Horse health

Understanding the needs of aged or chronically ill animals and enabling them to have a better quality of life requires a closer look at equine health. In combination with modern, but also alternative treatment methods, physical and physiological health factors are observed in old horses. The quality of life of rescued horses at Gut Aiderbichl can thus be sustainably ensured.

Hindgut flora in old horses

The population of older horses is growing worldwide. However, aging is associated with physical and physiological changes. The development of the microbiota inhabiting the hindgut during this aging process has been little studied until nowadays. Since this microbiota plays an essential role in the digestion of fibers, the support of metabolism and an adapted immunity, it is necessary to maintain a "healthy microbiota".

The aim of the "Healthy Aging" project is to increase knowledge about the senescence of the equine intestinal microbiota and the associated digestive, metabolic and immune functions. The knowledge gained should make it possible to develop recommendations, especially nutritional recommendations, for maintaining the health and well-being of the horse in old age.

Effects of aging on the hindgut flora of horses

Understanding the effects of aging on the fecal microbial ecosystem to promote healthy aging in horses.

Basis/Starting point: The equine large intestine harbors millions of different microorganisms that play an essential role in digestion and energy provision. Under the influence of environmental or intrinsic factors, alterations in the microbiota of the large intestine can occur, which can worsen the health and/or well-being of the horse. One of these factors is aging, although little is known about its effects on the microbiota. Little existing information reports a decrease in bacterial diversity in aged horses, which is indeed consistent with data in humans. Such a decrease may lead to a lower resistance of the microbial ecosystem to environmental stresses. In addition, too little information is known about the evolution of the efficiency of crude fiber digestion in horses with increasing age, which is crucial for energy provision, digestive health and consequently the general health of the animal.

Objective: The objective of this project was to investigate the changes in fecal microbiota that occur with age in horses. This led to: (1) the study of the age-related evolution of the bacterial composition of the fecal microbiota and (2) the evaluation of the effects of these changes on digestion. To answer these questions, 50 horses between 6 and 30 years old were monitored under the same feeding regime, and fecal samples were collected and analyzed.

New findings: Several fecal parameters indicative of bacterial activity were affected by age, with differences between older horses (≥26 years old) and younger horses that were steadily increasing and highly. These results suggest high-grade age-related changes in digestion, possibly caused by composition and/or activity changes in the microbiota. Bacterial structure in the fecal ecosystem - currently under investigation - will provide complementary information to understand the digestive evolution of the equine colon with age.

Outlook: The results on the alteration of the fecal bacterial microbiota with age will help to propose husbandry recommendations for horses adapted to their age, especially feeding adaptations. The observed changes in the fecal microbiota open perspectives for understanding the causative agents of microbiota-mediated diseases in older horses. With further insights, this could lead to promoting healthy aging in horses.


This work was presented at the Equine Science Society Symposium in 2021:

Buttet, M., Omphalius, C., Milojevic, V., Julliand, V., & Julliand, S. (2021). Assessment of the impact of age on fecal microbial ecosystem in horses. Journal of Equine Veterinary Science, 100, 103474.

A peer-reviewed publication is in preparation and is expected to be published by the end of 2022.

Project Management: Lab to Field

Feeding management to promote healthy aging

Age-related alteration of microbiota, digestion and low-grade inflammation in horses - How to promote healthy aging through feeding management?

Basis/Starting point: The population of aging horses has increased worldwide in recent decades. This trend may face a change in important physiological functions and lead to a change in overall health status. The ongoing interaction between gut microbiota and immune system emphasizes the importance of understanding these functions under the influence of aging. It has been previously shown that an immunosenescence phenomenon occurs in aging horses and this immunity reduction is juxtaposed with a chronic, low-grade, systemic, and asymptomatic inflammatory state (termed inflammatory aging or inflammaging). Based on the preliminary study results proving differences in fecal parameters between adult and horses over 26 years of age, the observed microbiota changes could have severe consequences, especially in older horses that develop metabolic disorders more often.

Since diet is one of the most important factors in the functional diversity of the microbiota, and can be easily adapted, it was decided to investigate how feeding management could benefit the gut microbiota in older horses and the associated digestive and immune functions. This motivated the establishment of this project to promote healthy aging in horses.

Objective: The goal of the project is to determine if fibrolytic (crude fiber digestion) capacity and inflammaging develop in accordance with age-related changes in the microbiota. This will include:

  1. Comparison of crude fiber degradation efficiency in old versus adult horses
  2. To investigate the relationships between microbiota composition and activity, crude fiber digestion, and mild inflammation in aged and adult horses
  3. Identify relevant biomarkers that can be readily used to track age-related changes
  4. Compare different feeding regimens for older horses to determine the most appropriate

To achieve these goals, three studies will be conducted in France from 2021 to 2023.

New findings: The results of the first study, conducted in the first half of 2022, are currently being analyzed. These data will be available by the end of 2022.

