Digestive Health Through the Seasons

Digestive Health Through the Seasons

Photo: Anne M. Eberhardt/The Horse

A horse's digestion is closely tied to his overall health and well-being. Although people might be able to get away with a junk food-based diet for a while, a horse cannot, and food-associated diseases such as colic and founder will become an issue if a good diet is absent. And as seasons change, a horse's nutritional needs require a little tweaking in order to avoid illness and weight loss. With a little forethought and common sense you can maintain that all-important digestive health throughout spring, summer, fall, and winter.


During the spring pasture quality tends to be different than in the late growing season or during winter. This younger grass typically is richer and more nutritious than later in the season.

While many owners feel that that gradually introducing their horses to lush spring pasture is important for digestive health and stability, Brian Nielsen, MS, PhD., PAS, Dipl. ACAN, professor of equine exercise physiology at Michigan State University, suggests owners consider another train of thought.

"Spring pasture has a mix of both green and dormant plants," he explained. "If you pull (the average horse) off this and put them back on when everything is green, they will just gorge themselves. If you keep them on the pasture and they start to search out the little green stuff, they will be acclimated to the changes.

"However, if you have insulin-resistant horses, gradual introduction might make sense," he added. "New pasture growth high in fructans might cause some problems for them."

So, according to Nielsen, while there is some risk of colic and founder when turning horses onto fully green pasture cold turkey, the odds are most horses will handle the transition well.

If your horse is completely new to pasture (such as a Thoroughbred that has just come off the track), most veterinarians recommend turning out for an hour each day and extending each day by an hour or so to help the horse adjust gradually. If you're concerned about overeating, you might also consider putting a grazing muzzle on your horse.

Owners with good-quality pastures can count themselves lucky as the nutritional value of living forage is very high. But should you supplement with hay? Nielsen said you can, but you'll likely notice that your hoses ignore the hay altogether when adequate grazing is available. (Note: For information on what pasture plants grows best in your area consult your local extension agent.)


Summer in the southern parts of the country--especially the more arid areas--can feel worlds away from the northern parts. William A. Schurg, PhD, PAS, Dipl. ACAN, professor of animal science at the University of Arizona (UA), suggested that one method to consider for keeping horses cool in hot summer climates is to feed them less forage--a practice carried out at UA.

"(In the summer) we feed more high-fat and soluble fiber diets," he said. "Hay forages have a higher heat increment or heat of fermentation than more soluble starch-type feeds like grains or protein supplements. So in the summer months when the temperatures are reaching the 100ºF mark, we don't want to create excess internal body heat so we reduce the amount of dry forage that a horse eats and replace it with fats, oils, or concentrates, such as the newer low-starch, high-fat and soluble fiber products that create less internal heat upon digestion. Therefore, the heat of fermentation is lower and the horse doesn't have to struggle to rid his body of excess internal heat. Overall, he will be able to regulate his body temperature better."

Schurg suggested eliminating several pounds of dry hay from the diet per day during the summer and replacing the calories with a low-starch feed or mixture of oils (usually an omega-3 fatty acid source) as a topical dressing.

In the cooler parts of the country, where pastures are more standard during the summer months, people are sometimes fooled into assuming the grass they see is full of nutrition, but Nielsen cautioned it's easy to get tricked by all that tall grass.

"Tall mature grass is actually low in protein, energy, vitamins, and all the good stuff horses need (apart from fiber)," he explained. "The more mature the grass, the more stem it has and the less nutritious it is. Two thirds of nutrition in grass is in the leaves, so you want to have grass with a lot of leaves and less stem."

The best way to keep your pasture "young" is to mow it several times during the growing season, which will also keep the invasive weeds down and make the grass more palatable. Conversely, if your horse gains weight easily, consider letting the grass grow taller, which can help keep weight manageable.

"The problem here is that the horses will chew some areas short and leave the tall stuff," Nielsen cautioned. "The parasite load increases because the horses will hang out there, and overgrazed plants will have damaged root growth and be susceptible to dying off."


Fall is when horse owners in the south can breathe easier, but for their northern neighbors, fall means preparing for winter. For horses this could mean packing on some extra weight to prepare for winter's higher energy requirements.

"Go in (to winter) a little on the chubby side by increasing the hay," Nielsen advised. "It doesn't hurt to add some corn or vegetable oil to the diet ... if you do have a hard keeper, grain with fat added can be a good option.

