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Effect of glycerol feed-supplementation on seabass metabolism and gut microbiota


Dietary glycerol supplementation in aquaculture feed is seen as an alternative and inexpensive way to fuel fish metabolism, attenuate metabolic utilization of dietary proteins and, subsequently, reduce nitrogen excretion. In this study, we evaluated the impact of dietary glycerol supplementation on nitrogen excretion of European seabass (Dicentrarchus labrax) and its effects on metabolite profile and bacterial community composition of gut digesta. These effects were evaluated in a 60-day trial with fish fed diets supplemented with 2.5% or 5% (w/w) refined glycerol and without glycerol supplementation. Nuclear magnetic resonance spectroscopy and high-throughput 16S rRNA gene sequencing were used to characterize the effects of glycerol supplementation on digesta metabolite and bacterial community composition of 6-h postprandial fish. Our results showed that ammonia excretion was not altered by dietary glycerol supplementation, and the highest glycerol dosage was associated with significant increases in amino acids and a decrease of ergogenic creatine in digesta metabolome. Concomitantly, significant decreases in putative amino acid degradation pathways were detected in the predicted metagenome analysis, suggesting a metabolic shift. Taxon-specific analysis revealed significant increases in abundance of some specific genera (e.g., Burkholderia and Vibrio) and bacterial diversity. Overall, our results indicate glycerol supplementation may decrease amino acid catabolism without adversely affecting fish gut bacterial communities.

Key points

• Glycerol can be an inexpensive and energetic alternative in fish feed formulations.

• Glycerol did not affect nitrogen excretion and gut bacteriome composition.

• Glycerol reduced uptake of amino acids and increased uptake of ergogenic creatine.

• Glycerol reduced putative amino acid degradation pathways in predicted metagenome.

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This study was funded by Fundação para a Ciência e Tecnologia (FCT; Portugal) through national funds with co-funding from European Regional Development Fund (ERDF), within the Portugal 2020 Partnership Agreement, and COMPETE 2020 [research grant to IV (POCI-01-0145-FEDER-016828-PTDC/CVT-NUT/2851/2014) and individual grant to MP through Centro2020 (ReNATURE; Centro-01-0145-FEDER-000007)]; and by MAR2020, Operational Programme for the European Maritime and Fisheries Fund (EMFF) within the project AquaHeal (MAR-02.01.01-FEAMP-0031). This study was also financially supported by Strategic Funding of research units [UID/AMB/50017/2019 for CESAM, UID/BIA/04004/2019 for CFE and UID/Multi/04423/2019 for CIIMAR], which is co-funded by national funds and ERDF within the PT2020 Partnership Agreement and Compete 2020.

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Authors and Affiliations



IV, LM, and ROAO conceived the idea and designed the experimental trial. AL, FJRC, and NCMG analyzed the microbiome dataset. IV, MP, and LCT analyzed the metabolome dataset. All authors contributed to writing of the manuscript and gave final approval for publication.

Corresponding author

Correspondence to N. C. M. Gomes.

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The authors declare that they have no conflict of interest.

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All applicable international, national, and/or institutional guidelines for the care and use of animals were followed. This article does not contain any studies with human participants performed by any of the authors.

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Louvado, A., Coelho, F.J.R.C., Palma, M. et al. Effect of glycerol feed-supplementation on seabass metabolism and gut microbiota. Appl Microbiol Biotechnol 104, 8439–8453 (2020).

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  • 1H-NMR
  • Creatinine
  • Metabolomics
  • Chyme
  • Dicentrarchus labrax