Outlook: Based on the results on changes in microbiota, fibrolytic and immune function, revised and scientifically based feeding recommendations will be provided to horse owners. This aims to promote the health and well-being of the oldest horses, but also to optimize feeding management to keep horses in the "senior category" healthier.

Publication: This work will be presented through scientific communication tools (international conferences and peer-reviewed publications) and through popularization articles for horse owners.

Project Management: Lab To Field, Institut Agro Dijon - UMR PAM, Prof. DVM, PhD, Veronique Julliand.

Treatment of melanoma in horses

Project name: Treatment of equine skin tumors with betulinic acid using transcutaneous application methods.

Basis/Starting point: Equine malignant melanoma (EMM) is one of the most common skin tumors in horses and it's most common in white horses (gray horses). Up to 80% of gray horses over 15 years old develop malignant melanoma. The tumors are mainly found on the tail rump, perianal area, genitalia, eyelids, lip, parotid gland or air sacs. They show a slow, displacing growth and tend to metastasize to the internal organs in the progressive stage. The complaints of the sick animals are initially of a mechanical nature (problems with defecation or urination, feed intake, eyelid closure, etc.), but as the disease progresses it can severely restrict the quality of life of the horses and also cause far-reaching problems due to metastasis.

There is no standard therapy for the treatment of EMM so far. Currently, the tumors are mostly treated surgically or with chemotherapy. For small tumors, these treatment methods show partial success, but the prognosis for larger tumors is much worse. In addition, the administration of chemotherapeutic agents carries risks for the treated animal, the treating veterinarians as well as the horse owners.

Objectives: The goal of this study is to find a new, local treatment method that is effective but also safe for the treated animal, the treating veterinarians and animal owners. Furthermore, the therapy method should be easy to perform and non-invasive.

Betulinic acid is a naturally occurring secondary plant compound derived from the bark of birch and sycamore trees. Betulinic acid and the derivative NVX-207 inhibit the growth of melanoma cells and have, among other things, anti-inflammatory, antiviral and wound-healing properties.

As both active ingredients have already produced promising results in several studies for the treatment of EMM, these active ingredients are being further investigated. To this end, the concentrations of the active ingredients in new microemulsion gels are being increased in order to better overcome the skin barrier and thus achieve higher concentrations of active ingredients in the skin.

Results/New findings: The substances under investigation are first tested under laboratory conditions. This involves testing whether the active substances applied to the skin reach sufficient concentrations in the skin either dissolved in the microemulsion gel or with the aid of a transdermal oxygen-assisted application method. Initial results show that the desired active ingredient concentrations in the skin could be achieved with all tested substances and both tested application methods.

Outlook: The aim of this study is to successfully treat horses suffering from Equine Malignant Melanoma with these newly developed treatment methods.

Currently, the evaluation is carried out in order to decide which of the tested substances will be applied to the diseased horses. The treatment trial of the diseased horses will be carried out at the equine rehabilitation center in Switzerland. Preparations for this are currently being made.

Project management: Dr. med. vet., DVM-PhD Karina Klein, Prof. Dr. med. vet. Jessika-M. V. Cavalleri

Quality of life of horses

Research Platform aims at an intensive cooperation and exchange between Gut Aiderbichl and the University of Veterinary Medicine Vienna in the field of research on ethically relevant veterinary aspects of the human-horse relationship. In particular, the focus is on decision-making processes and their criteria as well as necessary therapy decisions, in view of old and/or chronically ill animals. The interdisciplinary projects of the research platform approach the complex topic of the horses' quality of life from different perspectives in order to be able to support good decisions for the horses at Gut Aiderbichl and beyond.

Quality of life in old and chronically ill horses

Basis/Starting point: Although quality of life has been used for many years to guide decisions regarding treatment and euthanasia of animal patients, there is currently no universally accepted definition of "quality of life" in horses, no consensus on the factors that contribute to determine the quality parameters and no established methodology for its evaluation.

Objectives: The objective of this project is to develop an examination scheme to evaluate equine quality of life and to make decisions regarding veterinary interventions in geriatric and/or chronically ill horses.

Results/New findings: As part of the study, horses at Gut Aiderbichl are regularly examined over a period of years. During each study period, the horses are equipped with a wearable sensor for 5-10 days. The sensors show how much time the horses spend in various activities, such as eating, resting, lying down or moving around. During the examination period, the horses are also examined by a veterinarian, so deviations in the measurement data can be linked to changes in health.

Outlook: Deviations in the measured data, e.g. in feeding times or lying times, or changes in behavior, change in posture, as well as a visibly painful face can be an indication of (health) problems. The horses undergo a more detailed examination to find the cause of the deviation and to develop tailored interventions, such as postural optimization or medical therapy to improve the well-being of the horse.

Publications: Auer U, Kelemen Z, Engl V, Jenner F. Activity Time Budgets-A Potential Tool to Monitor Equine Welfare? Animals (Basel). 2021 Mar 17;11(3):850. doi: 10.3390/ani11030850.

