Osteoarthritis in Horses and the Effects of Supplements
Osteoarthritis in Horses and the Effects of Supplements
The following article recaps the research discovered through a study funded by the American Quarter Horse Foundation. The Foundation fills a vital role by being just one of four private institutions funding research. Make a contribution at www.aqha.com/equine-research.
By Megan Arszman
Each year, horse owners spend thousands of dollars on dietary supplements for their horses for numerous reasons. It’s a multimillion-dollar business. Researchers wonder: Is all this supplementation necessary? If so, when should horse owners feed these supplements?
These questions have been a primary focus for Jessica Leatherwood, an assistant professor in animal science at Texas A&M University, who has been spending years working toward preventing joint disease through modification of exercise protocols as well as nutritional strategies.
Receiving a grant from the American Quarter Horse Foundation has been exactly the boost she needed to start the research into a question that she has spent years thinking about.
“It's actually a full circle effect for me,” Jessica says. “The Foundation funded a scholarship for me to attend Texas A&M as an undergraduate. It has really meant a lot to me, and I appreciate the opportunities that the Association has provided to me, both personally and professionally.”
Jessica has been evaluating a range of ages in which modification and exercise protocols or nutrition will have the greatest impact on joint inflammation and cartilage metabolism. As a student in the master’s and doctoral program at Texas A&M, Jessica worked with Josie Coverdale, who was an associate professor in animal science prior to her untimely death in 2016.
The pair worked together to objectively evaluate joint health in young performance horses. The Foundation provided a grant to help evaluate the response of the equine joint with the use of intra-articular lipopolysaccharide (LPS) injection, specifically relating to inflammation and cartilage metabolism. Osteoarthritis (OA) is a significant cause of lameness in performance horses that often leads to the early retirement of young equine athletes.
Adaptation of bone and soft tissue occurs during early growth and exercise. During this adaptation, young horses undergo repeated trauma and stress that can result in excess production of inflammatory mediators that over time can result in the enzymatic breakdown of articular cartilage. Cartilage can both repair and degrade after trauma, possibly influenced by age-related changes.
“Long yearlings (18 months of age) in training programs that are placed on a rapid plane of upgrowth may be negatively viewed by some owners and breed associations,” Jessica says. “We hope to identify optimal times at which reparative processes for articular cartilage are favored over degenerative breakdown that is relative to the age of the horse. Furthermore, identifying complementary dietary products that could prevent or delay the onset of developing joint disease for performance horses later in life would also be beneficial. The goal of my work is to improve the longevity and use of the performance horse.”
During her master’s studies, Jessica realized that the limitations and subjectivity associated in evaluating on-farm lameness characteristics and working horses under saddle.
“We did our best to evaluate joint health and exercising model: we would rotate riders to account for variation in rider weight and randomly select horses to be equipped with heart rate monitors each day during exercise, but despite our efforts, we were not able to remove inherent variation on articular cartilage due to the exercise,” she explains.
Lipopolysaccharides in Horses
Following her experiences during her master’s degree research, she turned her efforts to finding a way to induce a predictable level of inflammation in the horse, directly into the joint capsule, that was similar to producing a level of inflammation that was seen in naturally occurring osteoarthritis without causing any long term effects to the research horse.
Most research has focused on horses that have been previously diagnosed with lameness, and the study ends with a dissection of the horse.
Jessica had a different plan.
“Typically our research herd is also used as part of our behavior and training courses here at Texas A&M,” she says. “Our goal was to be able to cause a predictable yet transient inflammatory response in a young horse that was free from any clinical signs of lameness. As a responsible researcher, horse care welfare is always our top priority.”
The problem was trying to find a way to conduct the study that would get results but would leave the young horse undamaged.
Jessica found an endotoxin called lipopolysaccharide, or LPS, which is found on the outer leaflet of all gram-negative bacteria.
The LPS is injected in minute volumes into the horse’s joint capsule to cause an inflammatory response that only lasts for 24 hours.
To initially test the gram-negative bacteria, the researchers enlisted Dr. Carolyn Arnold, a veterinarian and assistant professor at Texas A&M in large-animal clinical sciences, for a pilot study with a group of weanlings on the effectiveness of the LPS.
“Dr. Arnold was instrumental in providing her expertise relating to the dosage to be administered and horse sensitivity with her previous experiences while on faculty at Kansas State,” Jessica says. “She has also performed all of the arthrocentesis procedures.”
The goal was to establish appropriate dosages. After initial tests, the trio of researchers determined there were no long-term effects on the weanlings, their No. 1 priority.
“We didn't induce fever or change normal clinical parameters such as heart rates, respiration rates or rectal temperatures, which would indicate a change in their physiological status,” Jessica says. “Even though our parameters remained within normal ranges, the LPS was sensitive enough to cause an increase in intra-articular inflammation in alter cartilage turnover - through the measurement of synovial peptides that are indicative of recent synthesis and degradation.”
Increased Inflammatory Response in Older Horses
The next level of Jessica's studies was meant to see whether the way horses respond to the LPS was different relative to their age – meaning, do young horses and their cartilage markers respond differently than older horses?
