New virus found in Swiss horses

© Viacheslav Nemyrivskyi Dreamstime.com

  

Swiss researchers have identified a novel virus in the brains of four horses that were
euthanased after developing neurological disease, prompting investigations into whether the virus may represent an emerging cause of equine central nervous system (CNS) disease.

Since late July 2026, equine referral hospitals at the Universities of Bern and Zurich have seen an increase in horses presenting with neurological signs including ataxia, muscle fasciculations, hypersensitivity and lethargy. Extensive diagnostic investigations failed to identify recognised infectious causes of neurological disease in many of these cases.

Researchers at the Swiss Institute of Virology and Immunology (IVI), working with the Vetsuisse Faculty at the University of Bern, subsequently detected genetic material from a Shamonda-like virus, an Orthobunyavirus in the Simbu serogroup, in brain tissue collected from four affected horses following post-mortem examination. Three cases originated from Zurich and one from Bern. This is the first reported detection of a Simbu serogroup Orthobunyavirus in horses in Europe.

The virus has been confirmed in post-mortem brain tissue from four horses with neurological disease. It has not yet been found in blood or cerebrospinal fluid from affected live horses, so ante-mortem diagnosis is currently not possible. Antibody testing can show previous exposure, but cannot confirm that the virus caused the neurological disease. There is currently no specific treatment, and affected horses receive supportive care.

Like other members of the Simbu serogroup, the virus is believed to be transmitted by Culicoides biting midges. Related viruses, including Schmallenberg virus, are well recognised in European livestock.

At present, there is no evidence that the Shamonda-like virus causes neurological disease in horses. Although its detection in affected brain tissue makes it a plausible candidate, researchers have not established a causal relationship. Further studies are needed to determine whether the virus is responsible for the recent increase in neurological cases in Switzerland or whether its presence is incidental.

Veterinarians investigating horses with neurological signs should therefore continue to consider established differential diagnoses, including equine herpesvirus (EHV), West Nile virus (WNV) and tick-borne encephalitis, while research into the Shamonda-like virus continues.

The UK's Equine Infectious Disease Surveillance (EIDS), based at the University of Cambridge, reports that there is currently no evidence of Shamonda-like virus-associated disease in horses in the UK. However, because infected Culicoides midges may be transported long distances by wind, and horses continue to move between mainland Europe and the UK, the situation is being monitored closely. 

 

For more details, see:

https://www.ivi.admin.ch/en/neues-orthobunyavirus-der-simbu-serogruppe-bei-rindern-entdeckte

Feeding strategies for horses with severe asthma: effects on behaviour and welfare

    

Equine asthma is a chronic respiratory disease that can be triggered or worsened by inhaling
dust, mould, or other airborne particles commonly found in conventional dry hay. Managing the diet is an essential part of treatment, as feed type can influence not only respiratory health but also time budgets and welfare-related behaviours.

Recent research has compared the effects of feeding steamed hay and alfalfa pellets on horses suffering from severe asthma, shedding light on how different low-dust diets affect feeding behaviour, lung health, and overall well-being.

In a controlled study involving nine severely asthmatic horses, Antoine Symoens  and colleagues at the University of Montreal, Canada evaluated the effects of two low-dust feeding regimes - alfalfa pellets and steamed hay - on feeding duration, activity patterns, and gastric health.

The horses were housed indoors and first fed dry hay to induce a clinical flare-up of asthma. They were then placed on either steamed hay or alfalfa pellets for four weeks, using a crossover design so that each horse experienced both diets. Their behaviour was recorded for 18–22 hours at multiple stages during the trial, and gastroscopies were performed before and after each feeding period to assess gastric ulcers.

Results showed clear differences in eating patterns between the two diets. When fed steamed hay, horses spent a consistent proportion of their day eating - about 48% - both during the first and fourth weeks of feeding. In contrast, when horses were switched to pellets, the time they spent eating dropped significantly by roughly one-third in the first week. Interestingly, horses on the pelleted diet appeared to adapt by breaking up their feeding into shorter, more frequent meals, a pattern described as “fragmented eating.” This adjustment might help maintain some degree of natural foraging behaviour despite the rapid consumption time associated with pellets.

From a welfare perspective, steamed hay appears to preserve a more natural feeding time budget. Horses in the wild spend most of their day grazing, and maintaining this prolonged eating activity is associated with better digestive health and lower risk of behavioural issues such as boredom or stereotypies. Short feeding times, as seen with pelleted diets, can disrupt this pattern, potentially leading to frustration or undesirable behaviours.