Kelemen Z, Grimm H, Long M, Auer U, Jenner F. Recumbency as an Equine Welfare Indicator in Geriatric Horses and Horses with Chronic Orthopaedic Disease. Animals (Basel). 2021 Nov 8;11(11):3189. doi: 10.3390/ani11113189.

Kelemen Z, Grimm H, Vogl C, Long M, Cavalleri JMV, Auer U, Jenner F. Equine Activity Time Budgets: The Effect of Housing and Management Conditions on Geriatric Horses and Horses with Chronic Orthopaedic Disease. Animals (Basel). 2021 Jun 23;11(7):1867. doi: 10.3390/ani11071867.

Project management: Hon.Prof. Univ.Prof. Dr. Herwig Grimm, Dipl.ACVS Univ.Prof. Dr Dipl.ECVS Jenner Florien

Ethics of end-of-life decisions for aged and/or chronically ill horses

Basis/Starting point: The simple question "How is my horse doing?" presents significant challenges. How can you put yourself in the horse's shoes and how can you know you are right in your assessment of quality of life? This project addresses quality of life in chronically ill and aged horses in light of increasing opportunities in veterinary medicine and related questions about the appropriateness of end-of-life therapies for horses.

Although quality of life is relevant as an important decision criterion for therapies and for euthanasia, it's a concept without a clear definition and, moreover, complex to evaluate in practice. In addition, there are usually several parties involved with different approaches and relationships to the horse, such as horse owner and veterinarian, who do not always agree on how best to proceed with a horse.

Objectives: Our project therefore addresses the question of what quality of life means in horses and how to apply this concept meaningfully in practice to make responsible decisions for chronically ill and old horses. What difficulties do stakeholders encounter in practice when applying this concept and how do they deal with them? And how can the different perspectives of those involved be brought together profitably in order to achieve good decisions for chronically ill and old horses?

Results/New findings: Against the background of an extensive literature review, seven focus group discussions were conducted and are currently being evaluated. In these discussions, horse owners, equine veterinarians, equine grooms, official veterinarians, and farriers provided their expertise and experiences regarding decisions for chronically ill and aged horses and the role of equine quality of life in this context.

Outlook: With this project, we hope to support the difficult decisions about therapies and euthanasia in chronically ill and old horses in the best possible way on a scientific basis.


Long, M., Jenner, F., Kelemen, K., Cavalleri J.-M., Auer, U., Grimm, H., 2022. 53. Case discussions in a clinical ethics support service for equine medicine: a field report. In Transforming Food Systems, Proceedings of the EurSafe 2022, Edinburgh, Scotland, 7-9 September 2022; Bruce, D., Bruce, A., Eds; Wageningen Academic Publishers: Wageningen, The Netherlands; pp. 344-349. (


Project Management: Hon.-Prof. Univ.-Prof. Dr. Herwig Grimm

Social contacts and access to resources as indicators of equine well-being and quality of life

Basis/Starting point: Social behavior is both a cause and a consequence of equine welfare and quality of life. Since only close companions are tolerated for affiliative interactions within a horse's personal space, whereas agonistic behavior is indicated by an immediate increase in social distance after contact, proximity (and its duration) is a good indicator of social behavioral traits in horses.

Objectives: This project aims to develop a new complementary equine quality of life assessment tool to enable targeted interventions to improve horse management as well as equine quality of life. This assessment will be based on objective and quantifiable indicators of social relationships and interaction patterns, herd dynamics (access to resources such as feed, lying areas) and time budgets for eating, resting, activity, as well as the Discomfort-Score.

New findings: As part of the study, Gut Aiderbichl's horses are regularly fitted with wearable sensors over a period of years:

  1. To determine the spatial proximity between individual horses and the duration of proximity characteristic of agonistic and affiliative behavior;
  2. To measure individual horses' access to common resources (feed, lying areas);
  3. To compare the social behavior and time budgets of horses kept in stalls singly with paddock access in stable groups to horses kept in open stalls to determine the social contact network of horses under different housing conditions;
  4. To compare social behavior, time budgets, and discomfort scores between healthy young, healthy geriatric, and chronically lame horses because the effects of age and chronic lameness on equine social behavior are unknown and this population is at higher risk for poor quality of life;
  5. To analyze the relationship between measurable social behavior, time budgets, and the discomfort score with the proxy assessment of quality of life.

Outlook: In this study, we establish and validate the use of proximity sensors to quantify social behavior in horses and investigate the influence of different housing conditions and health status on the sociality and interaction network of horses. Incorporating social criteria as a key component of quality of life assessment will facilitate targeting interventions to horses showing changes in social behavior. Similarly, in herds with a high number of agonistic social interactions. This can help improve animal management, welfare, and quality of life for horses.

Project management: Priv.Doz. OÄ Dr. Ulrike Auer, Dipl.ACVS Univ.-Prof Dr Dipl.ECVS Jenner Florien

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