How the gut-brain connection affects the performance of horses

Diligence is the mother of good luck. –Benjamin Franklin

Article by Scott Anderson

Trainers are always looking to gain an edge in performance. At a minimum, they make sure their athletes get proper nutrition and exercise. Horses require muscle and stamina to compete, so they need to be in top physical condition. But what about their mental state? Are they jittery, distracted or disinterested? No matter how strong the horses are, their heads must be in the game to succeed.

Surprisingly, much of that mental attitude is driven by gut health, which in turn depends on the collection of microbes that live there, called the microbiota. In a horse, the microbiota is a tightly packed community of about 100 trillion microbes, composed of bacteria, archaea, fungi and protozoa. It colonizes the entire GI tract but is largely concentrated in the hindgut, where it works to ferment the prebiotic fiber in forage. The microbial fermentation of fiber into fatty acids produces 70% of the animal’s energy requirements and without it, the horse couldn’t get sufficient energy from simple forage. Intriguingly, byproducts of that fermentation can affect the brain. 

It is easy to be skeptical about this gut-brain connection, but over the last decade, research has made it clear that gut microbes have an outsized influence on mood and behavior. Microbes that improve mental state are called psychobiotics, and they may completely change the way you train and manage your horses. A horse’s health – and consequently its performance – starts in the gut.

Inflammation

When the microbiota is unbalanced by stress, diet or sickness, it is said to be dysbiotic. It loses diversity, and a handful of bacterial species compete for domination. Without the pushback of a diverse population, even beneficial bacteria can become pathogenic. Surprisingly, that can affect the brain. Multiple studies in various animal models have shown that transmitting fecal matter from one animal to another also transmits their mood. This demonstrates that a dysbiotic microbiota can reliably cause mental issues including anxiety and depression, thereby affecting performance. 

An important function of the microbiota is to fight off pathogens by outcompeting, starving or killing them. However, a dysbiotic microbiota is less diligent and may permit pathogens to damage the gut lining. A degraded gut lining can leak, allowing bacteria and toxins into the bloodstream. The heart then unwittingly pumps them to every organ in the body, including the brain. This makes the gut the primary source of infection in the body, which explains why 80% of the immune system is located around the intestines. Over time, a leaky gut can lead to chronic systemic inflammation, which weakens the blood-brain barrier and interferes with memory, cognition and mood. 

Inflammation is a major component of the gut-brain connection, but not the only one.

Neurotransmitters and hormones

Horses and humans use neurotransmitters to communicate between nerve cells. Brains and their attendant nerve bundles constitute a sophisticated network, which makes it somewhat alarming that microbes also produce neurotransmitters. Microbes use neurotransmitters to converse with each other, but also to converse with their host. The entire gut is enmeshed in nerve cells that are gathered up into the vagus nerve that travels to the brain. Microbial neurotransmitters including serotonin and dopamine thus allow certain microbes to communicate directly with the brain via the vagus nerve. We know this happens with specific bacteria, including Lactobacillus species, because when the vagus is severed, their psychobiotic effects disappear. 

As well as neurotransmitters, hormones are involved in gut-brain communications. The hypothalamus-pituitary-adrenal (HPA) axis controls the stress response in animals. The hypothalamus is located low in the brain and responds to stressors – such as a lurking predator – by producing hormones that stimulate the neighboring pituitary, which then triggers the adrenal gland to produce cortisol, the stress hormone. Cortisol acts as a threat warning and causes the horse to ramp up glucose production, supplying the energy needed to escape a predator. This is the same hormonal circuit that trainers exploit for racing.

The HPA axis produces cortisol in response to stress. Cortisol inhibits the immune system, which in combination with a leaky gut allows pathogens to enter the bloodstream. Subsequent systemic inflammation and vagal feedback lead to stereotypies.

The production of these hormones redirects energy to the heart, lungs and muscles at the expense of the immune system. From an evolutionary point of view, the tradeoff makes sense: first escape the predator and deal with infections later. After the danger has passed, cortisol causes the HPA to return to normal – the calm after the storm. 

However, continued stress disrupts that cycle, causing anxiety and diminishing the brain’s ability to store memories. This can dramatically interfere with training. Stress can also induce the release of norepinephrine, which promotes the growth of pathogenic bacteria including Campylobacter jejuni, Listeria, Helicobacter pylori and Salmonella. Prolonged high cortisol levels can increase gut leakiness, potentially leading to infection and further compounding the situation. In the long term, continued stress leads to systemic inflammation, which is a precursor to problematic behaviors.

Short-chain fatty acids

When microbes consume proteins and fiber, they break them down into their constituent molecules, such as amino acids, fatty acids and sugars. These are the metabolites of the microbes. As well as neurotransmitters and hormones, the gut-brain conversation is mediated by metabolites like butyrate  – an important short-chain fatty acid that plays multiple roles in the body. 