However, feeding choices must also consider respiratory benefits. Earlier findings have shown that while steamed hay is much less dusty than untreated hay, it may be less effective than alfalfa pellets at improving lung function in asthmatic horses. Therefore, while steamed hay supports more natural feeding behaviour, pellets may provide a stronger advantage for respiratory management. Importantly, the study found that neither diet had an influence on the occurrence of squamous gastric ulcers, an encouraging finding for owners concerned about ulcer risk.

In practical terms, managing an asthmatic horse’s diet involves balancing multiple factors. Replacing dusty or mouldy hay with low-dust alternatives, such as haylage, steamed hay, or suitably formulated pellets, can help reduce respiratory irritation. For overweight or laminitis-prone horses, haylage may not be ideal due to its higher energy content, making steamed hay a more moderate choice. Combining different low-dust feeds could offer the best compromise, supporting both lung health and natural feeding behaviour.

In conclusion, when feeding horses with severe asthma, steamed hay helps maintain normal feeding time and behaviour, contributing positively to welfare, whereas pelleted diets offer greater respiratory benefits but may shorten eating duration. Selecting or combining these diets thoughtfully allows owners to meet both the physiological and behavioural needs of asthmatic horses.

 

For more details, see:

Antoine Symoens, Mathilde Leclère, Valentine André, Marion Desmarchelier,

Behavioral effects of two diets used for the management of severe equine asthma,

Journal of Veterinary Behavior, (2026) Vol 84, pp34-40,

https://doi.org/10.1016/j.jveb.2025.12.007

Could dietary supplementation with polyphenols help horses with equine asthma?

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 Equine Asthma Syndrome (EAS) is a chronic, non-infectious respiratory disease of adult horses, characterised by airway inflammation, mucus accumulation, and variable airflow obstruction. Clinical signs range from coughing and nasal discharge to exercise intolerance and increased respiratory effort, particularly when horses are stabled or exposed to dusty environments. EAS is now recognised as a major cause of poor performance and reduced welfare in affected horses, with similarities to human asthma in both pathology and clinical presentation.

One area of interest in human medicine has been the potential anti-inflammatory effects of dietary polyphenols. Polyphenols are naturally occurring compounds found in plants, particularly in fruits, vegetables, tea, and herbs. They act as antioxidants and modulators of inflammatory pathways. In human asthma, certain polyphenols have been reported to reduce airway inflammation and improve lung function. Despite this promising background, their application in equine asthma had not been previously explored.

 

Researchers from the Department of Large Animal Medicine at the University of Georgia set out to investigate whether dietary polyphenol supplementation might offer similar benefits in horses with EAS. Their study aimed to evaluate the effects of a mixed polyphenol supplement on both systemic and pulmonary inflammation, as well as on bronchoalveolar lavage (BAL) cytology and clinical respiratory signs in healthy and asthmatic horses. The team hypothesised that polyphenol supplementation would decrease inflammation in both groups, and in asthmatic horses, would also lead to improvements in BAL cytology and respiratory signs.

 

The research was conducted in two parts.

 

Part One:
Eighteen horses were enrolled, including eight healthy horses and ten with asthma. Each horse received the polyphenol supplement daily for 6–8 weeks. Before and after supplementation, the researchers performed a thorough physical examination, collected BAL fluid, and measured cytokine concentrations in both serum and BAL fluid.

 

Findings: Horses with mild-to-moderate asthma showed improved BAL cytology after supplementation. In particular, the percentage of neutrophils (a marker of airway inflammation) decreased significantly in the asthmatic group. Levels of pro-inflammatory cytokines, including interleukin-6 (IL-6), also decreased after supplementation. Interestingly, interleukin-10 (IL-10), typically considered an anti-inflammatory cytokine, also showed a greater reduction in asthmatic horses compared with healthy ones, though the functional significance of this is not yet clear.

 

Part Two:
Ten asthmatic horses were divided into two groups: five received the polyphenol supplement, and five served as unsupplemented controls. All horses were maintained on a low-dust diet for four weeks, after which airway inflammation was deliberately exacerbated by feeding dusty hay for another four weeks. Throughout, the team assessed clinical signs, rebreathing examination findings, and pulmonary inflammation.

 

Findings: Supplemented horses demonstrated clear clinical benefits. They had significantly lower respiratory rates than controls during the dusty hay challenge, and fewer supplemented horses showed abnormal findings on rebreathing examinations. These improvements occurred despite evidence of ongoing airway inflammation, suggesting that supplementation may have helped to blunt the clinical impact of the environmental challenge.

