Study shows “Bute” can temporarily disrupt assisted breeding in horses

(c) Zuzana Tillerová Dreamstime.com

 Research from Texas A&M University has found that phenylbutazone (“bute”), one of the most
commonly used pain-relief medications in horses, can interfere with artificial breeding techniques, especially at the crucial stages of egg maturation, fertilisation, and early embryo development.

This finding is particularly important for mares involved in assisted reproductive technologies (ART), such as intracytoplasmic sperm injection (ICSI) or embryo transfer. Many donor mares, especially older mares retired from competition or horses working through chronic lameness, may be receiving long-term bute to manage pain. 

Phenylbutazone is a non-steroidal anti-inflammatory drug (NSAID) widely used to manage lameness. While highly effective for pain, the Texas A&M team discovered that it can temporarily reduce the ability of a mare’s egg cells (oocytes) to develop properly in laboratory conditions.

In horses, assisted reproduction is more difficult than in humans. Mature oocytes must be collected, cultured for around 30 hours, and then fertilised by injecting an individual sperm directly into the egg, a process known as ICSI. If the egg fails to mature or the early embryo fails to grow, it cannot be used.

The research team tested the effect of a 10-day course of oral bute on oocyte quality. Oocytes were collected using transvaginal ultrasound-guided aspiration and evaluated shortly after treatment, then again one month and two-and-a-half months later. Cumulus–oocyte complexes (COCs), the small clusters of egg cells and surrounding support cells, were matured in vitro and fertilised using ICSI.

Key findings included:

Immediately after treatment (3 days post-bute):

• Oocytes from treated mares were less likely to be recovered and mature normally.
• Cleavage (early embryo division) rates were significantly lower.
• No fertilised oocytes from bute-treated mares developed into blastocysts, whereas 28% of those from untreated mares did.

Later in recovery (33 and 77 days post-treatment):

• Differences between groups disappeared.
• Oocytes collected after these intervals matured and developed at normal rates.

This means that bute’s negative effect on reproduction is real but temporary. A waiting period of at least one month after stopping bute appears to allow oocyte quality to return to normal.

This study suggests that:

• Egg collections performed shortly after a course of bute may fail, wasting both time and significant financial investment.
• Planning ART procedures around medication withdrawal could improve success rates.
• A minimum 30-day washout period may be advisable before oocyte aspiration.

Future research will explore whether other NSAIDs offer safer alternatives that do not interfere with reproduction.

For more details, see:

Luisa Ramírez-Agámez, Camilo Hernández-Avilés, Canaan M. Whitfield-Cargile, Michelle C. Coleman, Charles C. Love,

Treatment of mares with the non-steroidal anti-inflammatory drug (NSAID) phenylbutazone transiently affects in vitro maturation of equine oocytes and blastocyst development after Intracytoplasmic Sperm Injection (ICSI),

Theriogenology (2024), Vol 223, Pp 53-58

https://doi.org/10.1016/j.theriogenology.2024.04.017

Study finds social contact improves welfare and behaviour in stabled horses

(c) Abby Koriaty Dreamstime

New research has found that even limited social interaction can improve the welfare and
emotional state of horses kept in individual stables. The study showed that horses allowed to spend short periods of time with another horse displayed fewer stress-related behaviours, were calmer around humans, and appeared to perceive their environment more positively.

The research, carried out in France, involved 20 adult saddle-bred sport horses living in individual stalls. Over four months, half of the horses were given one hour of daily social contact in a “meeting box,” where they could interact freely with another horse. The remaining horses stayed fully isolated. Researchers observed all horses in their stalls, during grooming sessions with humans, and in a judgement bias test designed to assess emotional state.

In their stables, horses that had daily social contact displayed fewer stereotypic behaviours such as repetitive movements or abnormal oral actions compared with isolated horses. They also showed lower levels of aggressiveness, apathy, and hypervigilance, all indicators of compromised welfare.

During grooming, the socially housed horses were less tense and more relaxed, showing fewer negative reactions toward handlers. They also spent less time on alert, suggesting that regular interaction with other horses not only improved their general mood but also strengthened their trust in humans.

