As a follow up to the Manurology 101 post:
written for Traveller's Rest Equine Elders Sanctuary by
Amanda Blanton, DVM
Rappahannock Equine Veterinary Clinic
To understand how critical roughage is to a horse’s diet, it is necessary to have a basic understanding of the horse’s gastro-intestinal (GI) anatomy and how the horse’s GI tract handles different types of feed stuffs.
A horse’s GI tract consists of the mouth, esophagus, stomach, small intestine, cecum, large colon, small colon, rectum, and anus. It takes 48 to 72 hours for feed material to pass through a horse’s entire GI tract. Each portion of the GI tract has a specific function in digestion. The mouth’s functions are prehension (acquiring feed material), mastication (chewing/breaking feed into smaller particles), and swallowing. Feed material is then transported from the mouth to the stomach via the esophagus which has no digestive function of its own.
The horse’s foregut is composed of the stomach and small intestine. Most starches, protein, fat, vitamins, and minerals found within feedstuffs are digested and absorbed by enzymes in the foregut (primarily in the small intestine). The cecum, large colon, small colon, and rectum make up the horse’s hindgut which contains micro-organisms (bacteria and protozoa) that break down dietary fiber found in roughage into usable components. These micro-organisms are present in the equine hind gut to digest fiber because horses lack the enzymes required to break down fiber themselves. Due to the horse’s innate hindgut micro-flora, roughage is a necessary component to a horse’s diet. Otherwise, the micro-environment becomes instable and indigestion, colic, diarrhea, etc. result,
Micro-flora instability and resulting indigestion and colic are also caused by rapid changes in feeding routines because the micro-organisms adjust to the new feed slowly. As a result, colic and indigestion can be prevented when changing feeds by making necessary changes slowly.
Recommendations for the amount of roughage (hay, pasture, beet pulp, etc.) required to maintain a healthy hindgut are as follows: no less than 1 percent of body weight, which is 10 pounds/day for the average 1,000 pound horse. Overfeeding concentrates, or grain, can also be detrimental to a horse’s digestive health. When too much grain is fed to a horse, most of it is digested in the small intestine, but some of the feed will spill over into the hindgut where it is rapidly digested, producing large amounts of gas and acid. This excess gas can cause discomfort and result in colic, and if the amount of concentrate consumed is severe (like in a case of grain overload), toxins are released that can result in laminitis (or founder). As a result of the consequences of overfeeding grains, it is recommended that a horse be fed no more than 1 percent of its body weight in grain per day.
Because a horse’s gut functions best when small amounts of feed are moving through it regularly (like when a horse is grazing), it is also a good idea to feed a horse small (over) meals throughout the day. The best way to achieve constant filling of the horse’s GI tract is to maximize the amount of forage being fed in the diet and to minimize the amount of grain in the diet while meeting the horse’s feed and energy requirements. In other words, making forage, or roughage, the base of the diet and supplementing with grain to provide what is lacking in the forage.
This type of forage based diet becomes more difficult when dealing with geriatric horses due to the inability of many older horses to prehend (grab) and masticate (chew) well. This difficulty is due to the normal progression of geriatric tooth wear and tooth loss. Luckily, there are many commercial diets that are “complete” feeds, meaning that they contain both concentrates and fiber. A horse’s complete nutritional needs can be met by feeding these feeds alone; however, their need for long fiber bulk is not met if these feeds are fed exclusively. As a result, horses fed these senior or complete feeds alone often have soft, unformed manure. The mechanical bulk provided in roughage allows feed material to pass through the GI tract at a rate that improves digestive efficiency and reduces the risk of colic. Some examples of feedstuffs that add the necessary long fiber bulk to the diet while being more prehendable for older horses with dental imperfections are beet pulp (soak overnight before feeding) and soaked alfalfa/timothy cubes and pellets. Most of the “complete” or senior feeds also form nice mashes when water is added, making them more prehendable and digestible for the older horse. Contact your veterinarian for specific diet options for your horse.
In addition to processed sources of roughage, all horses, unless they are suffer from a disorder where limited turn-out is required, benefit from regular pasture turn-out. Not only is turn-out and access to pasture good for their minds and bodies, it also stimulates saliva production (even if they are old and drop most of the grass or hay they prehend) which helps buffer stomach acid and reduces the incidence of equine gastric ulcer syndrome.
In summary, keep the hind gut micro-environment happy by doing the following:
--Mimic the natural constant grazing of wild horses by feeding small, frequent meals or by providing free choice hay or turn-out
--Feed 1-1.5% of a horse’s body weight in roughage per day (~10# hay/1000# horse/day)
--Feed no more than 1% of a horse’s body weight in grain per day
--Provide a forage based diet with grain/concentrate supplementation
--Make feeding changes slowly, over at least a 10 day period
--Have a good relationship with your veterinarian and discuss your horse’s specific needs with him/her
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