“We evaluated the age-related effect on markers of inflammation and cartilage metabolism in response to this particular LPS challenge,” she explains.
Now that researchers knew that using the lipopolysaccharide was safe, they looked at how age was going to affect the horse’s response to the injection.
They used three different groups of horses: yearlings, horses aged 2-3 and horses aged 5-8. Older horses have more pre-existing abnormalities to attenuating joints that could have altered or compounded the results of the study.
During the trial, the horses all received an injection of the LPS in the knee, while the other knee had an injection of LRS (lactated ringer solution), a control to allow for differences or comparisons between the two injections.
From this study, Jessica found that a synovial marker of inflammation was greater in the mature horses when compared to younger horses.
Additionally, a marker of collagen degradation was 1.5 times greater in mature horses compared to both yearlings and 2- and 3-year-olds, which indicates an increase in degradative response in mature horses when exposed to intra-articular LPS.
However, mature horses showed increased ability for articular cartilage repair over young horses, possibly because the amount of degradation in these horses was higher overall. This elevated ability towards re-synthesis in mature horses might also be accomplished by increased damage to matrix molecules shown to be important for the integrity of the joint and its ability to function.
Values for mature horses peaked later than younger horses, possibly indicating the slower turnover rate in mature horses compared to young horses. The study suggests that mature horses might have an increased ability to re-synthesize cartilage in response to inflammation and enzymatic breakdown when compared to younger horses, however the process takes longer and might be accomplished by increased damage to newly synthesized matrix molecules.
Further studies are needed to clarify this relationship between horses of varying ages.
“This particular study provides us with the idea that there is an increased inflammatory response in our older horses in response to an LPS injection,” she says. “Although OA is believed to exist primarily in the aged horse, the disease is thought to result from cartilage damage that may develop when training occurs early in life.”
Results from this study indicate an increasing inflammatory response with age and horses, accompanied by greater amounts of cartilage degradation and repair, and greater amounts of damage in the newly synthesized cartilage.
With age, the rate of cartilage re-synthesis decreases. After a single inflammatory insult, this decreased rate does not appear to limit the ability of the mature horse to repair damaged cartilage, she says.
However, it is possible that without an adequate rest period, the older equine athlete returning to work might not have time to sufficiently complete the cartilage repair process.
“Further studies are needed to confirm the effects of age on inflammation and cartilage metabolism and exercising horses exposed to chronic joint inflammation,” Jessica says.
The Effect of Supplements in Young Performance Horses
For a dietary supplement to be effective, the horse has to consume the product.
That product then has to travel to the gastrointestinal tract and be absorbed across the GI tract into circulation and then be incorporated into active tissue sites such as the articulating cartilage.
“With any supplement on the market, we are hoping as consumers that this dietary product will be absorbed in an active form across the gastrointestinal tract and concentrate in active tissue sites, such as the articular cartilage,” Jessica says.
Through the development of the LPS model, Jessica, with assistance from Dr. Arnold, has evaluated potential dietary strategies for the young performance horse.
One of particular interest was an oral glucosamine product. The results of this study have been published in the “Journal of Animal Science.” Jessica hopes to continue to use this LPS model on other dietary implications.
“AQHA was really able to provide us with the opportunity to produce the foundational knowledge that was needed to be able to continue to advance in this particular area of focus,” she says. “For me, personally, the funding has assisted me with gaining industry attention to utilize and further develop this particular model to evaluate different dietary interventions relative to joint health.
“I appreciate all the Foundation has done. A lot of the research we've been able to do with this particular project has really set the foundation for my continued work in this particular area.”
Using the basic building blocks, Jessica is now working with master’s and doctoral students to help them perform their own studies. It's a process that doesn't stop.
“We are continuously refining our studies, and each student is taking it and adding their own flare and looking at new and upcoming biomarkers that may be used to predict the development of OA,” she says. “Personally, I'd like to continue looking at this particular LPS injection and compare dietary supplements among different age groups.”
Lameness can be costly. Osteoarthritis is common in older horses, but the joint damage often coincides with early growth in training.
Jessica is working to give horse owners more concrete evidence on dietary supplements and the potential effects of how the age of their horse might affect the efficiency of these products.
“I hope to provide consumers with the confidence to understand what is in their equine-based supplements and how these supplements are being incorporated in the actual joint space, to which they are supposedly eliciting their efforts,” she explains.
Jessica Leatherwood was an assistant professor of equine science at Texas A&M University, where she earned her bachelor’s, master’s and doctoral degrees. Prior to her return to Texas A&M in 2016, Jessica was the equine science coordinator at Sam Houston State University. She has conducted AQHA International horsemanship programs throughout Europe, Australia, New Zealand and China. Jessica’s research focuses on developing diets that may be effective in mitigating the over-stimulation of inflammatory processes within articulating joints of young performance horses. She received the Young Investigator Award from the American Quarter Horse Foundation in 2011, specifically intended for graduate students, to further her research.