In the gut, butyrate serves as a preferred nutrient for the cell lining. It encourages the differentiation of stem cells to replenish gut cells that are routinely sloughed off or damaged. It plays an important role in the production of mucus – an essential part of gut protection – which coats the gut from mouth to anus. In the muscles, butyrate boosts the growth of skeletal muscle, which is crucial to athletic performance, as well as for inducing the production of glucose  – the primary muscle fuel. One-quarter of systemic glucose is driven by butyrate. In its gut-brain role, butyrate passes through the blood-brain barrier, where it nourishes and enhances the growth of new brain cells. 

These factors make butyrate a star player in the gut-brain connection. They also highlight the benefits of prebiotic fiber, especially when high-energy, low-fiber feeds are provided.

Starting a microbiota

We’ve explored the major pathways of the gut-brain connection: inflammation, neurotransmitters, hormones and fatty acids. Some of these pathways are at odds with each other. How does such a complicated system come together?

As mentioned, the microbiota is an animal’s first line of defense against pathogens, attacking and killing them, often before the immune system is even aware of them. That means a healthy microbiota is an essential part of the immune system. However, the immune system is designed to attack foreign cells, which includes bacteria. For the microbiota to survive, the immune system must therefore learn to accept beneficial microbes. This lesson in tolerance needs to take place early in the foal’s development, or its immune system may forever fight its microbiota.

There are multiple ways nature ensures that foals get a good start on a microbiota that can peacefully coexist with the immune system. The first contribution to a protective microbiota comes from vaginal secretions that coat the foal during birth. After birth, microbes are included in the mare’s milk. These microbes are specially curated from the mare’s gut and transported to the milk glands by the lymphatic system. The mare’s milk also includes immune factors including immunoglobulins that help the foal to distinguish between microbial friends and foes. An additional way to enhance the microbiota is through coprophagia, the consumption of manure. Far from an aberration, foals eat their mother’s manure to buttress their microbiota. 

Microbes affect the growth and shape of neurons in various brain sites as the foal develops, a remarkable illustration of the importance of a healthy early gut microbiota. 

The cooperation between the immune system and the microbiota is inevitably complex. Certain commensal bacteria, including Clostridiales and Verrucomicrobia, may be able to pacify the immune system, thus inhibiting inflammation. This is a case where microbes manage the immune system, not the other way around. These convoluted immune-microbial interactions affect the mental state – and consequently the behavior – of the horse, starting at birth.

Stereotypies

A 2020 study of 185 performance horses conducted by French researchers Léa Lansade and Núria Mach found that the microbiota, via the gut-brain connection, is more important to performance than genetics. They found that microbial differences contributed significantly to behavioral traits, both good and bad. A diversified and resilient microbiota can help horses better handle stressors including stalling, training and trailering. A weakened or dysbiotic microbiota contributes to bad behaviors (stereotypies) and poor performance. 

The horses in this study were all carefully managed performance horses, yet the rates of stereotypies were surprisingly high. A kind of anxiety called hypervigilance was observed in three-quarters of the horses, and almost half displayed aggressive behavior like kicking or biting. The study found that oral stereotypies like biting and cribbing were positively correlated with Acinetobacter and Solibacillus bacteria and negatively correlated with Cellulosilyticum and Terrisporobacter. Aggressive behavior was positively correlated with Pseudomonas and negatively correlated with Anaeroplasma. 

Some of these behaviors can be corrected by certain Lactobacillus and Bacteroides species, making them psychobiotics. That these personality traits are correlated to gut microbes is truly remarkable. 

Intriguingly, the breed of a horse has very little impact on the makeup of its microbiota. Instead, the main contributor to the composition of the microbiota is diet. Feeding and supplements are thus key drivers of the horse’s mental state and performance. 

The gut-brain connection and training

How might the gut-brain connection affect your training practices? Here are some of the unexpected areas where the gut affects the brain and vice-versa:

High-energy feed. Horses evolved to subside on low-energy, high-fiber forage and thus have the appropriate gut microbes to deal with it. A high-energy diet is absorbed quickly in the gut and can lead to a bloom in lactic acid-producing bacteria that can negatively impact the colonic microbiota. High-energy feeds are designed to improve athletic output, but over time, too much grain can make a horse antisocial, anxious and easily spooked. This can damage performance  – the very thing it is trying to enhance. Supplementary prebiotics may help to rebalance the microbiota on a high-starch regimen.

Changing feed regimens quickly. When you change feed, certain microbes will benefit and others will suffer. If you do this too quickly, the microbiota can become unbalanced or dysbiotic. Introducing new feeds slowly helps to prevent overgrowth and allows a balanced collection of microbes to acclimate to a new regimen. 

Stress. Training, trailering and racing all contribute to stress in the horse. A balanced microbiota is resilient and can tolerate moderate amounts of stress. However, excessive stress can lead, via the HPA axis, to a leaky gut. Over time, it can result in systemic inflammation, stereotypies and poor performance.

