We know antioxidants are important
for health, but few people really know what they are or what they do. Simply
put, antioxidants fight free radicals. So what are free radicals? Think back to
your high school science class. Somewhere between memorizing the periodic table
and blowing up chemistry beakers, you probably learned that cells are made up
of molecules that have an even number of paired electrons. Sometimes, however,
a molecule will end up with an odd, unpaired electron that makes it unstable
and reactive — a free radical.
The
free radical’s unpaired electron tries to “steal” an electron from other
molecules, setting up a chain reaction that continues to produce more and more
free radicals. The immune system may utilize free radicals to neutralize
viruses and bacteria, so in some cases free radicals can be helpful. But when
free radical production becomes excessive, damage to cells and body tissues can
occur.
Free
radical damage occurs with age, stress and environmental pollution. Unchecked,
free radicals in the system cause wear and tear on organs and body functions.
Antioxidants, such as vitamins A, E and C, and the mineral selenium, protect
the body against the destructive effects of free radicals by acting as free
radical scavengers. They donate one of their electrons to the free radicals,
stopping electron “stealing” reactions and helping to prevent cell and tissue
damage.
Vitamin
E is the most abundant fat-soluble antioxidant in the body. According to the
newly published National Research Council (NRC) Nutrient Requirement of Horses,
the vitamin E requirement for horses has not changed since 1989. (See sidebar.)
Some research suggests that extremely hardworking horses, such as those running
endurance races, might benefit from dietary vitamin E levels as high as 5,000
IU/day. This has not been well duplicated in other studies, but there are no
reported adverse effects to intakes in that range. Most research supports the
recommendation of 0.9 to 1.0 IU/lb of body weight for hardworking horses. But,
for horses exhibiting some muscle stiffness or elevated muscle enzymes, the
higher level may be of some benefit.
The
concentration of naturally occurring vitamin E varies considerably in typical
feeds for horses. Fresh forages and immature harvested forages contain the
highest concentrations of vitamin E, ranging from 15 to 50 IU/lb. Grains, such
as oats and corn, tend to have lower concentrations, from 10 to 15 IU/lb. A
diet of fresh pasture containing 50 IU/lb of vitamin E would well meet the requirements
of all horses, except possibly for those doing intense exercise that may
benefit from higher than normal recommended levels.
However,
vitamin E content declines over time in stored grains and hay. For example, vitamin
E in alfalfa stored for 12 weeks has been reported to decline 54% to 73%. So a
horse eating fresh alfalfa hay will usually consume adequate Vitamin E, but if
hay is very mature when it is cut, or is stored for an extended period, another
source of vitamin E may be necessary.
Vitamin
E intake will vary in typical, unfortified diets for horses. Therefore,
choosing a feed that is fortified with vitamin E will ensure adequate vitamin E
intake. Owners should be cautious when adding a vitamin E supplement to a
well-fortified concentrate, because most vitamin E supplements also contain
selenium. Too much selenium can be harmful, so contact your veterinarian or an
equine nutritionist for help in determining if your horses need additional vitamin
E and if the supplement you are using is safe with your current ration.
Vitamin E Requirements
1,100-pound mature
horse at maintenance .45 IU/lb or 500 IU/day
1,100-pound mature
horse with exercise .72-.90 IU/lb
depending on type of work
light work 792 IU/day
very intense work 990 IU/day
1,100-pound pregnant or
lactating mare .90 IU/lb or 990 IU/day
600-pound growing weanling .90 IU/lb or 540 IU/day
No comments:
Post a Comment