Equine Nutrition for Well and Sick Horses

Sophisticated technology is quickly evolving and leading to a deeper understanding of the role nutrition plays in managing disease and overall wellness

Nutrition plays a key role in helping sick horses and keeping healthy ones active and performing well. iStockPhotos.com

In many ways, the nutritional challenges of today are unchanged from years past. Metabolic problems, laminitis and overweight or sedentary horses have always presented nutritional challenges, according to Joe D. Pagan, PhD, founder and president of Kentucky Equine Research (KER).

Sophisticated technology is quickly evolving and leading to a deeper understanding of the role nutrition plays in managing disease and overall wellness. “In the last few years, there has been a real uptick in the ability to measure gene response and how nutrients affect gene expression,” he said.

Pagan anticipates that with this level of diagnostics, horses will be treated as individuals based on their response to nutrients rather than as a homogenous animal population.

“Understanding the equine genome and how nutrients affect gene expression will allow veterinarians to modify a horse’s diet,” he said.

Three areas of interest among researchers include the effect of nutrition on muscle disease, the role nutrition plays in immunology and how nutrition impacts inflammation. 

In the article that follows, we’ve highlighted current projects exploring each of these areas.

Muscle Disease and Nutrition

Equine nutrition research is following on the coattails of human medicine, especially for diseases like Type 2 diabetes, Pagan said.

At Michigan State University, Stephanie Valberg, DVM, PhD, DACVIM, ACVSMR, is leading research that is examining the varying underlying causes associated with different myopathies. For example, type 1 PSSM is due to a gene defect that causes the horse’s muscles to continually make glycogen, the storage form of sugar in the muscle.

“By feeding a low, nonstructural carbohydrate diet, insulin stimulation is reduced, and that minimizes the amount of sugar available and the stimulation of synthesis of glycogen in the muscle,” she said. “We can also provide fat as an alternate form of energy for PSSM1.”

Determining whether the diet of horses with type 2 polysaccharide storage myopathy (PSSM2) should be different from that of horses with type 1 polysaccharide storage myopathy (PSSM1) is a top priority, she said.

As horses are evaluated and treated on a more individualized basis, understanding distinctions between similarly related myopathies is increasingly important. Valberg classified this as one of the top three current trends in nutrition as it relates to muscle disease.

Valberg said that the impact of specific amino acids on muscle mass and topline―as well as vitamin E deficiency that can lead to reduced muscle mass―are two other trends she has observed in relation to nutrition and myopathy.

“For each muscle disease, we try to figure out what causes it and target a treatment to get around the problem or replace the deficiency,” she said.

Horse owners are becoming more aware of supplements and diets for horses from the internet. This constantly challenges veterinarians to keep up with what research there is (or isn’t) to substantiate claims that are made.

“I think there needs to be a continuing partnership between nutritionists and veterinarians to develop or apply specialty diets for horses,” Valberg said. “The veterinarian is familiar with the individual horse’s needs and the medical issues that must be addressed, and the nutritionists have a wealth of knowledge that can be used to design the appropriate diet.”

Inflammation and Nutrition

There is a lot of interest in anti-inflammatory nutritional supplements, both in athletic horses and older horses. David W. Horohov, PhD, director of the Gluck Equine Research Center at the University of Kentucky, is currently studying exercise-induced inflammation.

“In one study, we examined the impact of a dietary supplement on 2-year-old Thoroughbreds in race training,” he said.

Horses that received a dietary supplement exhibited a decreased inflammatory response to exercise and a conditioning effect. This conditioning was seen as an overall decrease in the inflammatory score of the horses, and it was a significantly greater decrease in those receiving the supplement.

“These data support the notion that nutritional supplements might be used to alter inflammatory responses in the equine athlete,” he said.

The supplement contained multiple ingredients, so it was not possible to identify which specific component was responsible for the anti-inflammatory effect. There are a number of different nutritional supplements that are purported to have immunomodulatory activity, but not all of these claims have been confirmed under rigorous testing. In general, avoidance of pro-inflammatory nutrients (e.g., n-6 polyunsaturated fatty acids) and the use of n-3 PUFA, which are anti-inflammatory, has been shown to be effective in a number of species.

“More work is needed to identify the potential benefit of other supplements in horses,” Horohov said.