The results of the judgement bias test supported these behavioural observations. Horses that had daily social contact displayed a more optimistic bias, meaning they interpreted ambiguous stimuli more positively than their isolated counterparts. In welfare science, such optimism is considered a sign of a positive emotional state.

The findings highlight how social needs remain fundamental to equine welfare, even for horses managed in modern livery or competition environments. Horses are inherently social animals, and complete isolation can lead to behavioural problems, reduced welfare, and a less positive relationship with humans.

Overall, the findings indicate that even temporary but regular opportunities for social interaction can enhance the emotional wellbeing of individually housed horses. 

The researchers concluded that providing horses with the chance to engage in natural social behaviours helps reduce stress, prevent the development of stereotypies, and promote a more positive perception of their environment.

These results underline the importance of social needs in horse management. For a highly social species such as Equus caballus, complete isolation can have significant welfare costs. Allowing horses to interact, even for short periods, appears to improve their mental state, behaviour, and responses to human handling - key elements in maintaining both welfare and performance.

This suggests practical applications for yards and training centres where full group turnout may not always be possible.

By meeting horses’ natural social needs, owners and managers can help reduce stress-related behaviours, improve handling responses, and support a more positive emotional outlook.

In summary, horses that are given opportunities for daily social contact appear not only calmer and more optimistic but also more comfortable in their interactions with humans. The study adds to growing evidence that social enrichment, even in small doses, plays a crucial role in promoting both welfare and performance in stabled horses.

 

For more details, see:

 

A. Flamand, L. Robinet, A. Raskin, M. Braconnier, A. Bouhamidi, G. Derolez, C. Lochin, C. Helleu, O. Petit,

The social dimension of equine welfare: social contact positively affects the emotional state of stalled horses,

Animal Behaviour,  (2025) Vol 221,123055.

https://doi.org/10.1016/j.anbehav.2024.123055

UConn study links poor coat condition to higher parasite loads

A student works with a horse in the UConn stables
(c) Jason Sheldon / UConn)

Poor coat condition in horses has long been associated with heavy parasite burdens. A new
study from the University of Connecticut provides fresh evidence supporting this link and introduces a new tool to help assess it.

Led by Associate Professor Jenifer Nadeau in UConn’s Department of Animal Science, researchers developed a skin and coat condition scoring system to evaluate horses alongside their parasite levels. The work, published in the Journal of Equine Veterinary Science, builds on ideas that suggest that outward appearance may reflect an animal’s parasite resistance.

In the study, UConn’s herd of Morgan and Thoroughbred horses was regularly evaluated by students as part of the university’s hands-on equine science program. Faecal egg counts were collected to measure strongyle parasite loads, while separate teams of students, blinded to those results, scored each horse’s skin and coat condition.

The findings showed a clear trend: horses with higher parasite loads were significantly less likely to have good hair lustre. Although factors such as breed, age, housing, and season also influenced coat condition, parasite burden remained a strong predictor. Thoroughbreds, for example, tended to score lower than Morgans across several skin and coat categories.

The new scoring system may provide horse owners, managers, and even animal control agencies with a practical tool to help identify horses struggling with parasite-related issues or neglect. It can complement existing faecal testing by offering a quick visual assessment that may signal when further investigation is needed.

Nadeau plans to continue investigating how parasite levels change throughout a horse’s life and how coat condition can be used as an additional indicator of health. The study reinforces a message well known to equine professionals: paying close attention to coat quality can provide valuable clues about what’s happening inside the horse.

For more details, see:

N. DeBel, J. Johnson, A. Simoneau, B. Sweeney, G. Stearns, M. Amalaradjou, E. Gibbs, T. Moore, J. Nadeau,

The effect of parasitic load on skin and hair coat condition in Morgan and Thoroughbred horses,

Journal of Equine Veterinary Science, (2025) Vol 148, 105546

 

https://doi.org/10.1016/j.jevs.2025.105546

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Study on Deworming Practices

 The University of Connecticut Equine Extension Program has announced a study to better understand how horse owners and equine professionals manage deworming. Through a brief 10-minute survey, the team aims to gather real-world insight into current parasite-control practices and the industry’s overall awareness of effective deworming strategies.

