition of high trophic species in aquaculture is faced with the development of sustainable plant-based diets. Insects seem particularly promising for supplementing plant-based diets. However, the complex effect of whole insect meal on fish metabolism is not well understood, and even less is known about insect meal extracts. The purpose of this work was to decipher the metabolic utilization of a plant-based diet supplemented with the gradual addition of an insect protein extract (insect hydrolysate at 0%, 5%, 10% and 15%). 1H-NMR profiling was used to assess metabolites in experimental diets and in fish plasma, liver and muscle. A significant dose-dependent increase in growth and feed efficiency with increasing insect extract amounts was observed. The incremental incorporation of the insect extract in diet had a significant and progressive impact on the profile of dietary soluble compounds and trout metabolome. The metabolites modulated by dietary insect extracts in plasma and tissues were involved in protein and energy metabolism. This was associated with the efficient metabolic use of dietary free amino acids toward protein synthesis through the concomitant supply of balanced free amino acids and energy substrates in muscle. The findings provide new insights into how the dietary food metabolome affects fish metabolism.

International audience; Fast development of the aquaculture sector in the last decades conducted to a shortage in traditional ingredients (fishmeal and fish oil) that were not anymore avaible in sufficient quantity to purvey such growing aquafeeds needs. Ingredients of plant-derived raw materials, thus started to be preferentially incorporated into aquafeed formulas, and are nowadays being routinely used in most fish feed formulas. However, the total replacement of fishmeal and fish oil has not yet been reached due to negative impacts on feed intake and feed efficiency, perturbations of metabolic and health status, impacts on flesh quality, and growth performances slowdown. Single cell protein sources such as yeast protein products could be an alternative solution to complement and mitigate detrimental effects of plant proteins. This was assessed in a 12 weeks trial in which rainbow trout (Oncorhynchus mykiss) juveniles were fed with a plant-based diet (totally devoid of fishmeal and fish oil), containing 0, 5, 10 or 15% of a protein-rich yeast fraction and microalgae as DHA source.Results indicated that a 15% protein-rich yeast fraction inclusion may upgrade growth performance of trout fed plant-based diets by improving feed conversion ratio and body nitrogen retention. Surprisingly, 5% yeast incorporation in the diet leaded to enhanced accumulation of DHA in whole body that could be linked to a higher expression of the fatty acid elongase 2. Immune status and gut health of fish were also assessed through histological analyses and transcript expression level measurements of immune-related genes in distal intestine complemented by measurement of some plasma immune-related parameters. A lower score of lymphocytes infiltrates in lamina propria of fish distal intestine was observed from 10% inclusion level of the yeast fraction and the calculated overall inflammation score was greatly reduced with 15% inclusion level. In fish fed diets containing 5% and 15% yeast fraction, a higher internal perimeter: external perimeter ratio was measured compared to fish fed the control plant-based group. Inclusion of 15% yeast fraction in the plant-based diet also lead to an increased expression of mucin 5 and claudin a compared to 5% inclusion level. A statistically negative linear correlation was revealed between plasma neutrophils proportions and dietary yeast content. Plasma lysozyme concentration was lower in trouts fed diets containing 10% and 15% yeast fraction. All together, those results revealed that inclusion of yeast in a plant-based diet enables to improve rainbow trout gut health and global immune status

Background Plant raw materials are commonly used in aquafeeds, as marine resources are unsustainable. However, full plant-based diets lead to poorer fish growth performance. Objective We aimed to understand the metabolic effects of a yeast fraction as a protein supplement in a plant-based diet and to integrate such effects with phenotypic traits as a new approach to assess the interest of this raw material. Methods Juvenile (49 g) rainbow trout (Oncorhynchus mykiss) were fed graded levels of a yeast protein-rich fraction (5% YST05, 10% YST10, 15% YST15) in a plant-based diet (PB) for 84 d. Final body weight, feed conversion ratio, and hepatosomatic and viscerosomatic indexes were measured. Plasma, liver, and muscle 1H-NMR fingerprints were analyzed with principal component analyses, and their metabolite patterns were clustered according to the yeast level to identify concomitant metabolic effects. A regression modeling approach was used to predict tissue metabolite changes from plasma fingerprints. Results In tissues, the patterns of metabolite changes followed either linear trends with the gradual inclusion of a yeast fraction (2 patterns out of 6 in muscle, 1 in liver) or quadratic trends (4 patterns in muscle, 5 in liver). Muscle aspartate and glucose (395 and 138% maximum increase in relative content compared with PB, respectively) revealing modification in energy metabolism, as well as modification of liver betaine (163% maximum increase) and muscle histidine (57% maximum decrease) related functions, indicates that the yeast fraction could improve growth in several ways. The highest correlation between measured and predicted metabolite intensities in a tissue based on plasma fingerprints was observed for betaine in liver (r = 0.80). Conclusions These findings herald a new approach to assess the plurality of metabolic effects induced by diets and establish the optimal level of raw materials. They open the way for using plasma as a noninvasive matrix in trout nutrition studies.

Résumé; Exploring the adaptation of rainbow trout metabolome to novel aquafeeds by H-NMR metabolomics. Metabolomics 2019. 15. Annual Conference of the Metabolomics Society

Résumé; Integrative 1H-NMR metabolomic investigation of the effect of alternative diets on rainbow trout plasma. 18. ISFNF International Symposium on Fish Nutrition and Feeding "40 years of research in fish nutrition"