Overuse of antibiotics. Antibiotics are lifesavers but are not without side effects. Oral antibiotics can kill beneficial gut microbes. This can lead to diarrhea, adversely affecting performance. The effects of antibiotics on the microbiota can last for weeks and may contribute to depression and anxiety. 

Exercise and training. Exercise has a beneficial effect on the gut microbiota, up to a point. But too much exercise can promote gut permeability and inflammation, partly due to a lack of blood flow to the gut and consequent leakiness of the intestinal lining. Thus, overtraining can lead to depression and reduced performance.

Knowing how training affects the gut and how the gut affects the brain can improve outcomes. With a proper diet, including sufficient prebiotic fiber to optimize microbiota health, a poor doer can be turned into a model athlete. 

References

Mach, Núria, Alice Ruet, Allison Clark, David Bars-Cortina, Yuliaxis Ramayo-Caldas, Elisa Crisci, Samuel Pennarun, et al. “Priming for Welfare: Gut Microbiota Is Associated with Equitation Conditions and Behavior in Horse Athletes.” Scientific Reports 10, no. 1 (May 20, 2020): 8311.

Bulmer, Louise S., Jo-Anne Murray, Neil M. Burns, Anna Garber, Francoise Wemelsfelder, Neil R. McEwan, and Peter M. Hastie. “High-Starch Diets Alter Equine Faecal Microbiota and Increase Behavioural Reactivity.” Scientific Reports 9, no. 1 (December 9, 2019): 18621. https://doi.org/10.1038/s41598-019-54039-8.

Lindenberg, F., L. Krych, W. Kot, J. Fielden, H. Frøkiær, G. van Galen, D. S. Nielsen, and A. K. Hansen. “Development of the Equine Gut Microbiota.” Scientific Reports 9, no. 1 (October 8, 2019): 14427.

Lindenberg, F., L. Krych, J. Fielden, W. Kot, H. Frøkiær, G. van Galen, D. S. Nielsen, and A. K. Hansen. “Expression of Immune Regulatory Genes Correlate with the Abundance of Specific Clostridiales and Verrucomicrobia Species in the Equine Ileum and Cecum.” Scientific Reports 9, no. 1 (September 3, 2019): 12674. 

Daniels, S. P., J. Leng, J. R. Swann, and C. J. Proudman. “Bugs and Drugs: A Systems Biology Approach to Characterising the Effect of Moxidectin on the Horse’s Faecal Microbiome.” Animal Microbiome 2, no. 1 (October 14, 2020): 38.

Does Jockey Gender Make a Difference?

Experts from the University of Nottingham have found that the sex of a jockey doesn’t influence any aspect of racehorse physiology and performance.

Article by Charlotte Schrurs and David S. Gardner

Charlotte Schrurs

The findings of the study, presently published as a preprint at Research Square, offer a new perspective on the possible balance of elite male and female jockeys on the start line of races.

Studies assessing the effect of the sex of a rider on racehorse performance and physiology during training have not been reported, mostly due to the lack of available data for female participants within the sport.

David S. Gardner

The racing of Thoroughbred horses has a tradition dating back to the 18th century in the UK. However, it was not until the mid-late 20th century that the first ladies’ race was held. In the present day, more than 90% of participating jockeys, in most racing nations, are men. This is likely an unconscious bias toward male jockeys being, on average, physically “stronger,” able to push horses harder, and thus performing better in races than female jockeys.

In horse racing, male and female jockeys compete against each other in the majority of races. This is because the competitive advantage is less on the physical attributes of the rider but more on skill level or ability to partner with an animal. Indeed, racing requires quick reaction time and agility from the jockey while being able to navigate the horse with dexterity across the peloton at peak speeds often exceeding 37mph. This decade has seen a marked increase in participation of female jockeys at an elite level in the racing industry. In 2021, the Irish jockey — Rachael Blackmore — made history by winning several high-profile races. This year, she continued her remarkable rise by becoming the first female jockey ever to win the Gold Cup at the Cheltenham Festival.

Success stories like this are shaping global betting behaviors on the racetrack and challenging the public’s confidence in the ability of male or female jockeys to win big races. In the UK and Ireland, previous research had suggested an underestimation of the ability of female jockeys to win races, as recorded in betting behavior.

In racing, a competitive advantage may lie in the ability of a jockey to control the horse, and/or less weight carried by the horse (i.e. weight of jockey plus saddle). Experts from the University of Nottingham have found that the sex of a jockey doesn’t influence any aspect of racehorse physiology and performance.

Researchers from the School of Veterinary Medicine and Science at the University of Nottingham (UK) worked with Scientific Director Guillaume Dubois, PhD, at Arioneo Ltd — a company that developed a bespoke exercise tracking device for horses; and an Equine Sports Medicine specialist (Dr. Emmanuelle van Erck-Westergren, PhD; Equine Sports Medicine Practice, Belgium) to answer some of these questions.

