Promising use of stem cells for tendon injuries in flat racehorses

Research from Australia suggests that treatment with bone marrow derived mesenchymal stem cells (BM
MSCs) results in improved healing compared with a controlled exercise rehabilitation program alone. 

 Strain of the superficial digital flexor tendon (SDFT) injury is one of the most common and significant injuries in racehorses. The tendon plays a crucial role in the movement and stability of a horse's limb, particularly during high-speed activities like racing. 

 The primary treatment is rest, often for months, to allow the tendon fibres to heal. Full recovery can take over a year, but even then, the tendon may remain weaker and more prone to re-injury, especially if the horse returns to high-intensity activities. Tendons have a limited ability to regenerate, and the damaged fibres are often replaced by scar tissue, which is mechanically inferior and increases the risk of future injury. 

 Research by Rachel O. Salz and colleagues investigated how SDFT (superficial digital flexor tendon) injuries in Thoroughbred racehorses respond to different treatments. They compared the effects of a controlled exercise recovery program alone with those of the same program combined with either autologous bone marrow-derived stem cells (BM-MSCs) or allogenic adipose-derived stem cells (A-MSCs). (Autologous stem cells are taken from the same individual receiving the treatment. Allogenic stem cells come from a donor) 

 The study analysed clinical and race records of 213 Thoroughbreds to see if stem cell treatments improved the chances of horses returning to racing compared to just using the exercise recovery program.  

One group of horses followed a controlled exercise rehabilitation program (CERP) without stem cell treatment, while another group followed the CERP with additional treatment using either BM-MSCs or A-MSCs injected into the damaged tendon. 

The study found that horses treated with intralesional bone marrow-derived mesenchymal stromal cells were three times more likely to return to racing compared to those undergoing only the controlled exercise rehabilitation program. Additionally, these horses were at least twice as likely to participate in five or more races after returning, indicating that the treatment had a lasting impact beyond just recovery. 

 In contrast, the response to adipose-derived mesenchymal stem cells (A-MSCs) was less encouraging. The analysis showed no significant increase in the likelihood of returning to racing or completing five or more races with A-MSC treatment compared to the rehabilitation program alone. However, the researchers noted that the smaller number of horses in this treatment group might have limited the ability to detect a potential effect. 

 For more details, see: 

 Treatment of racehorse superficial digital flexor tendonitis: A comparison of stem cell treatments to controlled exercise rehabilitation in 213 cases 

Rachel O. Salz, Christopher R. B. Elliott, Tomas Zuffa, Euan D. Bennet, Benjamin J. Ahern 

Equine Veterinary Journal (2023) Vol 55, pp 979-987 

https://doi.org/10.1111/evj.13922

EVJ presents growing evidence for regenerative medicine

Processing autologous conditioned serum
for intra-articular injection 
(photo courtesy of Lynn Pezzanite)

Regenerative therapies have become more widely used in equine practice over the past 20 years. They involve treatments that aim to repair or replace damaged tissues and promote healing using the body's natural regenerative capabilities. These therapies are increasingly used to treat injuries, particularly those affecting tendons, ligaments, joints, and cartilage.

 

Despite considerable advances in the field, the true efficacy of veterinary regenerative medicine is still questioned in many instances. To enable easy access to the latest knowledge on the topic, the Equine Veterinary Journal (EVJ) has published a ‘Special Collection’.

Guest edited by Lynn Pezzanite, the Special Collection contains the ‘Top 10’ recent publications from EVJ relating to regenerative therapies over the past five years which may help practitioners select one treatment over another for a specific clinical indication.

 

The term ‘regenerative therapies’ is a broad definition for innovative medical therapies that enable the body to repair, replace, restore, and regenerate damaged or diseased cells, tissues, and organs, while ‘biological products’ are those made from living material (human, animal, plant, microorganisms) used to treat or prevent disease. 

 

Options available to clinicians in equine practice include point-of-care blood or tissue derived products (autologous – derived from the same individual) including platelet rich plasma (PRP), autologous conditioned serum (ACS or interleukin receptor antagonist protein/IRAP), autologous protein solution (APS), bone marrow aspirate concentrate (BMAC or stromal vascular fraction) or cultured stromal cell-based products (autologous or allogeneic – derived from a different individual of the same species). 