 

The polyphenol supplement was well tolerated and readily eaten by horses when fed as a top-dressing, making it a feasible option in practice. Importantly, supplementation was not presented as a replacement for environmental management but rather as an adjunct. Controlling dust exposure, optimising ventilation, and feeding low-dust forages remain the cornerstone of asthma management in horses. However, dietary polyphenols may provide additional support by modulating inflammatory processes at both systemic and pulmonary levels.

 

This research provides preliminary evidence that dietary polyphenol supplementation can reduce airway inflammation markers and improve clinical signs in horses with mild-to-moderate equine asthma. While further work is needed to establish long-term effects, optimal dosing, and the mechanisms involved, polyphenols represent a promising area of nutritional support for respiratory health in horses. 

 

 

For more details, see:

 

K.M. Andrews, L.J. Berghaus, K.A. Hart,

Effects of mixed polyphenol supplementation on lower airway inflammation in horses with Equine Asthma Syndrome,

Journal of Equine Veterinary Science,(2025) Vol 154,105681,

https://doi.org/10.1016/j.jevs.2025.105681

Horses Inside Out Conference 2026

 Gillian Higgins has announced the 2026 Horses Inside Out Conference, with early bird tickets now available.

The conference will focus on Soundness and Symmetry in the Horse - the balance and harmony of the musculoskeletal system and its impact on movement. Across the programme, speakers will explore what soundness and symmetry mean in practice, how training and management can support them, and the challenges that may arise along the way.

Designed for professionals and equestrians from all disciplines, the event offers a rare opportunity to hear from world-leading experts, share the latest research, and consider practical applications to improve the health, welfare, training, and performance of horses.

The 2026 conference will differ from previous years with a three-day structure: two days of presentations followed by a practical day. The first two days, held at Holywell Park Conference Centre, Loughborough University (UK), will feature lectures from leading equine professionals on anatomy, biomechanics, training, and therapy. The third day, will focus on Soundness and Symmetry in Practice, with live demonstrations and practical sessions led by guest experts.

For more details, see: 

https://www.hioconference.com

Does obesity influence inflammatory responses in horses with equine asthma?

(c) Abby Khoriaty Dreamstime.com

 Equine asthma is a chronic respiratory condition that affects many horses, particularly those kept in stabled
environments or exposed to dust and allergens. It is characterised by airway inflammation (primarily driven by neutrophils)  leading to symptoms such as coughing, nasal discharge, and laboured breathing. Inflammatory flare-ups can significantly impair lung function and reduce performance.

 At the same time, equine obesity is becoming increasingly prevalent among domestic horses, largely due to overfeeding, limited exercise, and modern management practices. Obesity is already known to affect metabolic health and immune function in other species, including humans. This raises an important question: Could excess body fat make equine asthma worse by altering how the immune system responds to inflammation?

 A research team led by Alejandro Albornoz at the Universidad Austral de Chile set out to investigate whether obesity influences the inflammatory profile of horses with equine asthma. Their study, published in the open-access journal Animals, focused specifically on neutrophils - the white blood cells central to the airway inflammation seen in asthmatic horses.

 The researchers compared two groups of asthmatic horses that were in clinical remission (i.e. not experiencing active symptoms). The horses were divided into obese and non-obese groups, based on their body condition scores (BCS). Blood samples were taken to assess systemic inflammatory markers and to analyse how the horses’ neutrophils responded to immune challenges in the lab.

The results showed clear differences between the two groups:

• ·       Obese horses had significantly higher blood levels of interleukin-1β (IL-1β), a potent inflammatory cytokine involved in many immune responses.
• ·       They also had increased peripheral neutrophil counts, indicating a more active systemic inflammatory state.

When stimulated in the lab, neutrophils from obese horses:

• ·       Produced more reactive oxygen species, a marker of a strong oxidative response.
• ·       Showed greater expression of IL-1β genes after exposure to inflammatory triggers (such as lipopolysaccharide).

These responses point to a hyperinflammatory neutrophil phenotype - meaning these immune cells were more reactive and potentially more damaging to lung tissue if activated in the horse’s airways.

To better understand these changes, the team also conducted metabolomic profiling of the neutrophils - essentially examining the small molecules and biochemical pathways active within the cells.

They identified 139 different metabolites, and found key differences in:

• ·       Fatty acid biosynthesis
• ·       Branched-chain amino acid metabolism
• ·       Glutathione-related antioxidant pathways
• ·       Tricarboxylic acid (TCA) cycle intermediates

In particular, levels of itaconate, citraconic acid, and citrate were significantly elevated in the obese group. These molecules are known to regulate immune cell activity, and their presence suggests a state of metabolic reprogramming that primes neutrophils for a heightened inflammatory response.

