Feeding horses: Back to the basics, Part 1 (Animal Science Update)
Many people who care for horses might be fully capable of feeding horses and keeping them healthy —but do they really know the basics behind why we feed them the way we do and what they actually require?
This article and a few coming in the next few months will take us through just this: The Basics of Feeding Horses!
First, the horse’s digestive system has a few limitations that require them to eat certain things in certain amounts.
Horses are non-ruminant herbivores or hind-gut fermentors. Unlike their ruminant counterparts, such as cattle, sheep, goats, etc., their small stomach only has a capacity of two to four gallons for an average-sized 1000-pound horse.
This limits the amount of feed a horse can take in at one time. Equids have evolved as grazers that spend about 12 to 18 hours a day grazing pasture grasses allowing for a slow trickle of feed through the stomach.
The stomach serves to secrete hydrochloric acid and pepsin to begin the breakdown of food, that enters the stomach. Unlike the human stomach, horses secrete the acid around the clock, which could put the horse at risk for gastric ulcers if the stomach is left empty for extended periods of time.
Horses are unable to regurgitate food so if they overeat or eat something poisonous, vomiting is not an option.
Horses are also unique in that they do not have a gall bladder to store and concentrate bile.
They just rely on what the liver produces for their fat metabolism. This makes high fat diets difficult for them to digest and utilize.
Horses can digest up to 20-percent fat in their diet, but it takes weeks for them to adjust to levels that high because a natural forage rations without any supplementation contain only 3 to 4 percent fat.
We will talk in a future column about different feeds that contain higher concentrations of fat.
The horse’s small intestine is 50 to 70 feet long and holds 10 to 23 gallons depending on the size of the horse.
Most of the nutrients (protein, soluble carbohydrates and fat) are digested in the small intestine. Most of the vitamins and mineral are also absorbed here.
The horse’s small intestine is quite similar to ours and most other domestic species in terms of its structure and function.
Most liquids are passed to the cecum, which is 3 to 4 feet long and holds seven to eight gallons.
Detoxification of toxic substances occurs in the cecum. It is also very similar to the rumen of cattle or other ruminant species in that it contains bacteria and protozoa that ferment any other structural carbohydrates found in the fibrous forages they eat.
The fermentation by the microbes will break down the fibrous feeds into components that they can then absorb and use as energy (some vitamins are also produced).
Passage through the cecum for most forages is about 38 to 48 hours.
This give the microbes time to ferment as much of the feed material as they can before it gets passed on to the colon.
The large colon, small colon and rectum make up the rest of the large intestine. The large colon is 10 to 12 feet long and holds 14 to 16 gallons.
It consists of four parts with three flexures or turns that allow it all to be housed in the abdomen of the horse: right ventral colon, sternal flexure to left ventral colon, pelvic flexure to left dorsal colon, and diaphragmatic flexure to the right dorsal colon. The pelvic flexure is the most common place for impaction.
The small colon is the last 10 feet that leads to the rectum. It holds only 5 gallons of material and is responsible for the remainder of the water absorption and making fecal balls.
So now when you go to the barn to feed your horse maybe you will think a little bit about what goes on inside during their digestive process. Stay tuned for more horse feeding basics when we talk about the nutrients horses need to survive and specifically how to feed different classes of horses!
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