Digestion And The Risk of Impaction Colic
Did you ever wonder why the horse’s digestive system seems so fragile or sensitive?
Did you ever wonder how horses survived climate change from rain forest to dry grassland and have adapted?
A horse may have digestive problems by simple acts of severe weather change, change in their routine or an abrupt change in the feed source; ranging from impactions, diarrhea, upset stomach, refusing feed or not eating.
There is actually a good explanation that scientists have researched; after analyzing fossil data alongside of records of North American climate changes. The researchers found that the animals diets shifted from rainforest fruits and leafy vegetables to the more abrasive diets found in grasslands.
When horses first came into being, they were located in a rain forest environment of vegetables, fruits and lush leafy greens. This would be like you eating a large veggie salad. As time passed on, the land went through a climate change from being a rain forest to a dry climate where the same vegetation would not grow. Only a dry grass land came into existence. The horses faced extinction if they did not adapt to the environment. Can you imagine if you changed today from eating a nice supple leafy veggie salad, to eating grass on your lawn or even dry hay? Your body and the horses were not designed to break down those fiber roughages for food source. In nature, the horses adapted to their environment – a successful survival strategy. The ancient ancestors of Equidae (The horse family) developed the ability to digest the dry climate vegetation grasses. Eating grass, which is a difficult to digest, was a successful survival strategy. During this period many species were unable to adapt to eating grasses and became extinct. However this survival strategy came with a price. Horses are non-ruminant herbivores of a type known as a “hind-gut fermenter.” This means that horses have a simple stomach, just like us. However, unlike humans, they also have the ability to digest plant fiber (largely cellulose) that comes from grass and hay.
They differ from other ruminants, such as cattle, sheep and deer, which digest fiber in plant matter by use of bacteria in a complex multi-chambered stomach to digest fiber by fermentation and use enzymatic digestion in the small intestines; a far more efficient digestive system. Horses developed, because of means of survival, a delicate but unique dual system. The foregut is where digestion of simple carbohydrate sources such as starch from grain occurs, and the hindgut is where the fibrous sources such as oat hulls, beet pulp and hay occur.
Foregut consists of: esophagus, stomach, small intestine and cecum.
Hindgut consists of: cecum and colon.
Digestion is by microbial enzymatic fermentation and takes place in the foregut ahead of the cecum; the crude protein digestion and virtually all soluble carbohydrate digestion. At this time the fiber is not broken down and moves on through the digestive tract, to be broken down later by the fermentation vat called the Cecum, and then absorbed in the colon.
The horses have adapted to breaking down fibers, but they are not a ruminant type animal like the cow. They are classified as non-ruminant. That is why they need to be watched carefully to avoid deadly complications.
The Digestion System and Why Horses are at Risk of Impaction Colic
Understand how the digestion works and why treatment used over the last 50 years is not working.
To have a better understanding of horse’s digestion, I have simplified each phase of the digestive system. This will give you a better understanding how each section works and why horses colic.
Mouth: Feeds are mixed with saliva in the mouth to make a moist bolus that can be easily swallowed. Three pairs of glands produce saliva. Horses will produce up to 10 gallons (85 lb.) of saliva per day. No wonder horses need water at all times to keep hydrated! Depending on the weather, horses will drink from 10 to 20 gallons of water a day. Drinking adequate amounts of water will lessen the risk of having impaction colic so check waters daily. I think dehydration is the number one cause of impaction colic.
Teeth: Horses need to chew their feed for better digestion to occur. By breaking down the feed stuffs, the enzymatic and microbial action can penetrate the plant cell walls making digestion more efficient. The horse needs healthy teeth to grind feed. Always examine teeth during the annual health check to ensure that they are wearing normally. The horse’s upper jaw is wider than the lower jaw, so sharp points often develop on the molar teeth. If your horse is dropping feed out of its mouth, it may be an indication that points have formed on the teeth and they are cutting the inside of the mouth as they chew. These points may prevent normal chewing which reduces the food value received from the feed and may predispose a horse to colic. Filing (or floating) the teeth will remove the points.