"Sugar beet pulp is a nice fiber source high in soluble carbohydrates," he continued. "It is easily fermentable fiber so you don't have to worry so much about digestive problems. Incidentally, it's a high-energy source that is low in phosphorus (unlike some grains), which is an extra benefit because the horse won't have a high phosphorus excrement that's released into the environment."


Horse owners in northern climates know that on a bitter cold day, they can warm their hands by pushing them deep in their horses' coats. The heat that keeps horses warm on even the most unbearable winter day is produced inside the digestive tract, which is fueled by fermentation. In other words, horses have their own little central heating system. You can help keep that warmth flowing by providing the right materials. For the horse, this means fiber.

"When a horse digests long-stem fiber (hay), microbial fermentation occurs and heat is created," Nielsen explained. "This has a benefit to the horse in times of cold weather because fiber is digested slowly and heat is sustained for quite a long time."

Although Nielsen said it's difficult to pinpoint a precise amount to feed, an extra flake of hay on a cold day is generally a good idea. Other calories gained from fat and grains, such as corn, can still be used for warmth, although it won't produce that long, sustained heat. A horse will use that feed for whatever purpose it needs, whether it is running a race or keeping warm, but fiber will always generate heat.

Year-Round Water Needs

Water is the most essential nutrient for the horse. Plenty of clean, fresh water should be available to the horse at all times, but horses will also change their drinking patterns season to season.

Schurg says in southern parts of the country during the hot summer months, a horse's water intake increases from 4-8 gallons of water per day during 65ºF (18ºC) days to 20-40 gallons of water during 100ºF (38ºC) days. During extreme cool weather water intake might be compromised and the horse will drink significantly less than needed.

Feed intake is related to water intake, and it's generally believed that a horse will take in about a 4-1 ratio of water to feed on average.

"Inadequate water intake has a direct effect of feed intake and maintenance of digestive health," Schurg said. "Adequate water intake allows for a more uniform mixing of feed particles and aids in movement of digesta through the digestive tract and helps enzymes and bacterial to more effectively breakdown the digesta. Inadequate feedstuff breakdown increases risks of impaction and gaseous colics."

Schurg said he prefers owners offer horses water via a bucket or barrel rather than in the small automatic waterers. Horses like to put their lips and face down into the water to get a drink, and the small bowl automatic waterers don't allow the horse this option, he explained.

"Also, in our environment (in Tucson), we found that during the hot summer months horses that were in pens under roof began to have bouts of abdominal distress," he added. "We found that horses were not drinking enough water because the small bowl waterers were heating up to more than 100ºF and burning the horses' mouths. Ultimately, we placed barrel waterers in their pens and also soaked their hay prior to feeding to aid hydration."

Nielsen also noted that horses on fresh, green summer pastures get their water intake from different sources than they do in the winter.

"For instance, in the summer when forage is green, horses may drink less because there is moisture in the grass," he relayed. "In the winter all the moisture they need comes from the water tank."

To help your horse keep his body temperature up in the winter, make sure that his digestive tract is able to function at peak performance. That means ensuring he has a readily available source of drinkable water, Nielsen said, adding that snow alone does not suffice as a water source for horses.

"A horse would not be taking in enough water if you rely on him eating snow," he explained. "Also, a horse will use up a lot of calories getting that snow from the solid state to the liquid state, so it will be that much harder for your horse to keep his weight on."

More so, horses are much less likely to drink cold water than tepid water. Most water tank heaters keep the water a few degrees above freezing, and as long as there isn't any ice floating in the water, the majority of horses will find this temperature satisfactory. But if you have worries about a particular horse getting enough water, warming his water up could encourage him to drink more.

Take-Home Message

No matter what the weather, always make sure that hay is free of mold and dust, grain (if fed) is given in small meals, and, of course, water is readily available. Having your horse dewormed regularly and teeth checked routinely also contributes to proper digestive function. Good horse keeping along with monitoring changes in your horse's eating and drinking patterns will keep your horse moving easily from season to season and in good digestive health.

About the Author

Sharon Biggs Waller

Sharon Biggs Waller is a freelance writer for equine ­science and human interest publications. Her work has appeared in several publications and on several websites, and she is a classical dressage instructor.

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