Participation is voluntary, and all responses will remain confidential and used solely for educational purposes. The survey asks for basic information about respondents’ horses and their deworming experiences. Once started, answers cannot be revisited, and participants may stop at any time.

Those interested in contributing to this research can complete the survey at: https://s.uconn.edu/deworming-survey

300,000-year-old equine genomes reveal deep roots of modern horses

The fossilised remains of horses found
next to hunting spears at Schöningen
. (c) Nicholas Conard

  For the first time, scientists have reconstructed the genomes of an extinct horse species, Equus mosbachensis, that lived around 300,000 years ago in what is now Lower Saxony, Germany. The achievement, announced by researchers from the Senckenberg Centre for Human Evolution and Palaeoenvironment at the University of Tübingen and the Schöningen Research Centre, represents a breakthrough in the study of horse evolution.

Thanks to exceptionally favourable preservation conditions at the archaeological site of Schöningen, the team was able to extract the oldest DNA ever recovered from an open-air site, pushing back the known survival limit of ancient DNA beyond 240,000 years. Their findings, published in Nature Ecology & Evolution, reveal that the Schöningen horses belong to a genetic lineage that ultimately gave rise to all modern horses.

Modern domestic horses, along with donkeys and zebras, all belong to the genus Equus, the sole surviving branch of a family that once included over 35 genera and hundreds of now-extinct species. Fossils trace the equine family tree back around 55 million years, making it one of the most thoroughly studied lineages in evolutionary history.

“This family is one of the most thoroughly researched animal groups in evolutionary history. Their fossils can be traced back over a period of around 55 million years,” explains Prof. Dr. Cosimo Posth from the Senckenberg Centre for Human Evolution and Palaeoenvironment at the University of Tübingen, 

He continues, “For a long time, genetic research focused primarily on changes caused by the domestication of horses in the recent past. But to understand the evolution of the horse, yoflssilu also have to examine their earlier history. Archeological finds, for example, show that horses already played a central role for early human species, particularly as a source of food.”

Arianna Weingarten, doctoral researcher and the study’s first author explains, “Schöningen is famous for its wooden spears which date back around 300,000 years ago and are the oldest known complete hunting weapons in the world.”

“The fossil remains of at least 20 hunted horses were found right next to the spears. Impressive evidence of the close relationship between humans and horses long before they were domesticated,” she added. Our study’s aim was to clarify the position and origin of Equus mosbachensis in the equine family tree and to better understand the genetic relationship to today’s horses.”

Recovering DNA from material this old, and from an open-air site rather than a cave or permafrost, is a major technical leap. Normally, exposure to oxygen, microbes, and temperature fluctuations destroys genetic material over time. But at Schöningen, the horse bones had lain preserved in waterlogged, low-oxygen sediments, creating natural conditions that shielded the DNA for hundreds of millennia.

Using carefully selected samples from the dense inner portions of petrous bones (a part of the skull known for its DNA protection) and new bioinformatic methods, the team reconstructed two largely complete mitochondrial genomes.

“Until now, it was found that DNA could only be preserved for a maximum of around 240,000 years outside caves or permafrost. The Schöningen horses now push back this limit significantly,” says co-author Häusler. She continues, “Normally, DNA decays quickly in open air contexts because temperature changes and microbes destroy the genetic material. But in Schöningen, the bones were preserved in permanently moist, low-oxygen sediments. This unique environment likely acted as natural protection.”

The genetic analysis revealed that the Schöningen horses fall within a lineage ancestral to all modern horses, including today’s domestic breeds. This finding bridges a long-standing gap between early fossil horses and the animals that eventually spread across Eurasia and North America.

Over the course of horse evolution, Equus ancestors repeatedly crossed the Bering Land Bridge between Asia and North America. Two major migration waves are known: the first, around 2.6 million years ago, led to the ancestors of today’s zebras and donkeys; the second, about 900,000 years ago, brought the so-called “caballine” horses — the group from which modern horses ultimately descend.

