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Seniors relaxing
Continued...
SENIOR HORSE PHYSIOLOGY
Not too long ago, in some breed registries, it
was an automatic “assumed dead and remove
from registry” standard when a horse
reached the age of 25. To reinstate your
senior horse back into the registry, it was a
compilation of paperwork and pictures proving
the horse’s existence. At that time, senior
horses over 20 were far and few between.
Now, research indicates that senior horses
make up to 17% of the entire equine population.
Not just a few anymore.
It is generally accepted that the aging process begins to
show signs after the 18-20 year mark. It includes, changes
in eye sight, skin, bones, internal organ functioning, mobility,
hormonal functions, thermoregulation, digestion, and
immune function to name a few. Luckily, for the horse, it
is mostly a slow process. However, in some instances, the
aging process can be easily overlooked by the owner. In
the wild, a less than spry horse is generally singled out by
a predator and the rule of nature presides. In captivity,
this is eliminated and it is up to the human to oversee the
process. Only in the past 20 years or so has research been
done to study senior horses as a group.
As in other mammals, eyesight and perception can diminish
with age. Cataracts, corneal scars from past injuries and
changes in the internal eye itself (behind the cornea) can
present from ghost like figures, blank areas where blackness
is observed and up to total blindness. Since the horse is a
flight animal (as compared to a predator), vision problems
can easily lead to the horse being unsure, hesitant, stressed
and can even result in negative behavioral problems.
With age, the heart loses some of its function ability,
therefore decreasing the horses ability to thermoregulate.
Basically, the heart has to work harder in order to get
blood to the internal organs as well as the skin. Both heat
and cold conditions are not met with full capacity. Drastic
temperature changes and weather conditions cannot be
easily handled by an aging horse. Fiber production in the
hindgut produces heat. If there is a reduction in processed
fiber, there is a lessened ability to produce warmth. Fat
(used as insulation) reduction covering the body allows for
the increase of cold sensitivity. Hormone production may
also be altered which in turn regulates the body’s ability to
adjust to heat and cold.
The effectiveness of the intestine to allow nutrients to pass
through and be absorbed decreases with age. Research
indicates that absorption of phosphorus, protein and vitamins
are majorly decreased in the aging process. Additionally,
production of the enzymes necessary for the digestion
of starch are decreased allowing for a buildup of starch in
the hindgut. Due to the fermentation process, the hindgut
may become more acidic which can then lead to laminitis
and colic.
Another factor in the aging process is the connection between
the teeth and food processing. As the horse ages,
so does the tooth structure, gums and a host of other dental
problems If the teeth fail to thoroughly chew, the size of
the food particles are too large for the gut to handle thus
resulting in undigested food. Additionally, tooth problems
also make the horse more prone to choke. The amount of
saliva put forth for chewing is directly related to how long
chewing is performed. Tooth problems shorten that chewing
length significantly. Without thorough mastication, food
can get trapped in the esophagus because of the decrease
in lubrication (saliva).
Some of the aging changes are listed below.
Exercise is important in the aging process. Exercise can
actually slow down the aging process of many systems. Not
Olympic training exercise, but moderate activity has proven
to extend a horse’ s useful life. System slow down can
result from insufficiencies. For example, the heart (a muscle)
needs to pump efficiently in order to supply oxygen to
AGING – WHEN DO
THE GOLDEN YEARS BEGIN?
THE BASICS -AGING PHYSIOLOGY
– A CASCADE EFFECT
TABLE 1
SOME PHYSIOLOGICAL CHANGES
IN AGING HORSES
Arthritis
Anemia
Dementia
Hyperinsulinemia
Decrease digestibility of food
Inability for nutrient absorption
Decrease in intestinal mobility
Decrease in liver and kidney function
Increase in common geriatric tumors (e.g. thyroid,
melanoma, mesenteric, and pituitary)
Immunological inefficiency
Respiratory inefficiency
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