From trail riding to endurance, lessons to racing, exercise in the heat has effects on the digestive tract.
Intensity of work is related to how much heat is generated during exercise but intensity is relative. Activity easily handled by a fit horse may require an extreme effort by one that is not fit. Also, fluid and electrolyte losses in sweat are greater for intense efforts but horses working for prolonged periods at lower levels may accumulate equivalent sweat losses. An additional factor for horses working for prolonged periods is less opportunity to eat and drink, possible changes in diet. Horses shipping in hot weather also have less opportunity to drink and their sweat losses in hot trailers can be considerable.
The body and intestinal tract coexist closely but there is normally little exposure of the body tissues/blood to intestinal contents because of proteins located between cells of the intestinal wall called tight junction proteins. It has been shown that increases in body temperature commonly seen with exercise can alter these tight junctions, resulting in cramping and diarrhea. Alterations in tight junctions are also believed to be related to the generally “sick” feeling that athletes can perceive after exertion and contribute to immune dysfunction.
High core body heat can also reduce the number and diversity of organisms in the digestive tract. Reduced efficiency of fermentation and lowered generation of volatile fatty acid fermentation products means less efficient use of fibrous feeds and less efficient absorption of nutrients and water.
We can’t completely avoid heat having an influence on the GI tract but can take some sensible measures. Make sure your horse has been properly conditioned for the work you do. This is no time of year for “weekend warriors”. Also guarantee adequate intake of salt/electrolytes and constant supply of water to avoid the disrupted intestinal function that comes with dehydration and electrolyte abnormalities.
Supplements containing ingredients like L-glutamine, Marshmallow root, Licorice root, Slippery Elm, sodium copper chlorophyllin and Aloe Vera can help soothe irritated linings while mannanoligosaccharides and beta-glucans provide gentle stimulation for the local gut immune system.
Probiotic supplementation after the horse has been cooled out from exercise could be helpful in restoring beneficial populations. This supports good fermentation, absorption and immune function. A blend of Saccharomyces cerevisiae yeast and bacterial species is best.
Diet can also be very helpful in supporting fermentation and levels of fatty acids as well as promoting good hydration both in the intestinal tract and throughout the body. Easily fermented and high soluble fiber supplements such as fructooligosaccharides, psyllium husk fiber (always wet before feeding) and beet pulp accomplish this. Regular use of a supplement with good digestive enzyme (amylase, lactase, cellulase, phytase, lipase, protease) activity can assist with small intestine functions so that the hind gut does not get overloaded.
Exercise and heat effects on gastrointestinal integrity and activity should not be ignored. Solid conditioning, reasonable work expectations and targeted support can make this manageable.