They monitored 530 Thoroughbred racehorses, ridden by 103 different work riders, which were randomly allocated to a horse (66 male, 37 female) over a total of 3,568 workouts (varying intensity from slow/med/hard canter to gallop) at a single racing yard (with varying tracks – all weather, dirt and turf ) (Ciaron Maher racing) in Victoria, Australia. Variables such as speed, stride length and frequency, heart rate and rate of recovery were recorded with a validated fitness tracker (the ‘Equimetre©’). This tracker was specifically designed to monitor horses during their daily exercise routine with advanced data analysis services (www.arioneo.com).

An average racehorse weighs ~1,100-1,300lbs, an average jockey, ~108-121lbs. Yet, a few ounces extra on the back of a racehorse has been shown to influence race performance. Therefore, weight carried by the horse (jockey, plus saddle and added weights where necessary) is used to further equalize any perceived performance advantage. This allows horses of varying levels to participate in so called “handicap” races. In such races, each horse is attributed a predetermined weight to carry determined by the racing regulatory board.

Horses with better racing records are allocated higher weights in order to further equalize any perceived performance advantage. Hence, jockeys are weighed in before and weighed out after races.

All being equal, would a racehorse during race-pace workouts perform any differently when ridden by either a female or male jockey? Would that racehorse be more or less likely to win a race?

The research monitored 530 Thoroughbred racehorses, ridden by 103 different work riders, which were randomly allocated to a horse (66 male, 37 female) over a total of 3,568 workouts.

WHAT IT IS COMPUTED TOMOGRAPHY?

Computed tomography (CT) helps veterinarians make diagnoses and trainers make decisions. CT scanners take hundreds of x-ray images rotating around the target and create an exact 3D digital rendering. The diagnostic power is in the ability to scroll through the 3D rendering slice by slice, at any angle you choose.

What can it do?

• Small stuff: Tiny P1 fractures and early condylar and coffin fractures: scrolling slices one at a time the tiniest cracks, even bone sclerosis patterns that precede cracks, become clearly visible.

• Hard to see spots: Small bones of the knees and hocks, the suspensory origin, non-displaced cracks in the sesamoids: difficult to evaluate properly on radiographs but clear on CT. CT is also far superior for finding and correcting abnormalities of the skull, teeth and sinuses.

• Cartilage: Arthroscopic surgery has typically been required but by injecting the joint with radio-opaque contrast (sometimes called “dye”) we can see cartilage lesions on CT.

• Fracture prognosis: Two simple condylar fractures may have vastly different outcomes based on trauma unnoticed on plain radiographs. CT enables more accurate prognostication critical for planning the horse’s future.

• The neck: It is shocking how many abnormalities are visible with 3-dimensional imaging of the neck. Nerve compression is visible even when it comes from the side; previously undiagnosable with regular radiographs.

• Surgery: CT guidance enables accurate fracture reconstruction and precise placement of screws in difficult locations.

When to use it?

Think of CT as a microscope; use it when you know where the problem is, but you just can’t see it on radiographs. If you cannot localize the issue, you probably need a bone scan (scintigraphy).

What sets the Mid-Atlantic Equine CT scanner apart?

Image quality and a standing horse.

Two main types of CT: cone beam (x-ray beam is a cone, producing image distortion) and fan beam (beam is a thin blade).

Image detail is far superior with fan beam; the main reason Mid- Atlantic Equine moved to it from the robotic CT. Most fan beam CT units are small and require general anesthesia. The CT scanner at Mid-Atlantic Equine is a Canon large bore CT mounted on a computer controlled platform, allowing true CT imaging in a standing horse (foot to forearm or gaskin, nose to base of the neck C5/6 or 6/7). Under anesthesia imaging of elbows, shoulders, chest, thoracic spine, back, pelvis, SI, hips and stifles can be obtained. Medical care so advanced it almost makes you wish you were a horse. We offer every type of medical care your four-legged athlete could ever need. With board-certified specialists in all fields we provide everything from upper airway, arthroscopic and laparoscopic surgeries, to internal medicine, complex fracture fixation and advanced diagnostic imaging, including bone scans and MRIs — all in one place.

It’s enough to make a human jealous.

Contact:

Tel. 800.724.5358 Address: 40 Frontage Road Ringoes, NJ 08551

Web: www.midatlanticequine.com

The Often Overlooked Equine Sacroiliac Joint

Horses that present as sore in the hindquarters can be perplexing to diagnose. Sometimes the problem is found in the last place you look – the sacroiliac joint.

Article by Annie Lambert

Even though the sacroiliac joint (SI) was on veterinary radars long ago, due to its location buried under layers of muscle in the equine pelvic region, the joint and surrounding ligaments were tough to diagnose and treat.

The sacroiliac joint is often a source of lower back discomfort in race and performance horses. Trainers may notice several clinical signs of a problem. These hints include sensitivity to grooming, objections to riders getting legged up, stiffness of motion, pain to manual palpation of the rump or back, resistance to being shod behind and poor performance.