As the industry moves more toward evidence-based veterinary medicine, the role of research, both clinical and applied, becomes vitally important, Horohov said. This is particularly true as it impacts equine nutrition.

“While it is clear that nutrition can have an effect on inflammatory responses, I would recommend caution in making specific recommendations unless the data supports the label claim,” Horohov said. “It is also important to consider the overall health and activity level of the horse when making any recommendation.”

As this is an area of intense interest and ongoing research, it is important to stay abreast of the new information that is being generated. Horohov and his colleagues publish their work in veterinary-related journals and present the results at veterinary conferences.

“We are also happy and willing to talk to veterinarians about our work,” he said. “As there is a significant amount of information available on how diet can influence immune function, including inflammatory responses, this conversation should happen whenever the opportunity presents itself.”

Immunology and Nutrition

For the older horse population, researchers are interested not only in the anti-inflammatory effects of nutrition, but in understanding how nutrition can support the age-related decline in immune function.

Amanda Adams, PhD, an assistant professor at the University of Kentucky, is leading a project studying how nutrition can support the immune system as horses age. She has recently conducted two studies investigating this question.

“We have an interest in understanding how nutrition can influence inflammatory responses after feeding a meal, as this may play a role in some of the metabolic diseases of the horse―in particular, equine metabolic syndrome,” she said.

In studies conducted thus far, results indicate that proper nutrition can decrease inflammation in older horses, as well as support immune function to vaccination.

“These findings are quite exciting, as they support the fact that nutrition can be a powerful tool in modulating immune responses―especially in the senior horse population and, likely, the metabolic-syndrome horse,” Adams said.

In the studies with the older horses, it was actually a proprietary prebiotic formulation that was found to be immunomodulatory.

“We tend to forget that a significant percentage of the immune system is located in the gut, which is critical for supporting the health of the animal,” she said.

While quite a bit is known about probiotics and prebiotics, not enough is known about what bacteria are most beneficial and how much to feed for how long. These are questions that need to be answered with more research.

“Giving too much of these probiotics and prebiotics actually could do more harm than good,” she cautioned.

Ongoing Challenges

As research continues to pinpoint specific nutritional feeding guidelines for horses with specific diseases, getting horse owners and caretakers to follow label instructions remains a challenge.

“Feeding compliance remains a challenge,” said Abby Keegan, equine innovation and application lead for Cargill Animal Nutrition’s Nutrena brand.

Following the directions on a feed label might seem basic and rudimentary, but it is often overlooked. She compared the importance of following a feed label to a person following a doctor-recommended dosage for antibiotics.

“If you take a child to the doctor and medicine is prescribed, you receive specific dosing directions based on the child’s body weight. If the directions aren’t followed, the medication probably won’t work right,” she said.

Similarly, feed manufacturers formulate rations based on age, weight and activity level, among other factors. Keegan said she sees this compliance issue as an opportunity for veterinarians to start conversations with clients about nutrition and feeding.

Even if a horse looks healthy and shiny, it doesn’t mean he isn’t deficient in specific nutrients or that he is receiving the accurate ration, she said.

Nutrena offers two tools veterinarians can use as conversation starters with clients. A forage analysis produces a bar graph outlining any gaps or deficiencies in calories and trace minerals. An online tool (toplinebalance.com) from Cargill is a visual resource with eight questions that can aid in evaluating a horse’s topline.

“While it’s not really anything new, having conversations with clients about feeding compliance and forage composition is providing clients a better understanding of the health of each individual horse,” she said.

Over the past 10 years, there has been an exponential increase in technology to evaluate and create nutritional guidelines for healthy horses as well as for sick horses. 

KER’s Microsteed software is another tool for creating custom-tailored rations based on the nutritional requirements of individual horses and making feeding recommendations based on those results.

“If you know the genetic makeup of a horse, it becomes helpful in managing those horses,” Pagan said. “This is very different from 35 years ago when I started in my career. These are very interesting times.”

Take-Home Message

While many veterinarians don’t involve themselves in day-to-day nutrition evaluation or recommendations, this is a key area of horse health. Working with a private or university-based equine nutritionist or a specialist from a trusted business partner can help your equine veterinary practice better serve clients who have nutrition questions or problems.

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