The researchers conclude that obesity alters neutrophil metabolism and function in horses with asthma, making these immune cells more reactive to inflammatory stimuli. This may contribute to more persistent or severe airway inflammation, potentially making the disease harder to control. 

The findings highlight the importance of addressing obesity as part of asthma management. Controlling body condition may reduce systemic inflammation and help prevent disease flare-ups. The study also opens the door to future therapies that target neutrophil metabolism as a way to modulate inflammation in chronic equine diseases.

For more details, see:

Albornoz, Alejandro, Beatriz Morales, Valentina Bernal Fernandez, Claudio Henriquez, John Quiroga, Pablo Alarcón, Gabriel Moran, and Rafael A. Burgos. 

Obesity-associated metabolomic and functional reprogramming in neutrophils from horses with asthma

Animals (2025) 15, no. 13: 1992. 

https://doi.org/10.3390/ani15131992

New device aims to help asthmatic horses breathe more easily

The new equine respirator (Tim Brouk)

A novel collaboration between Purdue University’s College of Health and Human Sciences and the College of Veterinary Medicine may offer significant relief for horses suffering from asthma—a common respiratory condition often triggered by inhaled particles such as mould spores found in dusty hay.

Equine asthma, like its human counterpart, is frequently linked to allergic sensitisation to airborne irritants. While a range of treatment and management options exist, the most effective strategy remains straightforward: minimise exposure to the particles that trigger the condition. This is typically attempted by soaking or steam-treating hay to reduce airborne dust. However, researchers at Purdue have taken this one step further by developing a wearable device that could filter out harmful particles before they even reach the horse’s airways.

At the heart of this innovation is an equine respirator—a specially designed breathing mask that attaches directly to a horse’s bridle or head collar. The device allows the horse to breathe filtered air through an intake positioned over the bridge of the nose, while exhalation occurs through valves located near the nostrils. Crucially, the design allows horses to eat and drink while wearing the respirator, making it suitable for continuous use in dusty environments like stables or arenas.

The project was born out of a cross-disciplinary partnership. Dr. Jae Hong Park, associate professor of Health Sciences, had been working on developing human respirators, especially for welders working in manufacturing facilities. His research caught the attention of Dr. Laurent Couëtil, a professor of Large Animal Internal Medicine in the College of Veterinary Medicine, who wondered if a similar approach could be adapted for equine use.

Momentum built when Chang Geun Lee, a Ph.D. candidate in Health Sciences with a background in mechanical engineering and industrial design, joined Park’s lab. Lee brought a unique combination of technical skills and practical design experience that proved instrumental in creating a functional and comfortable respirator for horses.

The team, which also includes Laura Murray, RVT and research technologist in the Department of Veterinary Clinical Sciences, spent months designing, prototyping, and refining the respirator. Their efforts have culminated in a practical tool that could significantly improve the quality of life for horses affected by respiratory issues—particularly those regularly exposed to dusty environments.

By combining expertise in health sciences, veterinary medicine, and engineering, this collaboration exemplifies the power of interdisciplinary research to solve real-world problems—and could mark a significant advance in the management of equine asthma.

The research team are now looking to see if the device could be made available for general use.

For more details, see: 

https://vet.purdue.edu/news/asthmatic-horses-can-breathe-easier-thanks-to-purdue-health-and-human-sciences-and-college-of-veterinary-medicine.php

Discovery links genes to performance-limiting disease in Thoroughbred racehorses

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 New research has identified specific genetic markers linked to Recurrent Laryngeal Neuropathy (RLN), a disease that significantly impacts the performance of Thoroughbred racehorses. This discovery, hailed as a major step forward in combating this debilitating condition, paves the way for the development of a genetic test to identify horses with a threefold increased risk of developing RLN. 

Often referred to as laryngeal hemiplegia or "roaring," RLN is an upper respiratory tract (URT) disorder that affects up to 18% of Thoroughbred horses. The condition is characterised by the progressive degeneration of the recurrent laryngeal nerve, which controls the muscles that open the horse’s airway. As the disease progresses, airflow during exercise becomes restricted, leading to laboured breathing, reduced oxygen intake, and impaired athletic performance.

 

RLN represents a significant challenge for the Thoroughbred racing industry due to its economic and competitive implications. While pre-purchase examinations, including upper respiratory endoscopy ("scoping"), can detect RLN, resting evaluations in young horses often fail to identify the disease or predict its future onset.