Of course, those symptoms could describe other hind limb soundness issues, making the origin of the problem arduous to ascertain. A thorough physical examination with complete therapeutic options can relieve sacroiliac pain. The treatments are complicated, however, by the anatomy of the SI area. 

The equine pelvis is composed of three fused bones: ilium, ischium and pubis. The sacrum, the lower part of the equine back, is composed of five fused vertebrae. The sacroiliac joint is located where the sacrum passes under the top of the pelvis (tubera sacrale). The dorsal, ventral and interosseous sacroiliac ligaments help strengthen the SI joint. 

The SI and surrounding ligaments provide support during weight bearing, helping to transfer propulsive forces of the hind limbs to the vertebral column—creating motion much like the thrust needed to break from the starting gate.

Sound complicated? It certainly can be.

Diagnosing Dilemmas

It wasn’t until modern medical technology advanced that the SI could be explored seriously as a cause of hind lameness.

“The sacroiliac is one of the areas that’s very hard to diagnose or image,” explained Dr. Michael Manno, a senior partner of San Dieguito Equine Group in San Marcos, California. “[Diagnostics] of the area probably correlated with bone scans or nuclear scintigraphy. You can’t really use radiographs because the horse is so massive and there is so much muscle, you can’t get a good image.

“About the only time you can focus on the pelvis and get a decent radiograph is if the horse is anesthetized—you have a big [x-ray] machine and could lay the horse down. But, it’s hard because with anything close to a pelvic injury, the last thing you want to do is lay them down and have them have to get back up.”  

The nuclear scintigraphs give a good image of hip, pelvis and other anatomical structures buried deep in the equine body, according to Manno, a racetrack practitioner. “Those images can show areas of inflammation that could pretty much be linked right to the SI joint.”

The other modern technological workhorse in the veterinary toolbox is the digital ultrasound machine. Manno pointed out that veterinarians improved diagnostics as they improved their ultrasounding skills and used those skills to ultrasound areas of the body they never thought about before. Using different techniques, frequencies and various heads on the machine’s probe, the results can be fairly remarkable.

“The ultrasound showed you could really image deeper areas of the body, including an image of the sacroiliac joint,” Manno said. “It can also show some ligament issues.”

Where the SI is buried under the highest point of a horse’s rump, and under heavy gluteal muscles, there are two sets of ligaments that may sustain damage and cause pain. The dorsal sacroiliac ligaments do not affect the sacroiliac joint directly, but help secure the ilium to the sacral spine. The ventral sacroiliac ligaments lie deeper, in the sacroiliac joint area, which they help stabilize. These hold the pelvis tight against its spine. The joint itself, being well secured by these ligaments, has little independent movement and therefore contains only minimal joint fluid.

Diagnosing the SI can be complex because horses often travel their normal gait with no change from normal motion—no signs of soreness. Other horses, however, are sore on one leg or another to varying degrees, sometimes with a perceptible limp. 

“I don’t know that there is a specific motion,” Manno explained. “You just know that you have a hind end lameness, and I think a lot of performance horses have mildly affected SI joints. 

“The horses that are really severe become acutely lame behind, very distinct. You go through the basic diagnostics, and I think most of these horses will show you similar signs as other issues behind. We palpate along the muscles on either side of their spine and they are sore, or you palpate over their croup and you can get them to drop down—that kind of thing. Other times you do an upper limb flexion on them and they might travel weird on the opposite leg. So, it can be a little confusing.” 

In the years prior to the early 2000s, the anatomical location of the SI hindered a definite diagnosis; decisions on hind soreness were more of a shrug, “time and rest” treatment evaluation. As one old-time practitioner called it, a SWAG – “Scientific Wild Ass Guess.”

Even with modern tools, making a conclusive diagnosis can be opaque.

“The less affected horses, through exercise and with medications like Robaxin [muscle relaxer] or mild anti-inflammatories, seem to be able to continue to perform,” Manno said. “I don’t know how you can be perfectly sure of an inside joint unless you try to treat it and get results.”

“That’s why bone scans came into play and are really helpful,” Manno added. “You can image that [SI] area from different angles with the machine right over the path of the pelvis, looking down on it or an angle view into it, and then you see it from the side and the back very often. We can get an idea from the different views and angles of where the inflammation is and pinpoint the problem from that.” 

Once Manno has a generalized idea of where the problem is, he fine-tunes his hypothesis using more diagnostics with a digital ultrasound machine. 

“You can ultrasound from up above and see the joint that way,” he said. “As ultrasound has progressed, we’ve found that the rectal probes the breeding vets have used can also be tuned in to start looking for other things. If you turn them upwards, you can look at the bottom of the pelvis and the SI joint. You can see things through the rectum by just looking straight up. That is a whole new thing that we probably never thought about doing. I don’t profess to be very great at it; it’s not something I do a lot, but there are people that are just wonderful at it.” 

