By Heidi Smith, DVM
With the onset of winter, one of the biggest concerns in keeping horses healthy is ensuring that they can generate sufficient body heat to stay warm during cold weather. Obviously, it takes more calories to stay warm in the cold, but what is the best way to provide those calories? The following is a brief review of how equine digestion works and a simple solution that has worked well for us.
Although the horse is a monogastric (one stomach), his digestive
tract differs a lot from that of a dog or a human. His stomach
is quite small relative to his body size (only about twice the
size of a human's stomach) and the remainder of his digestive
tract has some unique adaptations that enable the horse to be
an efficient grazing animal. The most noticeable adaptation to
forage digestion is his large colon; it fills the majority of
the horse's large abdominal cavity. It is here and in the adjacent
cecum that a large amount of forage digestion takes place.
Bacteria in the large colon and cecum have the capability of
breaking down the cellulose in forages that cannot be processed
in the small intestine. When the chemical bonds that hold the
cellulose together are broken, heat is released. This is a very
useful byproduct in cold weather when the horse is trying to
stay warm. Further processing of the cellulose by the bacteria
yields compounds called volatile fatty acids. These compounds
are absorbed into the bloodstream and can be utilized directly
in the Krebs cycle (the metabolic process in the cells that releases
energy) just as blood glucose is.
It is now understood that in horses that perform aerobic work
(such as endurance horses or ranch horses), the volatile fatty
acids from forage metabolism actually provide a very large percentage
of the horse's energy needs. Furthermore, since the digestive
process in the large colon and cecum is constant and ongoing,
the energy provided by volatile fatty acids is very steady--ideal
for keeping a horse warm in cold weather.
Another source of heat is protein. The chemical bonds in protein
are especially strong, and release a large amount of heat when
broken in the digestive process. Hence high protein feeds are
very appropriate in winter weather, but a detriment in hot summer
weather in horses working hard and having to get rid of excess
body heat. Extra protein is further metabolized into useable
energy which can be used to produce more heat.
The ideal feeds for winter, then, are forages, and particularly
those with protein levels higher than maintenance levels. In
other words, high quality hay is the ideal winter feed, and alfalfa
becomes a good choice as the weather gets colder.
The next problem is how to best get sufficient amounts of hay
into a horse to provide his heat needs. The horse's small stomach
makes meal feeding less than ideal. In herd situations, dominant
or greedy individuals will often eat more than their share of
meal-fed hay, depriving less aggressive or slower-eating individuals
of adequate feed. Furthermore, if the horse rapidly consumes
his share, his digestive tract will have active periods and slow
periods, as the reflex stimulation of a full stomach causes activity
further down the tract. This is not conducive to a steady state
of digestion in the large colon and cecum.
We've addressed this issue in our own horses for the past several
years by free-feeding hay in large bales. In nature, horses graze
off and on continually, taking small meals at frequent intervals.
Free-feeding approximates their natural grazing habits. It has
been our experience that when meal-fed horses are initially offered
free-feeding, they will only overeat for about 4 or 5 days. After
that, they begin to self-regulate. We've compared hay consumption
between free-fed groups and meal-fed groups, and have found that
after the initial week or so, we actually feed slightly less
tonnage when free-feeding. Some of this can be attributed to
less waste, as the feed is all in one area. But it also illustrates
that the free-fed horses will regulate their feed intake once
they are used to the system.
We've found with free-feeding that there is no meal-time frenzy
as there is in groups being fed hay at twice or three times daily
intervals. All horses can go to the big bales whenever they are
hungry, and the aggressive ones do not tend to pick on the timid
ones since there is no competition for feed. The best benefit,
though, has been the condition of our horses. We free-feed horses
ranging in age from weanlings to geriatrics, and find that they
all maintain weight well. Slower-eating horses can keep up with
their herd mates, older horses are not pushed out by those in
the prime of life, and youngsters can also get their needs met.
We currently free-feed three different social groups. We maintain
a bachelor herd of young stallions, a group of dry mares, and
a group of nursing mares, youngsters, and geriatrics. The latter
group gets alfalfa or alfalfa-mix hay at all times to meet the
protein (particularly lysine) needs of the younger horses and
nursing mares. The other two groups get good grass hay (timothy
or orchard grass) and only get alfalfa when the weather is fairly
cold. All three groups regulate their intake well, with quantity
of hay consumed going up noticeably when the weather is severe.
In winter, our free-fed horses maintain weight well and come
through severe cold snaps without shivering or showing adverse
effects from the cold. They seem to regulate their intake relative
to the weather far better than we can--when meal-feeding, it
is guesswork to estimate a horse's particular needs on a cold
night and adjust his feed by an extra flake or two.
After five years of free-feeding, we have also noticed better
overall dental health in our horses. We attribute this to the
fact that free-feeding more closely approximates natural grazing
and browsing, and hence provides wear on the teeth more in keeping
with their normal eruption rates.
Another added benefit has been a decrease in the labor required
to feed a large number of horses. It is a simple matter to have
the large bales loaded in the back of a pickup, and to drive
out into the pasture and pull them off, using a tree, fence post,
or second vehicle as an anchor. Compared to the usual system
of having to meal-feed twice daily, making sure that flakes are
sufficiently separated to prevent fighting, this has proven for
us to be a much more time-efficient system.
 |
|