 

“Equine practitioners have access to use regenerative medicine to treat joint and soft tissue disorders as well as a variety of other conditions such as wounds, ophthalmic or theriogenology indications,” said Lynn. “However, in some instances due to lack of rigour in clinical study design, lack of demonstrated consistency in product formulation and lack of regulatory oversight that would assure appropriate standards, the true efficacy of some therapies remains controversial. We aim for this special collection to bring some clarity, to aid vets in their treatment choices.”

 

To see the Special Collection, go to::

 

https://beva.onlinelibrary.wiley.com/hub/journal/20423306/homepage/regenerative-therapies-collection

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 

Horses smarter than previously thought, study suggests

Horses are more intelligent than previously believed, according to a new study that shows how they cleverly adapted their behaviour to maximise rewards with minimal effort.  

Researchers at Nottingham Trent University sought to understand more about equine learning processes, as this knowledge could lead to more humane training methods and improved welfare for horses. A full report of the study is published in the journal  Applied Animal Behaviour Science. 

 

The study involved twenty horses, aged 11 to 22 years, including seven females and thirteen castrated males of mixed breeds. 

 

The team devised a task where horses had to touch a piece of card with their nose to receive a treat. They then made the task more challenging. Horses would not get a treat if they touched the card while a bright white “stop” light was on but would do if they touched it while the light was off.

 

 As the task was made more challenging, the horses initially struggled, indiscriminately touching the card whether a light was on or off, though they continued to receive rewards for correct responses.

 

In the final stage, a penalty was introduced: touching the card when a “stop” light was on resulted in a ten-second timeout during which no rewards could be earned. Remarkably, the horses quickly adapted, showing a significant reduction in errors and only touching the card at the correct times to receive treats.

 

The researchers suggest that rather than misunderstanding the game, the horses may have understood it all along but found a way to play that required less attention. They suggest that their findings indicate a higher level of cognitive processing than was previously thought possible, as the horses instantly switched strategies when faced with the risk of losing rewards. 

 

This approach requires the horse to think into the future, the researchers say, and is very goal directed, with horses required to focus on what they want to achieve and the steps they need to take to do this. 

This, they argue, is something which has previously been considered beyond a horse’s cognitive capacity.

“At first we found that horses would just keep touching the card over and over, as they probably realised they would still get a frequent reward with minimal mental effort,” said lead researcher Dr Carrie Ijichi. 

She said: “There was no cost for indiscriminate hitting, sometimes it paid off, sometimes it didn’t. When we introduced a cost for their errors, however, they could instantly understand and play the game properly. 

“Horses are not natural geniuses, they are thought of as mediocre, but this study shows they’re not average and are in fact more cognitively advanced than we give them credit for. 

“We now think that horses may be able to use a form of learning called ‘model-based learning’ which was thought to be too complex for them. This will now help us to understand their behaviour and capabilities much better.

“It’s fascinating because they have a very underdeveloped pre-frontal cortex which is what we typically credit with producing that type of thinking in humans. This means they must be using another area of the brain to achieve a similar result and this teaches us that we shouldn’t make assumptions about animal intelligence or sentience based on whether they are ‘built’ just like us.”

Researcher Louise Evans, based in Nottingham Trent University’s School of Animal, Rural and Environmental Sciences, said: “We were expecting horses’ performance to improve when we introduced the time-out, but were surprised by how immediate and significant the improvement was. 

“Animals usually need several repetitions of a task to gradually acquire new knowledge, whereas our horses immediately improved when we introduced a cost for errors. This suggests that the horses knew all along what the rules of the game were.” 

For more details, see:

Louise Evans, Heather Cameron-Whytock, Carrie Ijichi,

Whoa, No-Go: Evidence consistent with model-based strategy use in horses during an inhibitory task,

Applied Animal Behaviour Science, (2024) Vol 277, 106339,

https://doi.org/10.1016/j.applanim.2024.106339

Edited press release

Effect of music on response to sudden and unexpected stimuli

Photo of audio cap attached
 to head collar. (c) Eyraud et al

The living conditions imposed on horses inevitably expose them to stress-inducing situations. 