Treating a Theorem

But, if the diagnosis is incorrect, the prescribed treatment may be anything but helpful.

“In many cases, if a horse is really sore, you need to be very careful,” cautioned Manno. “What you don’t want to do is go from a strain or some sort of soft tissue injury into a pelvic fracture by trying to keep them going. In many cases you are back in the old rest and time type of treatment.”

Manno pointed out one treatment that has advanced over many years is injecting the SI joint directly. There are a couple of techniques used when injecting the SI. With a blind injection the practitioner directs a long, straight needle into the joint by relying solely on equine anatomy. The other technique employs an ultrasound machine to guide the placement of the needle into the joint.

“Normally we are just injecting cortisone in those cases,” Manno noted. “We are trying to get the inflammatory response to settle down. Hopefully that gives the horse some relief so that they’re a bit more relaxed in their musculature. You know how it is when you get a sore back; it’s hard to keep yourself from cramping, which makes everything worse.”

A slight tweak of that technique is to use a curved needle. When you are positioning the curved needle, it follows the curve of the horse’s anatomy and helps the practitioner direct the injection into the joint.

“It curves right into position for you; it gives you a little help,” Manno confirmed of the curved needle. “Some people are really good with that technique; others still like to go to the straight needle. [The curved needle] helps you approach the site without interference from the bones in that area.”

SI joint injuries affect most performance horses, including Standardbred trotters and pacers, Western performance athletes as well as hunters, jumpers and dressage horses.

The older show horses are often diagnosed with chronic SI pain, sometimes complicated by arthritis. These chronic cases—and admittedly some racehorses—are treated with different therapies. These conservative, nonsurgical treatments have been proven effective.

In addition to stall rest and anti-inflammatories, physical training programs can be useful in tightening the equine patient’s core and developing the topline muscles toward warding off SI pain. Manno, a polo player who also treats polo ponies, believes the hard-working ponies avoid having many SI injuries due to their fitness levels. 

“I think these polo horses are similar to a cross between a racehorse and a cutting horse,” Manno opined. “They are running distances and slide stopping and turning.”

Other treatments utilized include shockwave, chiropractic, acupuncture, therapeutic laser and pulsed electromagnetic therapy.

Superior Science

With the new diagnostic tools and advanced protocols in their use, veterinarians can pinpoint the SI joint and surrounding areas much closer. This gives them an improved indication that there definitely is an issue with the sacroiliac. 

When there is a question about what is causing hind end lameness, most practitioners begin with blocking from the ground up.

“In many cases with hind end lameness that we can’t figure out, we block the lower leg; if it doesn’t block out down low, we conclude the problem is up high,” Manno said. “Once you get up to the hock you’re out of options of what you can figure out. You start shooting some x-rays, but by the time you get to the stifle, you’re limited. Bone scans and ultrasounds have certainly helped us with diagnosing.”

Manno doesn’t see a lot of SI joint injuries in his practice, but he noted there were cases every now and again. He also opined that there were probably other cases that come up in racehorses on a short-term basis. He also noted that, although it may not be a real prominent injury, that’s not to say it has not gone undiagnosed.

“I think we realize, in many of the horses we treat, that the SI joint is something that may have been overlooked in the past,” Manno concluded. “We just didn’t have the ability to get any firm diagnosis in that area.”

Modern Saddle Design - how technology can quantify the impact saddles have on performance

By Dr. Russell Mackechnie-Guire

Thanks to advances in technology, it is getting easier for scientists to study horses in a training environment. This, combined with recent saddlery developments in other disciplines, is leading to significant progress in the design and fit of exercise saddles.

Back pain, muscle tension and atrophy are common issues in yards. Although there are many contributory factors, the saddle is often blamed as a potential cause. Unlike other equestrian sports, where the effect of tack and equipment on the horse has been investigated, until now there has been little evidence quantifying the influence of exercise saddles.

New era

The technological advances used in sport horse research are sparking a new era in racing, enhancing our understanding of the physiological and biomechanical demands on the horse, and helping improve longevity and welfare. For the trainer this translates into evidence-based knowledge that will result in marginal or, in some cases, major gains in terms of a horse’s ability to race and achieve results. Race research has always been problematic, not least due to the speed at which the horse travels. Studies have previously been carried out in gait laboratories on treadmills, but this is not representative of normal terrain or movement. Thanks to new measuring techniques, we can now study the horse in motion on the gallops. Evidence of this new era arises from a recent study published in the Journal of Equine Veterinary Science. It found areas of high pressures under commonly used exercise saddles which had a negative influence on back function, affecting the horse’s gallop and consequently performance. 

The pressure’s on

Researchers used a combination of pressure mapping and gait analysis (see Technology in focus panel) to investigate three designs of commonly used exercise saddles: full tree, half tree and three-quarter tree. The aim was to identify pressure magnitude and distribution under each of the saddles then to establish whether the gait (gallop) was improved in a fourth saddle designed to remove these pressures. 

