Conference Continues with Roster of Top-Flight Researchers as Speakers

The second day of the 27th Equine Health and Nutrition Conference, hosted by Kentucky Equine Research and held in Ocala, Florida, February 5-6, showcased another roster of top-flight researchers.

First to speak was Dr. Wendy Pearson, associate professor of equine physiology at the University of Guelph, giving back-to-back presentations titled “Role of Inflammation in Adaptations to Exercise Stress” and “Influence of Nutrition in Leaky Gut Syndrome.”

“Inflammation is a normal, transient immune response to trauma or infection. Its purpose is to rid the body of pathogens and damaged tissue, and stimulate the growth of new healthy tissue,” said Pearson.

When asked how to differentiate beneficial inflammation from damaging inflammation, Pearson called that the million-dollar question.

“Because inflammation tends to be associated—rightly or wrongly— with how uncomfortable it makes us (and our horses) feel, it is tempting to treat it as something inherently ‘bad’ that should be avoided whenever and wherever possible,” she explained. “However, the transient inflammation that is realized from exercise is key to the many benefits that are well known to result from regular exercise.”

Pearson addressed leaky gut syndrome in her second presentation. With leaky gut syndrome, inflammation increases the permeability of the gastrointestinal lining, allowing harmful substances to pass from the gastrointestinal tract into the bloodstream.

While leaky gut syndrome is not a current medical diagnosis, according to Pearson, “it is sometimes presumptively diagnosed based on the presence of risk factors and inflammation-related disorders, when other potential causative factors have been ruled out.”

Dr. Mike Davis, professor, the Oxley Endowed Chair in Equine Sports Medicine, and the director of the Comparative Exercise Physiology Laboratory at the Oklahoma State University College of Veterinary Medicine, returned to the podium on Tuesday with his first talk of the day, “The Mighty Mitochondria.”

“There are lots of different ways to study mitochondria, and we are getting better at it. For a very long time, the most common way of studying mitochondria was to simply count them based on quantifying the abundance of key enzymes,” explained Davis. “That is still very common because it is quick and relatively easy. Because the mitochondria are where oxygen ultimately gets burned during metabolism, quantifying oxygen consumption of tissue or cell samples was the most common way of quantifying their function.”

When asked why horse owners and veterinarians would be interested in this research, he said, “We are getting down to the nitty-gritty of what causes fatigue during exercise, which is of interest to anyone who hopes their horse fatigues last in the race. I am trying to nail down exactly what causes a horse to fatigue—to slow down—as more than half of the horses in any given race are doing at the end of the race. The winner is not the fastest horse, it is the horse that slows down the least so, in a way, I am trying to identify what makes a horse a winner.”

Dr. Stephanie Valberg returned to the podium for her second presentation of the conference, titled “Cutting-Edge Technologies for Studying Muscle Metabolism.” Part of her presentation included an introduction to “omic” technologies which, according to her, allow researchers to obtain a comprehensive understanding of biological systems in muscle that was not previously possible.

Examples of “omics” include proteomics, transcriptomics, genomics, metabolomics, lipidomics, and epigenomics, which correspond to global analyses of proteins, RNA, genes, metabolites, lipids, and methylated DNA or modified histone proteins in chromosomes, respectively.

“To date, proteomics, transcriptomics, genomics, and metabolomics have been used by a small number of researchers to study equine skeletal muscle in health and disease. The results of these studies have helped us to capture the myriad of events that can combine to cause muscle dysfunction in horses and recently to study limitations in glycogen repletion in horses.”

Dr. Joe Pagan, founder and president of Kentucky Equine Research, followed Valberg. In his presentation titled “Omega-3 and Omega-6 Fatty Acids in Equine Nutrition,” he presented a brief overview of these important polyunsaturated fatty acids and then described some studies conducted at Kentucky Equine Research that have yielded important results.

“Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are omega-3 fatty acids and generally beneficial. We tend to think that all omega-6s are bad or inflammatory. However, di-homo-gamma-linolenic acid (DGLA) has some anti-inflammatory properties,” explained Pagan.