Music appears to be a promising tool for managing such stress, although its benefits may diminish with repeated exposure. 

 

A study by Camille Eyraud and colleagues aimed to determine whether music could mitigate horses' reactions to unexpected stimuli and whether playing the same music daily reduces its effectiveness.

 

The research in, published in the International Journal of Equine Science, involved three groups of 12 horses, each led along a route with potentially stressful stimuli for 10 consecutive days. Each group wore headphones and was subjected to one of three conditions: a "music" condition with the same music track played, a "noise" condition with pink noise.

 

The authors explain: “Pink noise is a random signal with constant energy in the octave bands and is therefore weighted according to the properties of the human audiogram (and, by extension, also those of horses.)”

 

“The music was played directly into the horse's outer ear using an "audio cap" (see Figure 1).  This is a traditional earcap equipped with a pair of earphones in front of the pinnae and a pocket to hold a small MP3 player between the two ears.”

 

The findings indicated that music had a calming effect on both horse behaviour and heart rate in response to visual stimuli. Interestingly, the parameters for the pink noise condition were intermediate between those of the music and no-music conditions. 

 

Regarding the potential loss of music's effectiveness with repeated exposure, the study showed that music continued to mitigate stress-related behaviours effectively for up to seven consecutive exposures, although this effect was not consistent every day.

 

In conclusion, music can enhance human-horse interactions by reducing horses' stress in unexpected situations. The study also showed that the use of music did not interfere with the horses' awareness of and response to environmental noise, which is crucial in case of real danger.

 

However, the researchers suggest that to maintain music's efficiency, it should be used sparingly to target specific, time-limited events. They question whether playing music continuously throughout the day, as is often done in stables, might be counterproductive.

 

However, the researchers suggest that to maintain music's efficiency, it should be used sparingly to target specific, time-limited events. They question whether playing music continuously throughout the day, as is often done in stables, might be counterproductive.

 

They recommend further research to understand the mechanisms behind this effect and to ensure its safe and consistent application in practical settings.

For more details, see:

 

Eyraud, C., Valenchon, M., Cairo, M., Adam, O. and Petit, O. 2024. 

Can Repeated Exposure to Music Mitigate Horses’ Reactions to Sudden and Unexpected Stimuli?. 

International Journal of Equine Science. 3, 1 (Apr. 2024), 58–65.

https://rasayely-journals.com/index.php/ijes/article/view/102

Optimising Youngstock Growth and Development

 An international panel focused on "Optimising Youngstock Growth and Development" at the Gerald Leigh Lectures on June 12, 2024. 

Organized by the Beaufort Cottage Educational Trust on behalf of the Gerald Leigh Charitable Trust, the event honours Mr. Leigh’s accomplishments as a racehorse owner and breeder and his dedication to scientific knowledge and horse welfare. The speakers included experts from the UK, USA, and Europe.

 

Key topics included:

·      Influence of prenatal maternal and environmental factors on foal athletic potential (Pascale Chavatte-Palmer, France)

·      Seasonal effects on mare and foal nutrition (Joe Pagan, USA)

·      Overview of foal purchase at public auctions (Jamie Railton)

·      Parasite resistance on UK stud farms and parasite control strategies (Professor Jacqui Matthews and Paul Overton)

·      Sustainable equine helminth control (Professor Jacqui Matthews)

·      Surgical solutions for limb deformities (Abigail Kent)

·      Raising foals for optimal performance (Dr. Rebecca Mouncey)

·      A stud manager's approach to soundness (Julian Dollar)

·      Balancing youngstock growth and development (Joe Pagan).

 

To watch recordings of the lectures (and those from previous years) go to:

 

https://www.beaufortcottage.com/news-events/category/gerald-leigh-memorial-lectures/

Movement sensors help identify horses at risk of injury

A sensor worn in the saddle cloth may help reduce the risk of catastrophic injury in racehorses. 
 

Researchers, led by Warwick Bailey at Washington State University, have been working with the biometric sensor, developed by the company Stride Safe, to monitor Thoroughbred racehorses during racing and training.