Areas of high pressure were found in the region of the 10th-13th thoracic vertebrae (T10-T13). Contrary to popular belief, none of the race exercise saddles tested in this study produced peak pressure on or around the scapula. The pressures around T10-T13 at gallop in the half, three-quarter and full tree were in excess of those detected during jumping or dressage in sport horses. They were also higher than pressures reported to be associated with clinical signs of back pain. Therefore, it is widely accepted that high pressures caused by the saddle could be a contributory factor to back pain in horses in training.  

Three most commonly used saddle-tree lengths, plus the new design (purple 40cm)

Half tree: High peak pressures in the region of T10-T14 were consistent with the end of the tree.

Three-quarter tree: Peak pressure was localised on one side of the back at a time, depending on the horse’s gallop lead.

Full tree: Peak pressure was further back and, although not high, gait analysis demonstrated a reduction in the extent to which the hindlimb comes under the horse, reducing the power in the stride.

New design: A more uniform pressure distribution, recording the lowest peak pressures at each location.

Lower pressure leads to longer strides

When looking at propulsion, there are two important measurements: the angle of the femur relative to the vertical and hip flexion. When pressures were reduced beneath the saddle, researchers saw an increased femur-to-vertical angle in the hindlimb and a smaller hip flexion angle (denoting the hip is more flexed).

A greater femur-to-vertical angle indicates that the hindlimb is being brought forward more as the horse gallops.

A smaller hip flexion angle denotes the hip is more flexed, allowing the horse to bring his quarters further under him and generate increased power.

mproved hip flexion was recorded in the new saddle design (A) compared to a commonly used saddle

When pressure is reduced in the region of T13, the hindlimb is allowed to come more horizontally under the horse at this point in the stride, leading to an increase in stride length. Researchers speculate that this could be due to the fact that the thorax is better able to flex when pressure is reduced.

Perhaps surprisingly, the study found that reducing saddle pressures did not result in any significant alteration in the forelimb at gallop. The major differences were recorded in hindlimb function. This could be explained anatomically; the forelimb is viewed as a passive strut during locomotion, whereas the hindlimbs are responsible for force production.

This is consistent with findings in the sport horse world, where extensive research investigating pressures in the region of the 10th-13th thoracic vertebrae has shown that reducing saddle pressure is associated with improved gait features in both dressage and jumping. 

Speed matters…

CLICK HERE to return to issue contents

ISSUE 57 (PRINT)

$6.95

ISSUE 57 (DIGITAL)

$3.99

WHY NOT SUBSCRIBE?

DON'T MISS OUT AND SUBSCRIBE TO RECEIVE THE NEXT FOUR ISSUES!

Four issue subscription - ONLY $24.95

Modern saddle design - how technology can quantify the impact saddles have on performance

By Dr Russell Mackechnie-Guire

Thanks to advances in technology, it is getting easier for scientists to study horses in a training environment. This, combined with recent saddlery developments in other disciplines, is leading to significant progress in the design and fit of exercise saddles.

Back pain, muscle tension and atrophy are common issues in yards. Although there are many contributory factors, the saddle is often blamed as a potential cause. Unlike other equestrian sports, where the effect of tack and equipment on the horse has been investigated, until now there has been little evidence quantifying the influence of exercise saddles.

New era

The technological advances used in sport horse research are sparking a new era in racing, enhancing our understanding of the physiological and biomechanical demands on the horse and helping improve longevity and welfare. For the trainer this translates into evidence-based knowledge that will result in marginal or, in some cases, major gains in terms of a horse’s ability to race and achieve results. Race research has always been problematic, not least due to the speed at which the horse travels. Studies have previously been carried out in gait laboratories on treadmills, but this is not representative of normal terrain or movement. Thanks to new measuring techniques, we can now study the horse in motion on the gallops. Evidence of this new era arises from a recent study published in the Journal of Equine Veterinary Science. It found areas of high pressures under commonly used exercise saddles which had a negative influence on back function, affecting the horse’s gallop and consequently performance. 

Figure 1: Three most commonly used saddle-tree lengths, plus the new design (purple 40cm)

The pressure’s on

Researchers used a combination of pressure mapping and gait analysis (see Technology in focus panel) to investigate three designs of commonly used exercise saddles: full tree, half tree and three-quarter tree. The aim was to identify pressure magnitude and distribution under each of the saddles then to establish whether the gait (gallop) was improved in a fourth saddle designed to remove these pressures. 

Areas of high pressure were found in the region of the 10th-13th thoracic vertebrae (T10-T13). Contrary to popular belief, none of the race exercise saddles tested in this study produced peak pressure on or around the scapula. The pressures around T10-T13 at gallop in the half, three-quarter and full tree were in excess of those detected during jumping or dressage in sport horses. They were also higher than pressures reported to be associated with clinical signs of back pain. Therefore, it is widely accepted that high pressures caused by the saddle could be a contributory factor to back pain in horses in training.  