 

To tackle these challenges, researchers at University College Dublin, in collaboration with Equinome and a world-class Thoroughbred training facility, conducted an extensive study funded by Research Ireland. The research team employed state-of-the-art diagnostic methods, including resting and overground exercising endoscopy of the upper airway, as well as laryngeal ultrasonography. This rigorous approach ensured accurate phenotyping of horses as either RLN cases or controls.

 

The study analysed over 200 Thoroughbred horses in training, utilizing both clinical evaluations and genetic testing. The case-cohort group was supplemented with detailed questionnaires to capture additional phenotypic data. A full report of the research is published in the Equine Veterinary Journal.

 

Using advanced DNA technologies, researchers conducted a genome-wide association study (GWAS) to identify genetic variants associated with RLN. They genotyped 43,831 single-nucleotide polymorphisms (SNPs) from 235 horses (110 RLN cases and 125 controls) and estimated the heritability of the trait. The findings revealed a set of genetic markers that significantly contribute to RLN risk, independent of other factors such as height.

 

This discovery is particularly important because it confirms a genetic predisposition to RLN and identifies specific markers that could be used to predict the disease in Thoroughbreds.

This research marks a significant advance in equine genetics and respiratory health, offering new hope for addressing RLN, a disease that has long plagued the Thoroughbred racing industry. The ability to identify horses with a higher genetic risk for RLN has far-reaching implications for the Thoroughbred racing industry. 

 

The next step will involve translating these findings into a practical genetic test that can be readily adopted by breeders, trainers, and veterinarians.

 

UCD Professor in Equine Genomics and Chief Science Officer at Equinome, Emmeline Hill said the new findings would “lay the groundwork for the development of a genetic test to improve the welfare of horses that have a genetic predisposition to the disease. 

“As well as identifying horses with an increased risk of disease, this new information could also inform breeding guidance to reduce the incidence of the disease and provide targets for new therapies.”

Project lead Lisa Katz, UCD Professor in Equine Internal Medicine, added: “Understanding the genetic risk of your horse for roaring can help with early intervention and management. This might include monitoring highly predisposed horses more closely and considering surgical interventions at an earlier stage to improve treatment success.”

 

For more details, see: 

 

A genome-wide association study for recurrent laryngeal neuropathy in the Thoroughbred horse identifies a candidate gene that regulates myelin structure

Charlotte L. McGivney, Beatrice A. McGivney, Gabriella Farries, Katie F. Gough, Haige Han, Amy R. Holtby, David E. MacHugh, Lisa Michelle Katz, Emmeline W. Hill

Equine Vet J (2025)

https://doi.org/10.1111/evj.14461

Air sampling for flu detection

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 Air sampling may provide a safe and effective method for detecting horses infected with equine influenza virus (EIV), according to new research from Japan.

EIV, a highly contagious respiratory disease in horses, spreads through aerosolised droplets, direct contact, and contaminated surfaces (“fomites”). Traditionally, confirming EIV infection requires nasopharyngeal swabs, which can be invasive and challenging, especially for untrained or aggressive horses.

 

A study conducted by researchers at the Equine Research Institute, Japan Racing Association, in Shimotsuke, Tochigi, Japan, has demonstrated that EIV can be recovered directly from the air surrounding infected horses. The research, led by Manabu Nemoto and colleagues and published in Veterinary Microbiology, involved experiments with two horses intentionally infected with EIV and housed in individual stalls.

 

Air samples were collected daily for 13 days post-inoculation using an air sampler. The findings showed that EIV RNA was detected in 26 out of 28 air samples using real-time RT-PCR and in 23 samples using a rapid molecular test kit. Significantly, viral RNA was detected in the air before the horses displayed clinical symptoms, emphasising the potential of air sampling for early detection.

 

The research team highlighted that air sampling is a non-invasive and safe alternative to traditional methods, avoiding the risks associated with swab collection. Additionally, the combination of air sampling with rapid molecular diagnostic kits, which can identify viral RNA in under 30 minutes, offers a practical and efficient approach for monitoring and controlling EIV outbreaks.

 

They suggest that this method could be particularly beneficial in quarantine facilities and other high-risk settings where early detection and containment of EIV are essential.

