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Equine Nutrition in the
21st Century
Dr.
Judy Reynolds, Ph.D., P.A.S., Divisional Equine Technical
Specialist, ADM Alliance Nutrition. |
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Want to know what to feed your
horse? Here are the latest
recommendations.
Why
should it matter if we are in the 21st century or any other
century as far as equine nutrition is concerned? Actually, the
science of equine nutrition is very different today than it was
only a short time ago. As we learn more about how horses digest
and utilize nutrients from feeds, and as more feeds become
available, our feed choices broaden and change. We have recently
learned that digestibility of a feed is almost as important as its
nutrient content. We also now have many newly available feeds,
like beet pulp, soybean hulls and rice bran, which come from the
human food manufacturing industry. Following is a discussion of
current equine nutrition topics, starting with the equine
digestive tract.
The Equine Digestive Tract
No matter what your horse looks like on the outside, and no matter
what job you ask him to do, he has one thing in common with all
horses--his digestive tract. Everything he eats must be processed
through that tract in order to be used by his body for energy,
growth, reproduction and maintenance of health (See Figure 1).
(Click image to enlarge)
Horses
are grazing animals with digestive tracts best suited for eating
forages for 15-20 hours per day. They have relatively small
stomachs, which hold only about as much as a 5-quart ice-cream
pail. The actual physical capacity of the stomach is larger, but
the equine stomach begins to empty when it is only two-thirds
full. This is a safety mechanism to prevent lethal stomach
rupture, since horses cannot vomit. Feed proceeds from the stomach
through the small intestine, a 70-foot-long, tubular-shaped organ,
where most of the starch, sugar, fat, vitamins and minerals and
about half of the protein from the feed should be digested and
absorbed into the bloodstream. The remaining nutrients and the
plant fibers continue on to the hindgut (See Figure 2 --
Simplified Digestion in Horses).
(Click image to enlarge)
Horses
have huge fermentation vats in the hindgut that hold 23-30 gallons
of fibrous material while billions of bacteria and other organisms
work to digest it. Fiber-digesting bacteria produce volatile fatty
acids (vfa), or very short-chain fats, that are used by bacteria
and horses for energy. In fact, horses on total forage diets
receive 70% of their energy from these vfas. Some of the remaining
protein and some minerals, especially phosphorus, are absorbed
from the large intestine, along with water, which is recycled
within the body. Bacteria in a healthy horse’s hindgut also
produce B-vitamins that can be used by the horse.
The
equine digestive system is very efficient if horses are fed mainly
grass or hay. But, if we feed more than a few pounds of grain in
meals, the system doesn’t work very well. Grains are very high in
starch (50-75%) compared to grasses and hays (<10%), which the
digestive tract is designed to process. Often, the excess grain
starch can’t be digested in the beginning of the tract by the
horse’s enzymes for several reasons:
-
He just doesn’t have enough
enzymes,
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The starch is too compact to
be broken down,
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There isn’t enough time,
because most feed goes from the mouth through the
foregut and into the hindgut in less than 6 hours.
Starch
entering the hindgut is used, by starch-digesting bacteria, to
produce lactic acid. The addition of lactic acid, to the hindgut,
results in a lowering of hindgut pH. Many of the beneficial,
fiber-digesting bacteria cannot tolerate the more acidic
conditions, so they die and release toxins into the hindgut. The
presence of these toxins often results in colic and founder. This
cascade of events begins with high-grain (starch) rations and ends
with colic and founder. Research results show that feeding 5
pounds or less of grain-based feeds daily greatly reduces the risk
of colic and founder in horses.
We know
that horses doing only light work do very well on high-forage
rations, and don’t need much grain. But, many horses need more
energy than forage alone can provide. Since grain starch in the
hindgut is such a problem, how do we choose an energy source? Do
all grains contribute equally to this problem, or are some better
than others?
The Digestive Tract at a Glance
Foregut – Stomach and Small Intestine – 1-6 hours – Horse
Enzymes digest sugar, starch, fat and protein.
Hindgut – Cecum and Colon – 18-36 hours – Bacterial Enzymes
digest plant fibers
(Click image to enlarge)
For More
Information e-mail at
AN_EquineHelp@admworld.com
or call toll free 7:30 AM to 4:30 PM
EQUINE
NUTRITION HELPLINE
1-800-680-8254 Central Time
ADM Alliance Nutrition, Inc.
1000 North 30th Street P.O. Box C1 Quincy, IL USA 62305-3155
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