– nature’s own protection
Alpha tocopherol is preferentially
absorbed by people and has the
greatest body of research. It is also
the form that is thought to be the
most important to horses although
there is some new data that suggests
gamma tocopherol may also have
previously unrecognized benefits.
When we talk about a horse’s vitamin
E requirement we are referring to the
requirement for alpha-tocopherol.
Alpha tocopherol comes in different
forms. The natural d-alpha
tocopherol and a synthetic form
known as dl-alpha tocopherol.
Research in horses has shown
that the natural form has greater
bioavailability than the synthetic
form in equine diets. This means that
greater amounts of synthetic vitamin
E needs to be fed each day to get
the same benefit as a lessor amount
of natural vitamin E will achieve.
HYGAIN uses natural vitamin E
to insure your horse is able to get
the maximum benefit from dietary
vitamin E.
Research in rats has shown that
vitamin E is vital for membrane
repair in working muscles. As
muscles contract damage occurs
to the membranes around the
muscle cells. In healthy rats with
adequate dietary vitamin E, damage
to membranes was fixed in minutes
but this was not the case in rats fed
vitamin E deficient diets. These rats
had lower running ability and took
more frequent rest breaks.
Working muscles utilise more
oxygen, and therefore produce
more free radicals. To avoid damage
to muscle cells during exercise,
adequate levels of antioxidants
must be available to counter all the
extra free radicals that are being
generated. This is why, as a horse’s
workload increases, his requirement
for vitamin E goes up, too. Signs of
oxidative damage in working horses
include muscle soreness and stiffness
and slower-than-expected recovery
from intense exercise.
While the level of vitamin E provided
in commercial feed is enough to meet
requirements for most horses when
fed properly, individual variation
between horses in their ability to
utilise dietary vitamin E is great. For
this reason it is generally advised
that performance horses have their
vitamin E levels checked in order
to determine whether additional
vitamin E supplementation is
required.
Selenium
Selenium is often thought of in
combination with vitamin E as it is a
potent antioxidant that plays a vital
role as a component of the enzyme
that turns harmful peroxides
(single oxygen to oxygen bonds)
in to harmless alcohols before it
can do significant damage to cell
membranes. Vitamin E and selenium
work together to protect muscle
tissue, with Vitamin E helping to
reduce the formation of peroxides
in the cell membrane and selenium
removing peroxides that do occur
from the fluid surrounding cells.
When one or other of these nutrients
is deficient the other must work
harder to protect cells. Additionally,
selenium plays a number of other
important roles in the body although
they are not antioxidant in nature.
These include roles in thyroid
function and immune function. Many
of the selenium deficiency issues that
used to be seen in horses are less
common today due to the practice of
adding selenium to commercial feeds
fed to horses. It is still advisable to
check your horse’s selenium levels
especially if you are in a selenium
deficient area and feeding forages low
in selenium.
Additionally, not all forms of
selenium are as bioavailable as
others which may impact tissue
levels. The inorganic forms sodium
selenite and sodium selenate are
less bioavailable than the organic
selenium yeast. Not only is selenium
yeast absorbed better from the
digestive tract it is also taken up in to
muscle tissue more readily than the
inorganic forms. Hygain uses organic
selenium in our feed formulations.
Vitamin C
Less commonly considered
antioxidants in the equine diet are
vitamin A or beta-carotene and
vitamin C. Unlike humans, horses
actually make vitamin C in their
liver and therefore do not have a
dietary requirement. Limited data
suggests that there may be a benefit
to supplementing senior horses
with additional vitamin C as well as
horses with soft tissue injuries that
need to build collagen. Additional
vitamin C may also be beneficial for
horses suffering from allergies and
r espiratory conditions due to its role
in antihistamine control.
Care should be taken when removing
a supplemental source of vitamin C
from the ration to do so gradually.
Supplementation may cause the
horse to produce less vitamin C of his
own leaving him with a short fall if
the supplemental source is removed
suddenly.
Vitamin A
Vitamin A is rarely considered by
most horse owners due to the fact
that the precursor beta-carotene is
abundant in fresh pasture and other
green forage. However, levels of beta-
carotene drop quite dramatically
(almost 50 percent after a year) in
stored forages which could result in
a shortfall in horses fed aged forages.
Critical for normal immune function,
vision, reproductive health, and
bone health among other functions,
vitamin A is routinely added to
commercial feeds and supplements.
Like vitamin E, it is a fat-soluble
vitamin which means that it can
be stored in the liver for months
at a time. Vitamin A does not in
fact exist in plants, they contain
carotenes which the horse absorbs
and converts to vitamin A as needed.
Care must be taken when combining
feeds and supplements that provide
vitamin A because in its vitamin A
form the horse has less ability to
regulate how much is absorbed and
it is possible to create a vitamin A
toxicity.
Because free radicals can engage in
so many different types of chemical
reactions, it is good to have a
wide array of antioxidants in the
diet to counter them. Research
is indicating potential benefits of
other antioxidant compounds such
as supplementing Resveratrol to
horses with joint pain. However,
data in horses is lacking for many
antioxidants touted as beneficial to
humans and results cannot always be
accurately extrapolated to determine
expected outcomes in horses.
For now, insure that you are
correctly feeding commercial feeds
that provide the most bioavailable
sources of key antioxidants at
levels balanced to meet, but not
excessively exceed, your horse’s
daily requirement. If you believe that
you are seeing conditions that may
be linked to an antioxidant deficiency
talk with your veterinarian about
testing your horse’s levels and then
adjust the diet accordingly.
Printed with permission of HYGAIN Feeds