 

For more details, see:

 

Manabu Nemoto, Nanako Kawanishi, Yoshinori Kambayashi, Hiroshi Bannai, Takashi Yamanaka, Koji Tsujimura,

Detection of equine influenza virus gene in the air around infected horses,

Veterinary Microbiology, (2025), Vol 302, 110388,

 

https://doi.org/10.1016/j.vetmic.2025.110388

Horses in Asia Found Infected with H5N1 Avian Influenza

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A recent study has revealed that horses in Asia have been infected with H5N1 avian influenza,
with these infections occurring undetected.  

The research, led by Professor Pablo Murcia from the MRC-University of Glasgow Centre for Virus Research, in collaboration with an international team of scientists from the US and Mongolia, involved antibody testing on horse herds in Mongolia.  The findings, published in Emerging Infectious Diseases, reveal asymptomatic infections in Mongolian horse herds.

 

The researchers tested horse herds in two distinct Mongolian regions: a wetland area with a high population of wild birds and a dry area with low bird density. The results showed higher exposure rates in the wetland region. Importantly, there were no reports of previous respiratory disease outbreaks among the horses, suggesting that the infections were acquired asymptomatically.

 

These findings confirm that avian influenza can spread to other species, including horses. While equine influenza is typically caused by the H3N8 subtype, the detection of H5N1 highlights the potential for avian influenza to infect horses.

The study raises concerns about cross-species transmission, particularly in agricultural environments where horses may be exposed to infected livestock. Since March 2023, the rapid spread of H5N1 in US dairy cattle has amplified the risk of horses contracting avian influenza.

Coinfection with H5N1 and equine influenza (H3N8) could result in genetic reassortment, potentially creating new influenza strains with unpredictable consequences for animals and humans. Professor Murcia noted parallels to the 2009 swine-origin influenza pandemic, emphasizing the importance of preventing such reassortment events.

The researchers conclude by recommending serologic surveys in premises that keep horses. Such studies, they say, would aid early virus detection, provide a comprehensive picture of the changing ecology of avian influenza viruses, and inform the design of control measures to prevent influenza emergence.

This study highlights the need for:

1. Enhanced surveillance of influenza infections in horses, particularly in regions with high wild bird densities or significant interaction with infected livestock.
2. Strengthened biosecurity measures to reduce interspecies transmission in agricultural settings.
3. Further research into the mechanisms of avian influenza spillover and the potential for new virus emergence.

For more details, see: 

 

Batchuluun Damdinjav, Savitha Raveendran, Laura Mojsiejczuk, Ulaankhuu Ankhanbaatar, Jiayun Yang, Jean-Remy Sadeyen, Munir Iqbal, Daniel R. Perez, Daniela S. Rajao, Andrew Park, Mafalda Viana, and Pablo R. Murcia (2025)

Evidence of Influenza A(H5N1) Spillover Infections in Horses, Mongolia.

Emerging Infectious Diseases, 31(1) 

https://doi.org/10.3201/eid3101.241266 

https://www.gla.ac.uk/news/headline_1134067_en.html

Bacterial gut diversity in TB foals improves future racing performance

 The composition of gut bacteria in one-month-old Thoroughbred foals can predict their future
athletic performance, according to a new study from the University of Surrey. Foals with lower bacterial diversity at 28 days old were also found to have a significantly increased risk of respiratory disease later in life.

 Researchers from Surrey's School of Veterinary Medicine and School of Bioscience, led by Professor Chris Proudman, examined the gut bacterial composition of Thoroughbred foals bred for flat racing and its impact on their long-term health and performance.

The three-year cohort study explored the interactions between early-life gut bacterial communities, health outcomes in later life, and athletic performance on the racetrack. The findings were published in Scientific Reports.

 

The study involved analysing 438 faecal samples from 52 foals, tracking their respiratory, gastrointestinal, orthopaedic, and soft-tissue health from birth to three years of age. The researchers also analysed data on race performance, including finishing positions, official ratings, and prize money earnings as measures of athletic performance.

 

Professor Chris Proudman, Professor of Veterinary Clinical Science at the School of Veterinary Medicine at the University of Surrey, said:   "Minimising the risk of disease and injury is important for the welfare of racehorses, and maximising their athletic potential is important for their owners. We have found that gut health, in particular the health of gut bacterial communities very early in life, exerts a profound and enduring impact on racehorse health and performance."

 

The study found a positive association between athletic performance and higher faecal bacterial diversity at one month old. Specifically, a higher abundance of the bacteria Anaeroplasmataceae was linked to a higher official rating, and increased levels of Bacillaceae at 28 days old were associated with better race placings.