Many branches of this family tree, including Equus mosbachensis, later went extinct. But the Schöningen DNA shows that their genetic legacy continued.

“With our study, we were able to fill a temporal and geographic gap in the study of horse evolution,” says Posth.  “Our results also show that surprisingly even in seemingly unfavourable environments, such as open-air excavation sites, extremely ancient DNA can still survive and be recovered. This opens up the possibility of extending our method to other species, thereby uncovering the genetic diversity of the distant past.” 

Such studies also remind us how long the human–horse connection has existed. While domestication didn’t occur until around 5,500 years ago, the Schöningen find shows that humans were already interacting closely with horse populations hundreds of thousands of years earlier. 

For more details, see:

Arianna Weingarten, Meret Häusler, Jordi Serangeli, Ivo Verheijen, Ella Reiter, Rita Radzevičiūtė, Alexander Stoessel, Johannes Krause, Maria A. Spyrou, Nicholas J. Conard, Kay Nieselt & Cosimo Posth.

Mitochondrial genomes of Middle Pleistocene horses from the open-air site complex of Schöningen. 

Nat Ecol Evol (2025). 

https://doi.org/10.1038/s41559-025-02859-5

Study reveals multiple factors influence stress in dressage horses

Dr Sebastian McBride. (c) Jay Williams

A new study from Aberystwyth University and the University of Portsmouth has shown that the type of bridle worn by a horse in dressage competition is not the sole factor affecting signs of stress. While the use of a two-bit double bridle has often been debated in terms of welfare, the research reveals that stress indicators in horses are influenced by a complex combination of factors including rider skill, head position, and training practices.

The study, published in the journal Animals, investigated the behaviour of 135 horses across a range of dressage competitions. Researchers recorded a range of conflict behaviours (observable actions that indicate discomfort or acute stress) such as tail swishing, head tossing, and mouth opening. These behaviours were common among the horses studied, regardless of whether they were ridden in a double or snaffle bridle.

 

To understand these responses more deeply, the team also examined other potential influences: the level and type of competition, the angle of the horse’s head when ridden, and the use of additional tack items such as the noseband, cheekpiece type, spurs, and ear bonnets. Using a detailed behavioural ethogram and advanced statistical analysis, the researchers identified nine main behavioural components and explored how these related to the different variables.

 

The results revealed a complex relationship between bridle type, rider skill level, and ridden head angle. For example, horses ridden with double bridles did not necessarily display higher levels of stress, suggesting that how the bridle is used, and the rider’s ability to use it sensitively, plays a crucial role. Across all horses observed, mouth opening occurred in 100% of cases and tail swishing in 86.7%, highlighting the prevalence of conflict behaviours in competitive dressage generally.

 

Dr Sebastian McBride, senior lecturer in animal behaviour at Aberystwyth University and co-author of the study, said:“This research challenges the simplistic narrative that double bridles are inherently more harmful. What we found is a much more nuanced picture—bridle type interacts with rider skill, horse training, and even the horse’s head position during performance. It’s not just about the tack, but how it’s used and the rider using it.”

 

The findings arrive at a time of increasing public scrutiny over animal welfare in equestrian sport. At higher levels of dressage, the use of a double bridle is still mandatory - a rule that continues to spark debate among riders, trainers, and welfare advocates. The new evidence suggests that focusing on the equipment alone oversimplifies what is clearly a multifaceted welfare issue.

 

The researchers emphasise the importance of behavioural observation as a tool for assessing horse wellbeing. By identifying and analysing patterns of behaviour that signal discomfort, the study offers a foundation for future research into how competitive settings and rider techniques affect equine mental states.

 

Dr McBride added: “Trying to assess horses’ mental wellbeing is complex and needs a focus on the evidence. Our study adds to a growing body of research that supports more informed, welfare-conscious decision-making in equestrian sport.”

 

The research team also included Aberystwyth University graduates Rifka Faithfull and Emily Drury, alongside Dr Kate Lewis from the Centre for Comparative and Evolutionary Psychology at the University of Portsmouth.