 

By analysing the collected data, the team identified subtle stride changes linked to a increased risk of injury, enabling interventions before catastrophic breakdowns occurred. The researchers highlighted three horses flagged in 2023 at Churchill Downs in a report published in the Journal of the American Veterinary Association.

 

The sensor tracks changes in the rate and direction of a horse's leg and body movements, generating graphs of its stride pattern. An algorithm processes this data and compares it to an "ideal stride" derived from high-performing, sound racehorses. Using data from over 6,500 starts, the algorithm also identifies similarities with strides from horses that suffered catastrophic injuries. The horse is then assigned an injury risk factor from 1 to 5, based on how much its stride deviates from the ideal and how similar it is to an injury-associated stride.

 

Risk status was categorized from 1 to 5. Horses with a risk factor of 1 had a stride pattern within 2 standard deviations (SDs) of the ideal stride, while those with a risk factor of 5 had a stride pattern more than 5 SDs from the ideal stride. Horses with a risk factor of 5 were 950 times more likely to suffer a catastrophic injury than those with a risk factor of 1. 

 

In a database of 6,618 starts, 70% were categorized as risk factor 1, 16.5% as risk factor 2, 7% as risk factor 3, 3% as risk factor 4, and 3.5% as risk factor 5.

 

“These racehorses get extensive examinations before races, but catastrophic injuries still happen, and not because they stepped in a hole or took a bad step. A large percentage have a pre-existing pathology not readily apparent on clinical examination,” said Dr. Denise Mc Sweeney, an equine surgery resident at WSU who was the first author on the study. “From our sensor data, we know most catastrophic injuries have a distinct stride pattern. Now we can see when there's something wrong with their strides and step in before a major injury occurs.”

 

“We know there are about 1.25 catastrophic injuries per 1,000 starts, but identifying those horses before such an event occurs is like finding a needle in a haystack, as they are often subjectively sound during a pre-race examination, and many don’t show any decrease in performance,” Mc Sweeney said. “But if you can narrow it down, like the 3.5% we had out of that group, it is a lot easier to intervene and hopefully prevent injuries.”

 

To test and refine the algorithm, a sensor was placed on horses starting at Churchill Downs and Ellis Park in Kentucky from April 29 to July 2, 2023. Mc Sweeney was responsible for collecting clinical data on the high-risk horses.

In their report, the team focused on a pair of 3-year-old colts and a 4-year-old stallion flagged as category 5. 

 

In each instance, the sensors alerted veterinarians and trainers to potential injury risks.  The abnormal stride pattern was detected either during racing (cases 1 and 2) or while breezing (case 3) (a training run where the horse is allowed to run at a swift pace, often close to its maximum speed)

 

Subsequent veterinary examinations and 18F-sodium fluoride (18F-NaF) positron emission tomography were conducted in each case. The research team discovered significant 18F-NaF uptake in the condyles of the third metacarpal bone in cases 1 and 2, identifying these horses as being at increased risk for condylar fractures. In the third case, the 18F-NaF uptake pattern indicated that the third carpal bone was likely causing the horse’s lameness. Radiography confirmed an impending slab fracture.

 

The researchers report that “following periods of convalescence, cases 1 and 2 returned to racing and were identified by the sensor system as no longer being at high risk of catastrophic musculoskeletal injury. Case 3 returned to training but has yet to return to racing.”

 

“These are prime examples of how this technology can prevent horses from breaking,” Mc Sweeney said. “With this information, the trainers and their vets were able to put the brakes on, and now these horses are going on to have longer careers and, hopefully, avoid a catastrophic injury.”

 

Mc Sweeney is hopeful the sensors will become standard for all thoroughbred racing and training. “I believe this is going to make a huge impact,” she said. “The sensors can save the lives of horses and jockeys – they already have.”

 

 

For more details, see: 

 

Using accelerometers to identify a high risk of catastrophic musculoskeletal injury in three racing Thoroughbreds

Denise Mc Sweeney DVM, MS,  Mikael Holmström DVM, PhD, Kevin D. Donohue PhD , David H. Lambert BVSc, and Warwick M. Bayly BVSc, PhD, DACVIM  

 

https://doi.org/10.2460/javma.24.02.0114

 

See also: https://www.stridesafeusa.com

Fascinating Fascia

Horses Inside Out has released details of a series of courses coming up in September,
presented by Gillian Higgins.

