Colic and/or founder (laminitis) are problems of major concern to horse owners.
Both conditions can vary in their seriousness from slight cases to cases that can kill horses or severely compromise them for the rest of their lives.
There are many causes of colic and founder. Most causes are known, although some are not fully understood.
One known cause of colic and/or founder is starch overload from grains or commercial concentrates.
Starches are carbohydrates that are highly soluble and quickly digestible into sugars.
Much of the research in this area of nutrition has been performed by Dr. Gary Potter and his graduate students in the Texas A&M University department of animal science — equine sciences section.
In this column, grains and commercially prepared concentrates are considered as the same.
The digestive tract of the horse is divided into two sections, based upon the type of digestion that takes place in those sections.
The foregut includes the stomach and small intestine. The hindgut includes the cecum, large colon, small colon and rectum. Grains are basically digested by enzymes in the foregut. Roughages such as pasture grasses and hays are basically digested by microbial, bacterial and protozoan fermentation in the hindgut.
The horse’s stomach has three limitations that can lead to colic and/or founder, if a horse is fed grains improperly.
First, the stomach is small in size, holding only 2 to 4 gallons.
The stomach starts emptying its contents into the small intestine when it is only about two-thirds full.
Second, there is a small pocket of hindgut-like microbes in the primarily enzymatic stomach.
Under certain conditions, these microbes can produce large volumes of gas very quickly.
Third, the sphincter muscle, where the esophagus enters the stomach, allows feed to pass down into the stomach, but not the reverse. This means the horse can not vomit. The horse also can not belch excess gases up out of its stomach.
If a horse is overfed grain, an energy concentrate or has a grain ration changed without a transition period, problems start occurring in the foregut. The grain can’t be vomited up out of the mouth. The microbes produce more gas than normal from the excess grain.
An excess amount of partially pre-digested grain is dumped into the small intestine. The rate of passage now adds to the problem.
The excess amount of partially digested grain passes through the 70 feet of small intestine at a rate exceeding one foot per minute.
A lot of the starch in the grain is absorbed from the small intestine, but an abnormally high amount is still dumped into the hindgut, causing more problems.
The overload of starch reaching the hindgut is fermented into energy juices. With this process comes the abnormal production of elevated levels of lactic acid and other abnormal toxins.
These byproducts are now absorbed from the hindgut into the blood stream and are pumped throughout the body. Excess gas production occurs in the hindgut.
The abnormal acidity level of the hindgut causes a change in the microbial population.
The challenge to the attending veterinarian is to reverse all these processes and get the horse’s body chemistry back to normal as soon as possible.
There are about 30 commonly accepted feeding management guidelines horse owners can follow to alleviate or minimize digestive disorders in their horses.
Specific grain feeding guidelines include:
• Only feed horses primarily high-quality roughages and feed grains or commercial concentrates, to help meet nutrient requirements.
• Feed grains according to the weight of the horse.
• Feed only high-quality fresh grains.
• Space multiple feedings throughout the day and never feed more than .7 percent of a horse’s body weight at any feeding. For example, 7 pounds of grain or concentrate for a 1,000-pound horse.
• Feed at the same time each day.
• Avoid abrupt ration changes, particularly when going from a lower-energy density feed to a higher-energy density feed.
• Encourage fast-eating horses to eat slower through stall design, feeder design or placement or by putting large objects in the feeders.