 

In summary, the research highlights that bridle type alone does not determine a horse’s stress level in dressage. Instead, it is part of a wider picture involving how the horse is trained, ridden, and managed. Continued investigation into these complex interactions will be key to improving welfare standards in equestrian disciplines.

 

For more details, see: 

 

Faithfull, Rifka, Kate Lewis, Emily Drury, and Sebastian McBride. 2025. 

Influences of Double Versus Snaffle Bridles on Equine Behaviour at Dressage Competitions and Factors That Interact with Their Effect.

 Animals15, no. 12: 1782. 

https://doi.org/10.3390/ani15121782

Blue light influence on PPID

Pituitary pars intermedia dysfunction (PPID) affects approximately 21% of the aged equine
population and is characterised by excessive hair growth, delayed shedding, and metabolic disturbances. While pergolide is the standard therapy, some horses continue to exhibit coat abnormalities and lethargy. Seasonal regulation of hair growth is photoperiod-dependent, and previous research has demonstrated that exposure to blue light can influence coat shedding. 

A study by Sinead Parmantier and colleagues in Ireland and Kentucky examined whether extending day length using blue light masks could enhance coat condition and reduce PPID-associated signs when used alongside medical management. A full report of the study is published in Animals.

Fifty-two horses (>15 years) with a veterinary diagnosis of PPID and visible hypertrichosis were recruited via an online owner survey.

The horses were assigned to treatment and control groups. The treatment group (n = 29) wore Equilume® blue light masks from mid-December, extending their daily photoperiod to 15 hours. The control group (n = 23) experienced the natural seasonal light–dark cycle. Because most of these horses (44 out of 52) were receiving daily pergolide medication for PPID, a second unmedicated control group (n = 17) comprising research horses in the USA was included. These horses were maintained under natural photoperiod conditions for the 13-month study period.

Hair length, shedding, and body condition were measured monthly. Owners of groups T and C1 completed bimonthly questionnaires on coat condition, fat coverage, energy, and other PPID symptoms. Data were analysed using linear mixed models and non-parametric tests to assess effects of time, group, and group × time interactions.

There was no difference in hair lengths between the blue-light-treated and the first control group, but the second control group had shorter hairs. Shedding started a month earlier in the spring for the blue light group. Owners’ questionnaires revealed better coat condition in April, reduced fat coverage in April and June, and more energy in February for the blue light group.

In a final assessment, treatment-group horses showed significant improvements in coat condition, PPID clinical signs, and perceived quality of life.

Although blue light treatment did not significantly alter overall hair length compared to medicated controls, it advanced shedding and improved clinical signs of PPID. 

These results align with previous findings that artificial photoperiod extension can influence hair follicle activity. Owner-reported outcomes indicate improved welfare, though the potential for observer bias warrants caution. The consistent positive trend suggests that blue light may act synergistically with pergolide, helping to mitigate coat-related symptoms and enhance comfort in PPID horses.

Extended photoperiod achieved via blue light masks advanced spring shedding and improved coat condition, energy, and perceived wellbeing in PPID horses. 

Blue light therapy shows promise as a complementary, non-invasive management strategy alongside conventional medication. Further controlled research is warranted to clarify the physiological mechanisms and optimise treatment protocols.

 

For more details, see:

Parmantier, Sinead, Panoraia Kyriazopoulou, Margaret McClendon, Amanda Adams, and Barbara A. Murphy. 

Influence of Extended Photoperiod Using Blue Light Masks on Hypertrichosis, Coat Condition and General Health Parameters in Horses with Pituitary Pars Intermedia Dysfunction" 

Animals (2025) 15, no. 19: 2905. 

https://doi.org/10.3390/ani15192905

Cardiology focus for latest EVJ virtual issue

Exercising ECG an important element of
cardiac assessment in sport horses. (EVJ)

 The latest Equine Veterinary Journal virtual issue brings together new research on equine
cardiac physiology, diagnostics, and management, with a focus on atrial fibrillation (AF). 

The collection, guest edited by Laura Nath and Vicky Savage, is free to read until 7 January 2026 and features 20 papers, including an editorial overview of current advances and ongoing challenges in equine cardiology.