 

Discover More About Fascinating Fascia! (1st September – Online)

 

Healthy fascia is vital for a healthy horse. Understanding the fascial system is crucial for riders, trainers, and equine therapists. Fascia impacts posture, movement, force transmission, proprioception, reflexes, energy, sensation, and potentially the horse’s emotions. Proper hydration of fascia is essential for its function and the overall musculoskeletal health of the horse.

 

This seminar is open to anyone interested in learning more about fascia for the benefit of their horse.

 

Developing Palpation (5th & 6th September)

 

A practical 2-day course designed to improve palpation skills and techniques. Participants will revise anatomy knowledge, learn new techniques, and practice on various horses to refine their skills.

 

Fascia Release Techniques (9th & 10th September)

 

This course delves into the anatomy of different types of fascia, their connections, functions, dysfunctions, and maintenance. Participants will learn and practice various palpation and fascia release techniques over two days.

 

Joint Mobilisations (12th & 13th September)

 

Learn to assess subtle changes and recognize abnormalities in soft tissues and joints. The course covers musculoskeletal testing and appropriate mobilisation techniques.

 

For all the details, see: 

 

https://www.horsesinsideout.com/whats-on-list

Ontario riding schools sought for research study

 Do you run a riding school within three hours of Guelph, Ontario? If so, you may be able to play
a part in a forthcoming study at the University of Guelph aimed at identifying strategies to help riding school horses thrive.

The researchers, led by Dr Katrina Merkies in the. Department of Animal Biosciences, are seeking 23 hunter/jumper lesson establishments, each with a minimum of four horses, to volunteer their facilities for data collection in the study. 

They assure that the study will have no impact on the day-to-day running of the school. Participants will receive a $100 honorarium.

 

If interested, please contact the research team for more details on how to participate.

 

Contact kmerkies@uoguelph.ca or ccopelin@uoguelph.ca for more information or 

register online

New internal parasite guidelines from AAEP

The American Association of Equine Practitioners (AAEP) has issued revised Internal Parasite Control Guidelines to help minimise the risk of parasitic disease and maintain the effectiveness of current drugs for as long as possible by delaying further development of anthelmintic resistance.

The guidelines, originally created in 2013 and last revised in 2019, account for recent advances in knowledge concerning increased anthelmintic resistance and optimisation of parasite control management practices. They also address common misconceptions and offer parasite control program recommendations for senior horses (over 15 years old), mature horses (between 5 and 15 years old), and young horses (under 5 years old).

The guidelines were reviewed and updated by the AAEP Internal Parasite Control Guidelines Task Force, chaired by Dr. Nielsen and comprised of 10 AAEP members predominantly board certified in veterinary internal medicine, veterinary parasitology and/or veterinary microbiology. 

“We have seen dramatic development in the field of equine parasite control over the past 10 years, since we first launched these guidelines, and we work hard to keep our recommendations up to date,” said Martin Nielsen, DVM, PhD, DVSc, DAVCM, DEVPC, Schlaikjer Professor of Equine Infectious Diseases at the University of Kentucky.

Important conclusions to be drawn from the revised guidelines are to:

• Perform fecal egg count reduction tests annually to ensure that you are using effective dewormers in every herd or barn.
• Recognize that no anthelmintic will eliminate all parasitic stages from a horse.
• Continue using fecal egg counts once or twice per year to stratify horses into low, medium and high shedders to reduce pasture contamination.
• Deworm all horses at a baseline rate and target selected horses more often based on fecal egg counts.
• Not use fecal egg counts to diagnose disease in horses as there is no correlation between fecal egg counts and disease-causing parasite life stages.
• Discontinue deworming all horses with fixed intervals year-round and stop blindly rotating anthelmintic classes.

View the guidelines at https://aaep.org/resource/internal-parasite-control-guidelines.

You can access the entire guidelines document by clicking the Download Resource button.

