Transmission of the mare’s hindgut microbiota and its fibrolytic function to the foal and its effect on associated health parameters

Started in september 2025

Funding: industry-oriented doctoral programme (Cifre), with Lab To Field company

Supervisors: Pauline Grimm (Lab To Field) & Gabriele Sorci (Laboratoire Biogéosciences)

Abstract

In adult horses, structural carbohydrates in plant cells (fiber) are the main source of energy. Since horses do not have digestive enzymes capable of breaking down this fiber, it is catabolized exclusively by microorganisms in the hindgut. Fibrolytic bacteria, which hydrolyze fiber, are keystone species in the microbiota (Julliand and Grimm, 2016). They are few in number but support the breakdown and fermentation of fiber into short-chain fatty acids. Short-chain fatty acids are energy substrates absorbed into the bloodstream at the intestinal mucosa and cover more than half of the energy requirements of horses (Vermorel and Martin-Rosset, 1997).

The microbiota is a component of the hindgut ecosystem and is closely related to intestinal parasites and the host’s mucosa. The microbiota and intestinal parasites interact reciprocally, notably by modifying the abiotic parameters of the ecosystem and exploiting their respective ecological niches (Walshe et al., 2020). These two components are also in constant dialogue with the immune system, modulating and being modulated by the host’s immune responses (Bancroft et al., 2012; Walshe et al., 2020).

Homeostasis of the intestinal ecosystem is essential for equine health. An imbalance in any one component of the microbiota-parasites-mucosa triad can lead to an imbalance in the entire ecosystem. Dysbiosis of the microbiota (Julliand and Grimm, 2017) and a heavy parasite load (Khan et al., 2015) are risk factors for fatal intestinal diseases in horses, such as colic and diarrhoea. Impaired immunoregulation can lead to inflammation of the intestinal barrier, resulting in poor nutrient absorption and increased translocation of pathogens and toxins (Iacob and Iacob, 2019).

The establishment of the intestinal ecosystem begins during fetal life and continues to mature during the first months of the foal’s life. The intestinal barrier and microbiota develop simultaneously. The implantation of microorganisms stimulates immunity, and in turn, immunity shapes the composition of the microbiota that becomes established (Weström et al., 2020). It is now well established that the mare’s microbial communities are transmitted to the foal in utero via the amniotic fluid and postnatally via lactation and coprophagia (Mols et al., 2020). Notably, fibrolytic communities are transmitted during the first two months of the foal’s life via coprophagia (Faubladier et al., 2013; Pyles et al., 2023). Nevertheless, the vertical transmission of the fibrolytic function carried by the mare’s microbiota remains poorly understood.

The health of the foal and, more broadly, of the future adult horse could therefore be partly determined by the microbiota transmitted by the mare. The first objective of this PhD is to assess the extent to which the fibrolytic function carried by the maternal microbiota is transmitted to the foal, and its persistence. The second objective is to study the interrelationships between the three components of the microbiota-parasites-mucosa triad and to highlight the factors that influence the homeostasis of the intestinal ecosystem. The third objective is to study the extent to which modulation of the maternal microbiota via diet can promote homeostasis in the foal’s intestinal ecosystem.

References
Bancroft et al., 2012. Trends Parasitol 28, 93–98 – Faubladier et al., 2013. Br J Nutr 110, 1040–1052 – Iacob and Iacob, 2019. Front Microbiol 10, 1676 – Julliand and Grimm, 2017. J Equine Vet Sci 52, 23–28 – Julliand and Grimm, 2016. J Anim Sci 94, 2262–2274 – Khan et al., 2015. J Anim Plant Sci 25, 1–9 – Mols et al., 2020. Anim Prod Sci 60, 2080 – Pyles et al., 2023. Animals 13, 2718 – Vermorel and Martin-Rosset, 1997. Livest Prod Sci 47, 261–275 – Walshe et al., 2020. Animals 10, 2309 – Weström et al., 2020. Front Immunol 11

Keywords

gut microbiota ; foal ; intestinal mucosa ; parasitism ; fibrolysis ; vertical transmission

Thesis advisory panel

Thierry Boulinier, CNRS, Centre d’écologie fonctionnelle et évolutive, université de Montpellier
Pierre Lapaquette, Université Bourgogne Europe, UMR PAM, équipe AFIM
Tanguy Hermange, Centre hospitalier vétérinaire équin du Livet

extrait:

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titre:

Transmission du microbiote du gros intestin et de sa fonction fibrolytique de la jument au poulain et effet sur les paramètres de santé associés

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Marchal

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Transmission of the mare’s hindgut microbiota and its fibrolytic function to the foal and its effect on associated health parameters

Started in september 2025

Funding: industry-oriented doctoral programme (Cifre), with Lab To Field company

Supervisors: Pauline Grimm (Lab To Field) & Gabriele Sorci (Laboratoire Biogéosciences)

 

Abstract

In adult horses, structural carbohydrates in plant cells (fiber) are the main source of energy. Since horses do not have digestive enzymes capable of breaking down this fiber, it is catabolized exclusively by microorganisms in the hindgut. Fibrolytic bacteria, which hydrolyze fiber, are keystone species in the microbiota (Julliand and Grimm, 2016). They are few in number but support the breakdown and fermentation of fiber into short-chain fatty acids. Short-chain fatty acids are energy substrates absorbed into the bloodstream at the intestinal mucosa and cover more than half of the energy requirements of horses (Vermorel and Martin-Rosset, 1997).

The microbiota is a component of the hindgut ecosystem and is closely related to intestinal parasites and the host's mucosa. The microbiota and intestinal parasites interact reciprocally, notably by modifying the abiotic parameters of the ecosystem and exploiting their respective ecological niches (Walshe et al., 2020). These two components are also in constant dialogue with the immune system, modulating and being modulated by the host's immune responses (Bancroft et al., 2012; Walshe et al., 2020).

Homeostasis of the intestinal ecosystem is essential for equine health. An imbalance in any one component of the microbiota-parasites-mucosa triad can lead to an imbalance in the entire ecosystem. Dysbiosis of the microbiota (Julliand and Grimm, 2017) and a heavy parasite load (Khan et al., 2015) are risk factors for fatal intestinal diseases in horses, such as colic and diarrhoea. Impaired immunoregulation can lead to inflammation of the intestinal barrier, resulting in poor nutrient absorption and increased translocation of pathogens and toxins (Iacob and Iacob, 2019).

The establishment of the intestinal ecosystem begins during fetal life and continues to mature during the first months of the foal's life. The intestinal barrier and microbiota develop simultaneously. The implantation of microorganisms stimulates immunity, and in turn, immunity shapes the composition of the microbiota that becomes established (Weström et al., 2020). It is now well established that the mare's microbial communities are transmitted to the foal in utero via the amniotic fluid and postnatally via lactation and coprophagia (Mols et al., 2020). Notably, fibrolytic communities are transmitted during the first two months of the foal's life via coprophagia (Faubladier et al., 2013; Pyles et al., 2023). Nevertheless, the vertical transmission of the fibrolytic function carried by the mare's microbiota remains poorly understood.

The health of the foal and, more broadly, of the future adult horse could therefore be partly determined by the microbiota transmitted by the mare. The first objective of this PhD is to assess the extent to which the fibrolytic function carried by the maternal microbiota is transmitted to the foal, and its persistence. The second objective is to study the interrelationships between the three components of the microbiota-parasites-mucosa triad and to highlight the factors that influence the homeostasis of the intestinal ecosystem. The third objective is to study the extent to which modulation of the maternal microbiota via diet can promote homeostasis in the foal's intestinal ecosystem.

References
Bancroft et al., 2012. Trends Parasitol 28, 93–98 - Faubladier et al., 2013. Br J Nutr 110, 1040–1052 - Iacob and Iacob, 2019. Front Microbiol 10, 1676 - Julliand and Grimm, 2017. J Equine Vet Sci 52, 23–28 - Julliand and Grimm, 2016. J Anim Sci 94, 2262–2274 - Khan et al., 2015. J Anim Plant Sci 25, 1–9 - Mols et al., 2020. Anim Prod Sci 60, 2080 - Pyles et al., 2023. Animals 13, 2718 - Vermorel and Martin-Rosset, 1997. Livest Prod Sci 47, 261–275 - Walshe et al., 2020. Animals 10, 2309 - Weström et al., 2020. Front Immunol 11

 

Keywords

gut microbiota ; foal ; intestinal mucosa ; parasitism ; fibrolysis ; vertical transmission

 

Thesis advisory panel

Thierry Boulinier, CNRS, Centre d’écologie fonctionnelle et évolutive, université de Montpellier
Pierre Lapaquette, Université Bourgogne Europe, UMR PAM, équipe AFIM
Tanguy Hermange, Centre hospitalier vétérinaire équin du Livet