Highlights include:

• Atrial fibrillation (AF): Recent progress in diagnosing and managing this common cause of poor performance in horses.

• Arrhythmia monitoring: Studies using implantable loop recorders and wearable ECG devices to detect AF and other rhythm disturbances during exercise.

• Exercise and heart rate: Links between peak heart rate, heart rate variability, fatigue, and the occurrence of arrhythmias—particularly in event horses during cross-country phases.

• Associated conditions: Connections between cardiac arrhythmias, upper respiratory obstructions, and exercise-induced pulmonary haemorrhage.

• Predicting AF recurrence: Use of atrial premature depolarisations and atrial fibrillatory rate to assess recurrence risk.

• Cardiac anatomy: Structural variations such as accessory valve leaflets that can influence imaging interpretation.

• Mapping and ablation techniques: Advances in 3D electro-anatomical mapping and ablation of arrhythmogenic tissue in standing horses, showing the feasibility of trans-septal approaches.

Laura Nath said the collection “improves our understanding of arrhythmogenic mechanisms and diagnostic approaches,” while Vicky Savage added that it “offers practical, evidence-based support to equine vets for diagnosing and managing cardiac disorders.”

For more details, see:

https://beva.onlinelibrary.wiley.com/doi/toc/10.1001/(ISSN)2042-3306.current-progress-in-equine-cardiology

Early-life management linked to racing success in Thoroughbreds, RVC study finds

(c) Tania Penderakis Dreamstime.com

Recent research conducted by the Royal Veterinary College (RVC) has shown that
Thoroughbred foals given extensive turnout in larger pastures during their first six months of life, and those weaned at an older age, are more likely to enter training, race more frequently, and earn greater prize money later in life.

The study provides new insight into how gestational and early-life management can influence the growth, development, and long-term athletic performance of racehorses. It aimed to enhance understanding of how early-life health and husbandry practices affect both racing outcomes and the financial sustainability of Thoroughbred breeding enterprises.

According to the research team, this is the first UK-based field study to comprehensively evaluate the effects of early-life exposures, particularly exercise and turnout, on later-life milestones and race performance in Thoroughbreds. The findings offer direct practical applications for stud farms, supporting both horse welfare and industry retention, in line with the Horse Welfare Board’s strategy for improving the welfare of racehorses.

The research, led by Dr Rebecca Mouncey, Post-Doctoral Research Fellow at the RVC, was conducted as a prospective cohort study. The team followed 129 flat-race bred Thoroughbred foals, born in 2019 and 2020 on six stud farms across the UK, from birth through to training and early racing careers.

Detailed data were collected on each dam’s reproductive history and health during pregnancy, alongside daily records of foal management, health status, turnout duration and area, and any veterinary-attended illnesses or injuries. These records were maintained until the foals left their stud farms or exited the study. Racing performance data were subsequently collated from industry databases up to the horses’ fourth year of life.

Statistical analyses, including mixed-effects logistic and linear regression models (with farm, mare, and stallion as random effects), were used to examine associations between gestational and early-life exposures and later racing performance.

Of the 129 horses studied, 76% (98/129) went on to race by the age of four, with a median of seven starts (interquartile range [IQR] 4–11) and median prize earnings of £6,898 (IQR £1,712–£17,987).

Significant associations were identified between early-life management factors and later performance:

• Turnout: Foals that spent more time turned out at pasture during their first six months of life were more likely to race and earned more prize money.
• Increasing average daily turnout time and pasture size were associated with higher odds of racing (Odds Ratio 1.31, 95% CI: 1.09–1.58, p = 0.004) and increased total prize earnings (β = 0.32 lnGBP, 95% CI: 0.03–0.61, p = 0.03).

• Weaning Age: Foals weaned later were more likely to race and made a greater number of race starts.
• Each additional day of age at weaning increased both the odds of racing (OR 1.03, 95% CI: 1.01–1.05, p < 0.05) and total number of runs (β = 0.09, 95% CI: 0.04–0.14, p < 0.05).