Memory for dung sniffing

Horse dung (c) Avrezn Dreamtime.com

 Horses sniff dung for several reasons - for communication, social behaviour, and environmental awareness.  

Dung contains chemical cues that can convey information about the individual who deposited it, such as their identity, sex, and reproductive status. By sniffing dung, horses can recognize and gather information about other horses in their vicinity. It may also help horses understand social structures and hierarchies within a group, allowing them to recognize dominant individuals and avoid potential conflicts.

 

Horses may form "stud-piles" where they deposit dung in specific locations to mark their presence. This behaviour can communicate territorial boundaries or indicate that a particular area is frequently used by certain individuals or groups

 

Research by Audrey EM Guyonnet, and Ian Q. Whishaw, at the Canadian Centre of Behavioural Neuroscience, University of Lethbridge, Alberta looked at how horses use location , odour, and memory related to their encounters with dung.

 

In their study, which is reported in Behavioural Processes, they assessed the response of horses when they were led, at varying time intervals, to objects chosen by the experimenter or to dung deposits, which they were allowed to sniff.

 

Twenty-two horses were included in the study. which was carried out in a total of six riding arenas—two indoor and four outdoor. – 

 

The research team took video recordings of the horses encountering the objects and the dung Frame-by-frame video analysis assessed several factors: the way the horses approached the objects or dung deposits, the duration of sniffing, nostril use, ear position, and blinking associated with dung investigation.

 

The researchers found that horses consistently approached and sniffed dung deposits for a longer time compared to non-dung objects.

 

While they were sniffing, horses moved their heads across the dung deposits. They showed no specific nostril or ear preference when investigating the target and they tended to blink as they disengaged from sniffing.

 

Horses showed a reduced likelihood of approaching and shorter sniff durations when revisiting dung deposits encountered earlier the same day, regardless of the location. The researchers suggest that this indicates a strong short-term memory for dung and its location.

 

However, horses showed poor memory for dung visited on the previous day, suggesting that their memory for dung is good on the same day but significantly diminishes by the next day. This pattern reflects adaptive forgetting, allowing horses to focus on current environmental cues. (“Adaptive forgetting” refers to the brain's mechanism of intentionally forgetting certain information to optimise memory function and cognitive efficiency. It helps individuals prioritise relevant and important information while discarding outdated, irrelevant, or redundant data. This process is thought to enhance learning, decision-making, and overall cognitive performance.)

 

The researchers suggest that this phenomenon of adaptive forgetting, where memory for dung visited the previous day fades, may be beneficial for horses. It optimizes risk assessment by preventing unnecessary interruptions in foraging caused by conspecifics and ensures that their attention remains focused on current and potentially more relevant environmental cues.

 

 

For more details, see:

 

Audrey EM Guyonnet, Ian Q. Whishaw,

Adaptive forgetting of place/object memory for dung in the domestic horse (Equus ferus caballus): Memory for a day.

Behavioural Processes,

Volume 217,

2024,

105025,

ISSN 0376-6357,

https://doi.org/10.1016/j.beproc.2024.105025

Do endocrine disorders affect anthelmintic performance?

Recent research indicates that insulin dysregulation may affect the performance of anthelmintics
like ivermectin. This suggests that horses with such endocrine disorders might be more prone to parasitic infections.

In a study conducted by Martin Nielsen and colleagues at the University of Kentucky, the response to ivermectin was evaluated in horses with insulin dysregulation (ID), pituitary pars intermedia dysfunction (PPID), or neither condition. 

 

The study population was part of a special herd at the University of Kentucky’s Department of Veterinary Science, which included horses with and without these endocrine disorders. These horses were kept in permanent paddocks without pasture rotation or enhanced hygiene practices and received routine anthelmintic treatments: ivermectin in March or April and July or August, and moxidectin/praziquantel in November.

 

The study focused on senior horses (aged 13 years and over) and those with or without PPID, ID, or both. Out of 47 horses in the research herd, 19 met the criteria for inclusion. These horses, all with positive faecal worm egg counts, were treated with ivermectin at the recommended dose of 200 mcg/kg. Faecal samples were collected before treatment, two weeks post-treatment (for the Faecal Egg Count Reduction Test, or FECRT), and then weekly until worm eggs reappeared in the faeces (Egg Reappearance Period, or ERP).