 

The researchers concluded that the gut bacterial composition in the first months of life influences the risk of specific diseases and athletic performance up to three years old. Foals with lower bacterial diversity at one month old had a significantly higher risk of developing respiratory disease, which was also associated with a higher relative abundance of the bacteria Pseudomonadaceae.

 

Interestingly, the study revealed that foals treated with antibiotics during their first month of life had significantly lower bacterial diversity at 28 days old compared to those not treated with antibiotics. These foals also earned significantly less prize money and had a higher rate of respiratory disease later in life.

 

Professor Roberto La Ragione, co-investigator from the School of Bioscience at the University of Surrey, commented, "While antibiotics are essential for treating infections and ensuring the long-term health of foals, their use must be carefully managed. Our study demonstrates that antibiotic treatment can disrupt the gut microbiome with long-term consequences for health and performance. The next phase of our research will focus on minimizing this disruption when antibiotics are necessary."

 

Additionally, the researchers found that low gut bacterial diversity in early life is associated with an increased risk of soft-tissue and orthopaedic issues later on. They believe these health impacts are likely related to immunological priming, though the underlying reasons for the observed negative effects on racehorse performance are still not fully understood.

 

Dr. Kirsten Rausing, Chairman of the International Thoroughbred Breeders Federation and study sponsor through her ALBORADA Trust, remarked, "This ground-breaking study has identified the importance of gut health in our very young foals. As breeders, if we can get this right, we will produce foals that will be healthier, and that will grow into more successful racehorses."  

 

Ongoing research aims to develop novel probiotics to enhance foal gut health in early life and to investigate how antibiotics can be used while preserving gut health.

 

The researchers conclude: “For the first time, this study demonstrates a relationship between early-life gut bacterial communities and subsequent athletic performance that has implications for athletes of all species including humans.”

 

 

For more details, see:

 

Early-life gut bacterial community structure predicts disease risk and athletic performance in horses bred for racing

J. Leng, C. Moller-Levet, R. I. Mansergh, R. O’Flaherty, R. Cooke, P. Sells, C. Pinkham,O.  Pynn, C. Smith, Z. Wise, R. Ellis, A. Couto Alves, R. La Ragione and C. Proudman 

Scientific Reports (2024) vol 14, Article number: 17124 

https://doi.org/10.1038/s41598-024-64657-6 

New research projects receive funding

 Morris Animal Foundation has provided funding for seven new research projects focused on
equine health. These studies aim to address various equine health issues, including contagious upper respiratory disease, and sepsis in foals. 

The research initiatives receiving support are as follows:

 

• Impact of cyproheptadine on blood variables and clinical signs of Pituitary Pars Intermedia Dysfunction (PPID) in Horses. (Dr. Nicholas Frank, Mississippi State University) 

• Development of an effective intramuscular vaccine against strangles, based on the "S" protein of Streptococcus equi subspecies equi (SEE). (Dr. Noah Cohen, Texas A&M University.)

• A novel diagnostic test for Equine Pituitary Pars Intermedia Dysfunction (PPID).( Dr. Dianne McFarlane, University of Florida )

• Increasing understanding of foal sepsis and potential new treatment options (Dr. Katarzyna Dembek, North Carolina State University)

• Examination of a faecal-based test to aid in the diagnosis of gastric ulcers in horses (Dr. Canaan M. Whitfield-Cargile, University of Georgia)

• A study of remote behavioural and physiologic monitoring to assess changes in equine discomfort behaviours and their association with epidural morphine administration. (Dr. Hope Douglas, University of Pennsylvania)

• Investigation into drugs targeting the non-structural protein 4 of African Horse Sickness (Dr. Constantinos Kurt Wibmer, University of the Witwatersrand, South Africa )

 

Dr. Kathy Tietje, Chief Program Officer at Morris Animal Foundation, expressed excitement about supporting these projects, which aim to advance equine health and welfare through innovative research. The studies are scheduled to commence in the current year, contributing valuable insights to improve equid health and well-being.

For more about Morris Animal Foundation, see:

 morrisanimalfoundation.org

Possible new approach to DDSP treatment

 Intermittent dorsal displacement of the soft palate (iDDSP) is a cause of exercise intolerance
and poor performance, particularly in horses involved in strenuous activities such as racing. 

In DDSP, the soft palate, which should fit snuggly around the larynx, flips out of position and obstructs the airway, limiting the horse’s ability to breathe.

 

Various techniques have been used to treat the condition; ranging from the conservative (such as tongue straps, crossed nose bands, glycerine on back of the tongue, treatment of other respiratory problems), to surgery.