These results indicate that management during the first six months of life plays a critical role in preparing Thoroughbreds for future athletic success.

The findings demonstrate that early-life turnout and weaning practices significantly affect race participation, performance, and financial outcomes. Providing foals with ample turnout opportunities and delaying weaning until after this key developmental window may support positive musculoskeletal adaptation and improved future performance.

Dr Mouncey noted that: “This study is the first of its kind to evaluate the impact of early-life experiences on later racing performance in Thoroughbreds. Our findings highlight that the first six months of life represent a crucial developmental period in which management practices must promote optimal tissue development and welfare.”

The study was funded by the Horserace Betting Levy Board, the Racing Foundation, and the RVC’s Mellon Fund for Equine Research, and is published in the Equine Veterinary Journal.

For more details, see:

Mouncey R,  de Mestre AM,  Arango-Sabogal JC,  Verheyen KL.  

Born to run? Associations between gestational and early-life exposures and later-life performance outcomes in Thoroughbreds. 

Equine Vet J. (2025).

 https://doi.org/10.1111/evj.70084

Researchers seek horses for PPID treatment response study

  A research team from the University of Minnesota is urgently seeking horse owners and veterinarians to participate in a study on pituitary pars intermedia dysfunction (PPID), more commonly known as equine Cushing’s disease.

PPID affects up to 30% of older horses, causing a range of problems, from poor performance to severe illness and even death. The disease occurs when neurons in the hypothalamus are damaged, disrupting the brain’s ability to regulate the pars intermedia region of the pituitary gland. While there is no cure, treatment focuses on managing symptoms and slowing progression.

The most widely used treatment is pergolide which helps compensate for the dopamine loss seen in affected horses. Originally developed for Parkinson’s disease in humans, pergolide remains the only FDA-approved drug for PPID in horses.

However, horses vary widely in how they respond to this medication. Studies show that 60 - 80% of horses respond well, but definitions of “success” differ. Moreover, adverse effects are common. Anorexia is reported in up to 32% of treated horses, alongside issues like colic, weight loss, and behavioural changes. These side effects often lead owners or veterinarians to reduce or stop treatment, allowing the disease to worsen.

In human medicine, it is well established that genetic differences can influence how individuals respond to drugs. Researchers now believe the same may be true for horses.

To explore this, Dr. Molly McCue and Dr. Lauren Hughes of the UMN Equine Genetics and Genomics Laboratory, together with Dr. Dianne McFarlane at the University of Florida, are leading a study to identify genetic factors that influence pergolide response and side-effect risk in horses with PPID.

“Our goal is to identify genetic variants that influence treatment outcomes,” explain the researchers. “If we can find alleles that predict poor response or higher risk of adverse effects, we could tailor dosing and treatment to each horse, making therapy safer and more effective.”

Dr. Hughes adds, “As a veterinarian, I’ve seen how devastating PPID can be for horses and their owners. This research could help us greatly improve diagnosis, treatment, and management of this disease.”

The team is seeking horses diagnosed with PPID by a veterinarian - confirmed through bloodwork - who have been on pergolide therapy for at least six months. They are particularly interested in horses that:

·       Require higher or more frequent doses of pergolide

·       Experience adverse effects such as appetite loss, weight loss, colic, or behavioural changes

Eligible horses should:

·       Be 15 years or older at the time of diagnosis

·       Have clinical signs consistent with PPID (e.g. long, shaggy coat, muscle loss, dullness, or recurrent infections)

·       Have had follow-up blood tests (ACTH, TRH stimulation, or dexamethasone suppression tests)

Participation involves submitting medical records and providing hair root or blood samples. Owners may enrol as many horses as they wish.

The researchers emphasise that participation is vital: by contributing samples and data, owners will help uncover the genetic clues that could shape the future of personalised PPID treatment - offering hope for safer and more effective therapies for horses everywhere.

For more details, see: 

https://vetmed.umn.edu/equine/research/equine-genetics-and-genomics-laboratory/projects/equine-pituitary-pars-intermedia-dysfunction-ppid/pergolide-study

 

https://www.youtube.com/watch?v=kZl2WvUBt1w