Esophagus: The esophagus is a simple muscular tube that takes food from the mouth to the stomach and is about 4-5 feet in length. A muscular ring, called the cardiac sphincter, connects the stomach to the esophagus. Because of the angle that it attaches to the stomach and the fact that this muscle is very strong this explains why it’s almost impossible for a horse to vomit.
Stomach: The stomach of the horse is small in relation to the horses’ large body. This limits the amount of feed a horse can take in at one time. The natural feeding habit of the horse is to graze on small amounts of roughages often. The average sized horse (800 to 1200 lbs.) has a stomach with a capacity of only four gallons. Feedstuff is broken down in the stomach by bacteria that produce lactic acid, other acids and the enzyme pepsin, creating “chyme”, a term used to refer to partially digested food as it moves through the digestive tract.
For full digestion to take place, feed may stay in the stomach for up to 24 hours before it moves on. The stomach works best when it contains 2 gallons of feed for full digestion to occur. The fact is that the stomach empties when it becomes 2/3 full, whether stomach enzymes have completed their processing of the food or not. Because of the design of the horses’ digestive system, it runs more efficiently when fed small meals often. However, horses are now housed in stalls or pens where grasses do not grow – horse owners ration the feed. Horses are now expected to eat large amounts of concentrate once or twice a day. If you feed a large amount of concentrated grains and hay at one time and the stomach becomes more than 2/3 full it may only stay in the stomach for as little as 15 minutes before it is passed on. This means the feed stuffs are not fully digested and may predispose your horse to impaction colic. To avoid this potential problem continuous foraging or several small feedings per day are preferable to one or two large ones. The rate of passage of food through the stomach is highly variable, depending on how the horse is fed.
It then leaves the stomach through the pyloric valve,
which controls the flow of food out of stomach and into the small intestine.
Small Intestine (Upper Gut): The horse’s small intestine, the major digestive organ, is 50 to 70 feet long and holds 10 to 12 gallons. After the food has been digested, it is absorbed through the walls of the small intestine and carried off by the blood stream to whatever cells need the nutrients. Nearly 70% of carbohydrate digestion and absorption and almost all amino acid absorption occur in the small intestine. It can take as little as 30 to 60 minutes for food to pass through the small intestine. Most food is digested and absorbed into the bloodstream from the small intestine, including proteins, simple carbohydrate, fats, and vitamins A, D, and E. Any remaining liquids and roughage move into the large intestine.
The small intestine contains three sections; the duodenum, jejunum and ileum.
Duodenum: The majority of digestion occurs in the duodenum as bile from the liver aids in digesting. Horses do not have a gall bladder, so bile flows constantly.
Jejunum: The Jejunum is important in re-absorption process of bile salts and absorption of nutrients during digestion and is the part of the small intestine where the majority of nutrient absorption occurs.
Ilium: This part of the upper gut is primarily a transition area between large and small intestines.
Cecum: The cecum is the first section of the large intestine; a pouch, about 4 feet long that holds 7 to 8 gallons of digestive chyme. It is a microbial fermentation vat, similar to the rumen in a cow. These microbes produce specialized enzymes that ferment and break down the cellulosic structures of fibrous feeds like hay or any material that was not digested in the small intestine. These bacteria feed upon the chyme, which will remain in the cecum for about seven hours, allowing bacteria time to start breaking it down. The microbes will produce vitamin K, B-complex vitamins, proteins, and fatty acids. The vitamins and fatty acids will be absorbed.
The unique design of the cecum creates a potential problem. Its entrance and exit are both at the top of the organ. This means that the feed enters at the top, mixes throughout, and is also expelled at the top. This design is the cause of problems when an animal eats a lot of dry feeds without adequate water, or if a rapid change of diet occurs. The reason horses must have their diets changed slowly is that the microbial population in a cecum is somewhat specific as to what feedstuffs it can digest. The bacteria in the cecum are slow to modify and adapt to the different chemical structure of new feeds. Too abrupt a change in diet can cause colic, as the new food is not properly digested. Both of these reasons may cause an impaction in the lower end of the cecum.
