The production of gas in the gut (gastrointestinal tract) is normal for all mammals and especially for those animals whose gut is designed to eat large quantities of plant materials. Horses are classified as non-ruminant herbivores. Their hindgut, which includes the cecum and colon, is the major site for fermentation of the plant materials that are not (or can not) be digested in the foregut through chemical and enzymatic digestion. In the fermentation process, it’s the job of the microorganisms to digest the plant materials and produce selective nutrients and energy that are available to the horse. Gas is a by-product of the fermentation process and the horse’s gut is capable of moving the gas though the colon to be released.
Excess gas production, which has the potential of causing a first class bellyache, known as colic, can result from numerous factors. These factors include inadequate fiber in the diet, inadequate exercise, inadequate consumption of water (note: fiber and exercise influence water consumption), inadequate management routine, certain drugs, especially antibiotics, over feeding starchy feeds, changes in feeds and amount fed, inconsistent daily meal frequency and amounts fed, and (perhaps the cause that will step on the toes of horse owners) inadequate nutritional management experience and knowledge.
Beet pulp and soy hulls contain a type of fiber that is fermentable and is broken down by the microorganisms that live in the gut. The grasses that are fed via pasture and hay also have some fermentable fiber as well as the fiber that is classified as insoluble fiber. If there is inadequate forage provided, and the horse is fed a large quantity of fermentable fiber, then excess gas production could occur. Another scenario is if large portions of grain type feeds (in which major ingredients including corn, oats, and/or barley) are fed, then an excess gas production could occur. Any combination of factors listed in the first paragraph can cause excess gas production. The bottom line is that nutritional management of the horse plays the most important role in his gut health. Nutritional Management does not come from what we read on the internet, it’s a result of time, experience and education.
In addition, there some horses whose gut may be more sensitive to fermentable fiber type feeds. Through my 40+ years of experiences with horses as an owner, breeder, farm manager, university professor, and nutritional consultant, I have not had one horse that could not be easily managed with a diet that includes fermentable fiber such as beet pulp and soy hulls.
Summary: Beet pulp and soy hulls:
Are important feedstuffs in the nutritional management of horses.
Are safe sources of energy in balanced concentrates to fuel the horse in whatever he does.
Are solid ingredients with other feedstuffs that are formulated for a balanced concentrate mix that will complement the forage portion of the horse’s diet.
Have bulk laxative like properties that will assist the gut to contract with consistency and regularity as well as maintain a healthy microorganism population in the gut.
The bottom line: the information provided by your veterinarian is incorrect.