 

Two laboratory tests were employed to assess the response to ivermectin: the Faecal Egg Count Reduction Test (FECRT) and the Egg Reappearance Period (ERP). For the FECRT, a reduction of at least 99.7% in worm egg counts is considered effective two weeks post-treatment. The ERP for ivermectin is typically 8-10 weeks.

 

The study found no significant differences in the effectiveness of ivermectin between the groups. However, the small sample size may have made it difficult to detect any potential differences. Overall, ivermectin was highly effective, with all horses showing a greater than 99.7% reduction in worm egg counts at the two-week mark. 

 

Nonetheless, the researchers observed that the ERP was shorter in horses with ID and those with both PPID and ID, at six and seven weeks respectively, compared to eight weeks for both the PPID-only and healthy control groups.

 

They suggest that their findings indicate a need for further investigation of the possible influence of endocrine disorders on anthelmintic performance in horses.

 

 

For more details, see:

 

M.K. Nielsen, C.A. Finnerty, N.E. Ripley, A.E. Page, M.E. McClendon, A.A. Adams,

Ivermectin performance in horses diagnosed with equine endocrine disorders,

Veterinary Parasitology, (2024) Vol 328,110182,

https://doi.org/10.1016/j.vetpar.2024.110182

Effect of diet on strongyle infection and gut microbiome

Recent research from France suggests that the first step in controlling intestinal worm infections inanimals should be providing them with diets that maintain a healthy gut ecosystem. 

Horses’ intestines can harbour many different worms, some of which can cause severe disease. It's concerning that some of these worms are becoming resistant to deworming medications. This resistance has emerged through factors such as incorrect dosing or frequent use of the same medications.

 

It's clear that we need to adopt a more sustainable approach to managing equine  intestinal parasites.

 

To address this challenge, scientists are exploring different methods, including dietary changes. These diets might enhance the body's defences, regulate gut bacteria, or directly combat parasites. For example, certain foods containing plant compounds might hinder worm reproduction in the body.

 

A study by Noémie Laroche and colleagues, at Lab to Field, Dijon, and the University of Bourgogne Franche-Comté, investigated how diet affects strongyle infection in horses, focusing on immune-mediated, microbiota-mediated, or direct deworming mechanisms. The work is reported in PLos ONE.

 

They studied twelve adult French Trotter geldings naturally infected with strongyles. These horses were divided into two groups and fed either a high-fibre or high-starch diet, along with supplements containing polyphenol-rich pellets from dehydrated sainfoin or control pellets made from sunflower and hay.

 

The study revealed that horses on a high-starch diet had higher strongyle egg excretion compared to those on a high-fibre diet. However, adding sainfoin to the high-starch diet reduced egg excretion. What’s more, sainfoin supplementation decreased larval motility, regardless of the diet.

 

Moreover, the high-starch diet was associated with lower faecal bacterial diversity, changes in faecal microbiota structure, lower faecal pH, reduced blood acetate levels, and lower haematocrit compared to the high-fibre diet.

 

Overall, these findings suggest that dietary changes can be an alternative strategy for managing helminth infections. 

 

The study highlights the importance of considering broader ecological mechanisms in parasite management strategies. The researchers emphasize that eradicating helminth infections entirely is unrealistic and could have negative effects. 

 

They write: “… pursuing a goal of eradicating helminth infection (zero infection) is not only illusionary but also likely to produce more negative effects than benefits. Mammals have coevolved with helminths during millions of years, and in most cases, the infection does not produce severe symptoms.’

 

“We therefore suggest that a safer strategy to control helminth infection would be to improve host tolerance to the infection rather than pursuing a hopeless, environmentally toxic, strategy of drug-based eradication.”

 

For more details, see:

 

Laroche N, Grimm P, Julliand S, Sorci G (2024) 

Diet modulates strongyle infection and microbiota in the large intestine of horses. PLoS ONE 19(4): e0301920. 

https://doi.org/10.1371/journal.pone.0301920