FIgure 2: Half tree: High peak pressures in the region of T10-T14 were consistent with the end of the tree.

Three-quarter tree: Peak pressure was localized on one side of the back at a time, depending on the horse’s gallop lead.

Full tree: Peak pressure was further back and, although not high, gait analysis demonstrated a reduction in the extent to which the hindlimb comes under the horse, reducing the power in the stride.

New design: A more uniform pressure distribution, recording the lowest peak pressures at each location.]

Lower pressure leads to longer strides

Figure 3: A greater femur-to-vertical angle indicates that the hindlimb is being brought forward more as the horse gallops.

When looking at propulsion, there are two important measurements: the angle of the femur relative to the vertical and hip flexion. When pressures were reduced beneath the saddle, researchers saw an increased femur-to-vertical angle in the hindlimb and a smaller hip flexion angle (denoting the hip is more flexed).

Figure 4: A smaller hip flexion angle denotes the hip is more flexed, allowing the horse to bring his quarters further under him and generate increased power.]

When pressure is reduced in the region of T13, the hindlimb is allowed to come more horizontally under the horse at this point in the stride, leading to an increase in stride length. Researchers speculate that this could be due to the fact that the thorax is better able to flex when pressure is reduced.

Perhaps surprisingly, the study found that reducing saddle pressures did not result in any significant alteration in the forelimb at gallop. The major differences were recorded in hindlimb function. This could be explained anatomically; the forelimb is viewed as a passive strut during locomotion, whereas the hindlimbs are responsible for force production.

Figure 5: Improved hip flexion was recorded in the new saddle design (A) compared to a commonly used saddle (B).

This is consistent with findings in the sport horse world, where extensive research investigating pressures in the region of the 10th-13th thoracic vertebrae has shown that reducing saddle pressure is associated with improved gait features in both dressage and jumping. 

Speed matters

High speeds are associated with higher vertical forces beneath the saddle. It has been shown that a 10% increase in speed at walk increases pressures under the saddle by 5%, and in trot the figure rises to 14%. Figures for canter or gallop have not been recorded, but pressures under exercise saddles were significantly higher than in dressage or jumping, despite the jockey being in a standing position and having a lower center of mass compared to most other equestrian athletes. Plus, race exercise saddles are lighter than those in other disciplines. These findings support the theory that the higher pressures seen in gallop are due to forces created by an increase in speed.

At walk, with the addition of a rider, the forces on the horse’s back are equivalent to the rider’s body mass. At trot, this becomes equivalent to twice the body mass, and two-and-a-half times at canter. In gallop, the horse’s back is experiencing a higher range of motion than in any other gait; so if the saddle induces high pressures or limits this movement, it will undoubtedly compromise the gallop. The speed in this study was standardized so that any alterations in pressure distribution would be directly attributed to the saddle and not to alterations in ground reaction forces. 

Efficiency of stride

Horses in training spend most of their time in an exercise saddle. As each loading cycle causes joint wear and tear, if a new design of the exercise saddle can help the horse achieve a longer stride length, this would mean fewer strides are necessary to cover any given distance. A study has suggested that horses have a maximum number of gallop strides in them before they fail, so any reduction in stride quantity (loading cycles) could potentially reduce injury risk. 

Compared to work, when racing, the saddle pressures are higher still. A study in 2013 looking at pressures under race saddles identified peak pressures on the spinous processes of the actual vertebrae. These pressure-sensitive bony prominences are not evolved to withstand pressure and are less equipped than the surrounding muscles to do so. Spinal clearance is, therefore, an important consideration.

Pressure pads

All saddles tested in the recent research achieve spinal clearance by means of panels separated by a channel. However, in an attempt to alleviate spinal pressure and make one saddle fit many horses, it’s standard practice to use multiple pads under an exercise saddle. This is counterproductive as it can lead to saddle instability. In galloping race horses, forward or backward slip is an issue, and this could be attributed to the use of pads. In addition, too much bulk under the saddle puts a feeling of distance between the horse and jockey.

Tack and equipment form one part of a multi-factorial approach to training, and it is an area that, until now, has been largely overlooked by the scientific community. ….

BUY THIS ISSUE IN PRINT OR DOWNLOAD

ISSUE 55 (PRINT)

$6.95

ADD TO CART

ISSUE 55 (DIGITAL)

$3.99

ADD TO CART

WHY NOT SUBSCRIBE?

DON'T MISS OUT AND SUBSCRIBE TO RECEIVE THE NEXT FOUR ISSUES!

Four issue subscription - PRINT & ONLINE - ONLY $24.99

ADD TO CART

The concept of Marginal Gains - how it can alter performance

CLICK ON THE IMAGE ABOVE TO READ ONLINE!

Does bleeding affect performance? Results of a ten year study

CLICK ON THE IMAGE ABOVE TO READ ONLINE!