 

Laryngeal tie forward (LTF) is a commonly used surgical treatment for the condition with reported success rates up to 80%.  Prosthetic sutures are placed between the thyroid cartilage and the basihyoid bone, to tie the larynx forward and fix it in place to prevent the soft palate dislocating and blocking the airway during exercise.

 

The operation is typically carried out under general anaesthetic, which involves some risk and expense. It has been suggested also that recovery from general anaesthetic may contribute to failure of the prosthesis (sutures). 

 

Clinicians at the University of Queensland School of Veterinary Science have described a series of cases in which they carried out the operation in sedated standing horses.

 

Natasha E. Lean and colleagues reported the work in a recent issue of Veterinary Surgery.

 

They performed Standing LTF in five experimental (normal) horses and five clinical cases with iDDSP. The procedure was carried out under endoscopic guidance, with the horses sedated and the surgical site desensitised with local anaesthetic. No major complications were encountered.

 

The response to surgery was assessed using radiography, and endoscopy. 

The authors conclude that standing LTF is “feasible, mitigates the risk of general anesthesia related complications and reduces cost.”

 

 

For more details, see:

 

Laryngeal tie-forward in standing sedated horses

Natasha E Lean, Albert Sole-Guitart, Benjamin J Ahern 

Vet Surg (2023) Feb;52(2):229-237.

 doi: 10.1111/vsu.13920 

Steaming hay can lead to protein deficiency

 Hay can be treated with steam to reduce the horse’s exposure to inhaled allergens that cause
respiratory disease. Steaming kills potentially harmful microorganisms and binds fungal spores and dust particles to the hay making them less likely to be inhaled 

However, new research shows that steam treatment can have an adverse effect on the digestibility of protein in the hay. 

 

A team of scientists from Martin Luther University Halle-Wittenberg (MLU) has discovered that steam treatment causes a chemical reaction that damages the proteins in the hay and makes them harder for horses to digest. This can lead to signs of nutrient deficiency in the animals and, for example, impair growth or muscle development. A report of the work is published in the journal Animals.

 

Professor Annette Zeyner from the Institute of Agricultural and Nutritional Sciences at MLU explains: “Many horses suffer from lung problems such as equine asthma. The steaming process virtually eliminates all of the living microorganisms and particles in the hay that could be inhaled during feeding and damage the lungs. In theory, the end result is a very good forage," 

 

However, her team discovered that the treatment also has its disadvantages as the steam damages the proteins in the hay. 

 

"A high proportion of the proteins, and the crucial amino acids contained in them, can no longer be digested by the small intestine - in other words the horse lacks these proteins as a result of the steam treatment. However, some of these protein components are essential for horses and they cannot be absorbed in the large intestine," Zeyner continues. 

 

The researchers demonstrated this by examining various hay samples collected from central Germany. In the steamed hay, they found an increased number of products that are generated by the Maillard reaction, an indication that the proteins in the hay have been damaged. This is a reaction that also takes place when food is cooked, baked or fried and is responsible for browning or the development of flavours. 

 

"Proteins are composed of amino acids. The steaming damages them and they form new complexes with sugars in the hay," explains the first author of the study, Caroline Pisch, from MLU. This makes them difficult for horses to digest. According to the researchers’ analyses, the treatment reduced the amount of protein that can be absorbed by the small intestine by almost half. The pre-caecal digestibility of the essential amino acid lysine was over 50% lower after steam treatment.

 

According to Zeyner, this can lead to an undersupply of essential amino acids from the feed, which can be a problem for growing horses or lactating mares; young horses need proteins to grow, and mares need them to produce milk. To make matters worse, protein deficiency causes very unspecific symptoms in the affected animals. These include impaired muscle development and a dull or shaggy coat with so-called "hunger hair" - long isolated hairs in the horse’s coat. 

 

She suggests that horse owners can counteract this risk by enriching the animals’ diet with protein-rich single feedstuffs such as yeast and soybean meal or high-quality protein-rich compound feeds. 

 

The report concludes: “steamed hay is still a proper and sometimes the only possible roughage for horses suffering from respiratory diseases such as equine asthma. Essentially, horse diets based on steamed hay should be balanced accordingly."

 

For more details, see:

 

Effect of Hay Steaming on the Estimated Precaecal Digestibility of Crude Protein and Selected Amino Acids in Horses

Caroline Pisch, Monika Wensch-Dorendorf, Uwe Schwarzenbolz, Thomas Henle, Jörg Michael Greef, and Annette Zeyner. 

Animals(2022) 12, no. 22: 3092. 

https://doi.org/10.3390/ani12223092