“We have discovered that if horses are fed gamma-linolenic acid, or GLA, a short-chain omega-6 fatty acid, you can enhance the amount of DGLA. One lipid mediator of DGLA is prostaglandin E1 that, in synthetic form (misoprostol), is used to inhibit gastric acid and enhance mucosal resistance to injury in the stomach.”

Dr. Mike Davis then gave his final presentation of the conference, this one titled “Heat Stress: A Comparative Approach Between Species and Disciplines.” He first described the differences between heat stress, heat injury, and heat stroke, as the terms can become somewhat muddied and cause confusion.

Heat stress is the increase in body temperature that causes any change in physiology that, in attempting to mitigate the increase in body heat, impairs another function. “A great example is a panting dog. That dog is changing its breathing pattern specifically to attenuate an increase in body temperature, but in doing so is impairing its ability to smell,” said Davis. When defined in this manner, heat stress does not cause harm or injury; it is merely an indication that the body has become too hot to do everything, so it is starting to pick and choose, according to Davis.

As its name implies, heat injury indicates that damage has occurred. This could be to muscle, gastrointestinal tract, or other tissues. It does not mean that overt clinical illness has occurred, but something has been damaged and will need repair. Finally, there is heat stroke, which “is used to denote overt clinical illness because the systems have been so injured and so altered that the subject is no longer capable of even normal bodily function,” described Davis.

In his summary, Davis mentioned two essential take-home messages: (1) The best scientific evidence supports rapid cooling of an overheated athlete. There is no such thing as cooling an athlete too fast, although it is possible to cool them too much. If they are demonstrating signs of heat injury, get them to a normal body temperature as quickly as you can, but not lower than normal body temperature, and (2) Water application or immersion is by far the most effective practical means of cooling a hot athlete, and all organized athletic events should have that capacity on-site and available without restriction.

Drs. Sally DeNotta and Samantha Brooks presented the next talk, “Should You Sweat it? Anhidrosis in the Equine Athlete.” DeNotta provided an overview of anhidrosis in horses, including common symptoms and management tips. Brooks described contributions in identifying the genetic basis for anhidrosis.

“To look for heritable factors contributing to anhidrosis, we used a technology that examines markers found evenly across the entire genome of the horse,” Brooks said. “Each of these markers has two different possible types, and tracking these types in each horse gives us a way to distinguish one region of the genome from another.”

Dr. Joe Pagan filled the last two slots of the program with presentations titled, “New Methods for Studying Exercise-Induced Stress in Horses” and “Electrolytes and Hydration.”

Pagan spoke about an exciting new possibility in measuring stress in horses. “An important innovation has come about, and that is the use of microchips that can measure temperature.”

Traditionally, microchips are put in the nuchal ligament in the neck, but recently a research group at the University of Queensland experimented with taking these microchips and placing them in various muscle tissues in the horse.

“Those researchers performed studies to look at how well the temperatures taken by microchips correlated with core body temperature, which they measured by insertion of a catheter deep in the cardiovascular system,” Pagan said. “The researchers implanted these chips into different muscles, one of which is the middle gluteal muscle, a major muscle that overlies the hip of the horse.”

Kentucky Equine Research has recently taken this validated technology and has applied it to 12 Thoroughbreds used in its research program in Florida. “Each of these horses had microchips implanted into its middle gluteal muscle and pectoral muscle. These horses were physically fit, as they had been in training on a high-speed treadmill for several months. We conducted several studies first to see what kind of muscle temperature occurred in response to treadmill exercise. We also looked at how various types of cooling methods affected recovery, muscle temperature, heart rate, and respiratory rate,” Pagan explained.

Because this is a brand-new technology, researchers are in the early days of understanding different cooling methodologies and potential nutritional interventions to aid recovery. “Having the microchip technology available to us is especially encouraging, as this is a repeatable, noninvasive method for accurately measuring recovery from exercised-induced heat stress,” he said.