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Increased dietary 5-hydroxytryptophan reduces fearfulness in red junglefowl hens (Gallus gallus)

Our production animals typically suffer poor welfare, which can be revealed by measuring the affective state these animals are in. Negative affective state is linked to poorer welfare, and can be measured as fearfulness. While continuing to research how to improve animal welfare, a compliment to red...

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Autores principales: Lundgren, Kristoffer Anton, Løvlie, Hanne
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Frontiers Media S.A. 2023
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10520959/
https://www.ncbi.nlm.nih.gov/pubmed/37766752
http://dx.doi.org/10.3389/fphys.2023.1213986
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author Lundgren, Kristoffer Anton
Løvlie, Hanne
author_facet Lundgren, Kristoffer Anton
Løvlie, Hanne
author_sort Lundgren, Kristoffer Anton
collection PubMed
description Our production animals typically suffer poor welfare, which can be revealed by measuring the affective state these animals are in. Negative affective state is linked to poorer welfare, and can be measured as fearfulness. While continuing to research how to improve animal welfare, a compliment to reduce negative affective state could therefore be to reduce individuals’ fearfulness, similar to how negative affective states are medicated in humans. A proposed mechanism for this is via the monoaminergic systems. This is based on previous studies across species that have linked the serotonergic system and fear-related behaviour. We here aimed to experimentally manipulate the serotonergic system in red junglefowl hens (Gallus gallus), the main ancestor of all domesticated chickens. We measured fearfulness as latency remaining immobile in a tonic immobility test, and did so both before and after our experimental manipulation. We set out to experimentally manipulate the serotonergic system via sub-chronic dietary treatment of 5-hydroxytryptophan (the precursor to serotonin). Our dietary manipulation of 5-hydroxytryptophan significantly reduced measured fearfulness in the manipulated hens, while latency in tonic immobility did not significantly change in our unmanipulated, control hens. This finding is promising since it indicates that increased tryptophan levels can be used to reduce fearfulness. Additionally, our result suggests that this can be done non-invasively via food (instead of injections), thus presenting a potentially feasible manipulation also for larger settings. Nevertheless, the serotonergic system is complex and its role in modulating behaviour in the fowl should be explored further to evaluate our findings, and more directly explored also in a production setting.
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spelling pubmed-105209592023-09-27 Increased dietary 5-hydroxytryptophan reduces fearfulness in red junglefowl hens (Gallus gallus) Lundgren, Kristoffer Anton Løvlie, Hanne Front Physiol Physiology Our production animals typically suffer poor welfare, which can be revealed by measuring the affective state these animals are in. Negative affective state is linked to poorer welfare, and can be measured as fearfulness. While continuing to research how to improve animal welfare, a compliment to reduce negative affective state could therefore be to reduce individuals’ fearfulness, similar to how negative affective states are medicated in humans. A proposed mechanism for this is via the monoaminergic systems. This is based on previous studies across species that have linked the serotonergic system and fear-related behaviour. We here aimed to experimentally manipulate the serotonergic system in red junglefowl hens (Gallus gallus), the main ancestor of all domesticated chickens. We measured fearfulness as latency remaining immobile in a tonic immobility test, and did so both before and after our experimental manipulation. We set out to experimentally manipulate the serotonergic system via sub-chronic dietary treatment of 5-hydroxytryptophan (the precursor to serotonin). Our dietary manipulation of 5-hydroxytryptophan significantly reduced measured fearfulness in the manipulated hens, while latency in tonic immobility did not significantly change in our unmanipulated, control hens. This finding is promising since it indicates that increased tryptophan levels can be used to reduce fearfulness. Additionally, our result suggests that this can be done non-invasively via food (instead of injections), thus presenting a potentially feasible manipulation also for larger settings. Nevertheless, the serotonergic system is complex and its role in modulating behaviour in the fowl should be explored further to evaluate our findings, and more directly explored also in a production setting. Frontiers Media S.A. 2023-09-12 /pmc/articles/PMC10520959/ /pubmed/37766752 http://dx.doi.org/10.3389/fphys.2023.1213986 Text en Copyright © 2023 Lundgren and Løvlie. https://creativecommons.org/licenses/by/4.0/This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
spellingShingle Physiology
Lundgren, Kristoffer Anton
Løvlie, Hanne
Increased dietary 5-hydroxytryptophan reduces fearfulness in red junglefowl hens (Gallus gallus)
title Increased dietary 5-hydroxytryptophan reduces fearfulness in red junglefowl hens (Gallus gallus)
title_full Increased dietary 5-hydroxytryptophan reduces fearfulness in red junglefowl hens (Gallus gallus)
title_fullStr Increased dietary 5-hydroxytryptophan reduces fearfulness in red junglefowl hens (Gallus gallus)
title_full_unstemmed Increased dietary 5-hydroxytryptophan reduces fearfulness in red junglefowl hens (Gallus gallus)
title_short Increased dietary 5-hydroxytryptophan reduces fearfulness in red junglefowl hens (Gallus gallus)
title_sort increased dietary 5-hydroxytryptophan reduces fearfulness in red junglefowl hens (gallus gallus)
topic Physiology
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10520959/
https://www.ncbi.nlm.nih.gov/pubmed/37766752
http://dx.doi.org/10.3389/fphys.2023.1213986
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