A good formula to follow is a concentrated grain based feed or new type hay:
Avoid Sudden Feed Changes: It takes about three weeks to develop a microbial population that can digest a new feed and maintain a normal flow through the cecum. A general rule for safely changing feeds:
- Week 1: Feed a mix of three-fourths of the old ration and one-fourth of the new feed.
- Week 2: Feed a mix of one-half of the old ration and one-half of the new feed.
- Week 3: Feed a mix of one-fourth of the old ration and three-fourths of the new feed.
- Week 4: Feed all new feed.
Colon: The large colon, small colon, and rectum make up the remainder of the large intestine. Microbial digestion continues, and most of the nutrients made through microbial digestion are absorbed here. Water is also absorbed, resulting into the formation of fecal balls. These fecal balls, which are the undigested roughage and mostly indigestible portion of what was fed, are then passed from the rectum.
Large Colon: The large colon is 10-12 feet long and holds up to 20 gallons of semi-liquid matter. It is made up of the right lower (ventral) colon, the left lower (ventral) colon, the left upper (dorsal) colon, the right upper (dorsal) colon, and the transverse colon, in that order. The main purpose of the large colon is to absorb carbohydrates, which were broken down from cellulose in the cecum. Due to its many twists and turns, it is a common place for a type of horse colic called an impaction.
Three tight bends in the large colon arise where these segments meet each other, and these are termed the sterna, diaphragmatic and pelvic flexures.
Small Colon: The small colon is 10-12 feet in length and holds only 5 gallons of material. It is the area where the majority of water in the horse’s diet is absorbed, and is the place where fecal balls are formed.
Rectum: The rectum is about one foot long, and acts as a holding chamber for waste matter, which is then expelled from the body via the anus.
What you should know about impaction colic:
As we’ve followed along the digestive tract, I have brought your attention to reasons a horse may have colic. It may be your horse’s teeth not properly maintained, over feeding at one time or a sudden change of feed, or not adequate intake of water. Not drinking enough water can be simply as a severe weather change. Horses drink when weather is warm, but if it suddenly drops to 20 to 30 degrees, or lower overnight, the horse does not feel thirsty or hot the next day, so they do not drink adequate amounts.
Impaction Colic is the number one killer of horses. Feed stuffs must be adequately broken down through digestion and flowing properly through a well hydrated horse. If not, the results are large masses of the chyme moving slowly and actually being trapped in the colon. Remember as explained above, the colon keeps doing its job as usual, pulling out the moisture to make fecal balls. When movement of digestion is slowed down, the colon actually pulls so much water out of the feed stuff, that it is now sticking (adhering) to the mucosal lining.
If given mineral oil as a treatment for impaction colic, it may not work because the barrier made in chyme sticking to the mucosal lining. The oil is not getting through to the other end and you do not see it being eliminated. Also, giving muscle relaxants (NSAIDs) as a treatment for impaction colic will not work because you need the smooth muscles to help with peristalsis (wave like movements) in moving partial digested feed stuffs through.
“SayWhoa!” to horses in distress! This product assists in reversing the situation and aids in bringing body fluids back into the colon which supples up the mucosal lining enabling release of the adhering feed stuffs. Then the ionic solution of calcium plus other natural ingredients aid in promoting smooth muscles needed for peristalsis which assists in elimination of retained stools. SayWhoa! has been on the market for some time and is available across the United States and Canada. Why wouldn’t you keep this on hand; with a 5 year shelf life, no temperature control and the horse just swallows it with an included oral dosing syringe (even your care taker can administer). Use as your first defense when you see signs of colic strike. For more information, go to www.HorseSenseSolutions.com or call 800-448-8180. See why veterinarians recommend this and leading trainers won’t be without it.
By: Reba Martinez – Horse Sense Solutions – Different Products for Different Digestive needs