Look through any equine supply catalog or go into any tack or feed shop, and you’ll likely encounter pages and shelves full of supplements. Supplements aimed at improving gastrointestinal (GI) health are especially popular, given that research has shown most performance horses suffer from gastric ulcers.

Melyni Worth, PhD, PAS, of Foxden Equine, a nutritional supplement company, spoke about common ingredients in equine supplements aimed at improving GI health at the 15^th Annual Mid-Atlantic Nutrition Conference in Hunt Valley, Maryland, on April 6, 2017.

“Since the horse has been domesticated, GI disruptions have been an issue,” Worth said. “Very often, these issues are handled best by changing management.”

Ingredients Targeting Ulcers

In humans, research has shown hydrogen ion inhibitors, such as the drug omeprazole, can contribute to osteoporosis. Long-term studies haven’t been done in horses. Nonetheless, other acid buffers, although not proven to cure ulcers, are common in equine supplements aimed at managing the condition. These include calcium, magnesium, and aluminum salts. Sodium bicarbonate, commonly known as baking soda, is also a natural acid buffer, but too much can disturb normal electrolyte balance, Worth said.

Ulceration in the small intestine is less common than in the stomach, but impaction colic is still a risk. Similarly, the large intestine is at risk for physical blockage and even ulceration. Unfortunately, it’s difficult to diagnose ulcers in the small and large intestines, Worth said. Properly balanced, forage-based diets and plenty of water are the best places to start for preventing GI disturbances, said Worth.

Beta-glucan. Beta-glucans are sugars derived from the cell walls of fungi that absorb fats and fatty acids. Beta-glucan is a common ingredient in supplements, but there’s no evidence it is useful for managing ulcers.

Mucilage providers. Mucilage is a plant-derived polysaccharide (string of sugar molecules bonded together). Mucilage is a viscous, gelatinous substance that can coat damaged tissue, such as an ulcer. It won’t cure ulcers but might help protect damaged tissue. Common sources of mucilage include flaxseed, chia seed, aloe vera, hydrolyzed collagen, pectin, and lecithin. Additionally, slippery elm is a medium-sized tree with an inner bark that can be powdered and mixed with water to form a mucilage.

Other ingredients. Sea buckthorn berries are rich in vitamins C and E, fatty acids, and lignans and have shown promise in reducing the severity of gastric ulcers. Some other natural remedies, such as marshmallow root and licorice, have not been fully investigated in managing ulcers in horses, Worth said.

Take-Home Message

The number of supplements on the market geared toward managing GI health can feel overwhelming. The key is to know what each ingredient is and if it has any real effectiveness. Buy products from reputable manufacturers, and seek the advice of a nutritionist before supplementing your horse. If you suspect your horse suffers from ulcers or other abdominal pain, contact your veterinarian immediately.

Horses carry billions of passengers with whom they have a mutually beneficial relationship. No, they’re not his human riders—they’re the plethora of bacteria that make up his gut microbiome.

These bacteria don’t exist in a vacuum, but rather develop cooperative and competitive interactions within the horse’s digestive tract. The bacteria utilize food sources, are sensitive to pH and salinity, and have populations largely determined by the horse’s diet. In turn, bacteria produce B vitamins and volatile fatty acids (VFAs), on which the horse depends for energy production.

Does this sound complex? That’s because it is! To help simplify the topic at the 2017 Mid-Atlantic Nutrition Conference, held April 6 in Hunt Valley, Maryland, Amy Biddle, MEd, PhD, of the University of Delaware Department of Animal and Food Sciences, presented an overview of the equine gastrointestinal microbiome.

“The bacteria are master biochemists,” Biddle said. “They are extremely metabolically flexible, can adjust to the environment, and there’s nothing wasted in that system. We know there are differences in the bacterial populations found in horses with and without equine metabolic syndrome, young and old horses, horses with colitis versus without, and semi-feral and domestic horses.  How those microbiome differences translate into health outcomes is not well understood."

Understanding these differences has become the focus of Dr. Biddle’s research.

Foregut

The horse’s stomach and small intestine make up the foregut. Biddle said the stomach has a microbial factor and is home to bacterial species including Lactobacillus, Streptococcus, Veillonella and members of the Proteobacteria (a major phylum of gram-negative bacteria, including many pathogens such as Salmonella).

Lactobacillus and Streptococcus are lactic-acid-producing bacteria (LAB), which utilize any available soluble carbohydrate. On the other hand, Veillonella, Lactobacillus, and Streptococcus utilize lactic acid to make other VFAs. Proteobacteria include a variety of gut bacteria and are often found in soils. There are no protozoa or fungi in a normal horse’s stomach.

Helicobacter is a cause of gastric ulcers in humans, but has not been found in horses, Biddle said. However, Lactobacillus and Streptococcus have been associated with equine gastric ulcers, but probably do not cause them. These bacteria likely take advantage of damaged tissue, possibly making it harder for ulcers to heal.

The small intestine contains a variety of bacterial species. Different species are found along different points along the digestive tract, including, but not limited to, Lactobacillus and Streptococcus species. Material not digested by enzymes in the small intestine such as cellulose and other fibers, enter the cecum and large intestine.

Hindgut

The cecum, large and small colons and the rectum make up the horse’s hindgut. The cecum is essentially a large fermentation vat. For the bacteria, it’s all about finding energy and surviving in an environment that doesn’t have a lot of oxygen (called anaerobic). Volatile fatty acids are a product of fermentation, and can meet more than 50% of a horse’s energy needs over time. The production of VFAs for energy takes time, and results in a slower, steadier release of energy. Interestingly, Biddle said, in humans only about 6-10% of our energy needs come from VFAs produced during fermentation.

Fore- and Hindgut Differences

The foregut is dominated by LAB, whereas the hindgut is more diverse. There are less LAB and more anaerobic bacteria such as Clostridia and other cellulolytic bacteria. From a practical standpoint, this makes sense, as cellulolytic bacteria are necessary to break down fibers and cellulose not digestible by enzymes in the foregut.

Take-Home Message

The equine microbiome is a diverse ecosystem that provides vitamins and energy to the horse. The population of bacteria is determined by diet, life stage, health status, stress, and even season and time of day.

In general, diets higher in fiber and fermentable material encourage the growth and health of the hindgut bacterial ecosystem. In addition, the types of bacteria vary based on location in the digestive tract. There is much to be learned about the microbiome as the scientific community is just beginning to scratch the surface. 

We’ve all known and loved that special senior horse—the seasoned teacher, the care-taker, or the ruler of the barn. And while aged equines are common today—approximately 11.4% of the U.S. horse population is more than 20 years old—this wasn’t always the case. Advances in research, veterinary care, and nutrition have all aided in giving horses a chance at longer, healthier lives.

For example, we knew little about aging horses’ physiology until the early 1990s. That’s when Karyn Malinowski, PhD, professor and director of the Rutgers University Equine Science Center in New Brunswick, New Jersey, and colleagues began their research on the topic. Since then, they’ve made crucial discoveries.

Malinowski shared some of the most important findings from over the years at the 2017 Annual Mid-Atlantic Nutrition Conference, held April 6 in Hunt Valley, Maryland.

Exercise is Important

Scientists generally agree that horses typically begin to show physiological signs of aging by 20 years. With age, their aerobic capacity declines and they can develop arthritis, insulin resistance, and changes in body composition and immune function. But exercise and training can actually attenuate many of these age-related declines, improve body condition, and decrease insulin resistance.

“Exercise and exercise conditioning for older horses is a good thing,” Malinowski said.

In one study Malinowski worked on, older horses showed a significant decline in percent body fat and an increase in muscle mass after 12 weeks of exercise training.

“The horses looked great,” she said. “They actually waited at the gates to come to the Equi-Ciser (a horse walker) for their workouts.”

Thermoregulation

Senior horses also experience a decrease in their ability to regulate body temperature (called thermoregulation), because the heart works harder to get blood to the skin and tissues. Exercise can certainly help keep the heart strong, but older horses will likely still have some difficulty with thermoregulation in extreme temperatures.

Hormonal Changes

Age also affects the endocrine (hormonal) system. Specifically, Malinowski said, “cortisol is necessary to mobilize glycogen stores. In older horses, there is a blunted response of cortisol concentrations to exercise, which may put the older horse at a disadvantage.”

This decreased cortisol response can be somewhat mitigated by exercise training, but is not completely restored to that which younger horses experience. In sum, it appears to be a little harder for the older horses to utilize and restore energy reserves, making recovery time longer.

Inflammation

Malinowski also touched on the low-grade, chronic state of inflammation, defined as an increase in inflammatory cytokines, senior horses experience called “inflamm-aging.” She said inflammation increases with obesity, and calorie-restricted diets resulted in a decrease in some inflammatory proteins.

In addition, heat shock proteins (HSPs), which play a role in proper cell functioning, including insulin signaling, increase to a lesser degree in older horses compared to young after an acute bout of exercise. This could have additional implications for insulin sensitivity and recovery from exercise.

Take-Home Message

Seniors don’t necessarily have to be race-ready or prepared for competition, but keeping an older horse exercising has many physiological benefits. And while they need some special consideration when it comes to warming-up, exercise intensity, and cooling down, Malinowski said “exercise is necessary for the continued well-being of older horses.”

Organizers have lined up speakers for two days of sessions, with an equine-specific track taking place April 6. Speakers and topics are scheduled in include:

• Physiology of Aging in Horses—Karyn Malinowski, PhD, Rutgers University
• Feeding Management of the Endocrine-Challenged Horse—Lisa Tadros, DVM, PhD, Dipl. ACVIM, Michigan State University
• Exploring Seasonal Allergies in Horses—Katherine Williamson, DVM, Purina Animal Nutrition
• Can Nutrition Be Used to Boost the Immune System?—Lori Warren, PhD, PAS, University of Florida
• Gut Microbiome Overview—Amy Biddle, PhD, University of Delaware
• Sorting Out Common Ingredients In Equine Supplements—Melyni Worth, PhD, PAS, Foxden Equine
• Probiotics and Prebiotics in Horse Feed: What’s the Difference?—Marty Adams, PhD, PASSouthern States
• Digestive Feed Supplements and the Gut Microbiome—Panel Discussion

The conference is open to veterinarians, students, trainers, breeders, owners, and anyone else interested in learning about horse health and nutrition. Attendees will receive lunch and the opportunity to ask questions of all the speakers.

The conference is hosted by the Maryland Feed Industry Council, University of Maryland, Pennsylvania State University, University of Delaware, Virginia Polytechnic Institute and State University, Rutgers University, American Feed Industry Association, and the United States Department of Agriculture.

Pre-registrations are encouraged and can be completed online at ansc.umd.edu/extension/mid-atlantic-nutrition-conference/registration-information. Additional conference information is available at ansc.umd.edu/extension/mid-atlantic-nutrition-conference. For information on sponsoring the event, contact Jennifer Reynolds at 301/405-1547.