as they grow. “Calves at pre-weaning,
weaning, and vaccination can be more
effectively supplemented with an
injectable along with free choice mineral.
Calves may not consume enough
selenium when only offered mineral
free choice,” advises Van Dyke.
Excessive amounts of selenium may
cause toxicosis. A chronic condition
occurs when animals ingest extra
selenium through forages over time.
Symptoms include long, cracked misshapen
hooves because selenium interferes
with proper hoof development.
There may be some hair loss, notably
the tail switch. Extreme amounts damage
the heart and lungs, causing weakness
and death within 24 to 48 hours.
“Dust off the bottle, read and follow
the directions when giving injectables,”
cautions Van Dyke.
DON’T OVERDO IT!
Jason Smith, Ph.D., Texas A&M
AgriLife Extension Service Beef
Specialist, advises ranchers to consider
selenium when running cattle on the
range or a forage-based environment.
“Forages may be too low in selenium
to meet the animals’ selenium
requirements,” Smith explains. “It’s
important the complete mineral
supplement has the correct level of
selenium to complement forages
and meet the animals’ requirements.”
Extensive operations may cover different
environments. One pasture’s mineral
program may not be identical to
the supplement plan on another part
of that ranch.
Selenium is a component of
enzymes, which drives numerous
metabolic reactions in the body. The
lack of this trace mineral inhibits metabolic
processes. The FDA and state
departments of agriculture also heavily
control selenium in animal feeds as
a feed additive, rather than a standard
feed ingredient. Smith warns that recommended
amounts of selenium for
cattle in one state may differ from
those in another to minimize the risk
of selenium deficiencies or toxicities.
Smith advises operators that many
trace mineral deficiencies look like
one another. Selenium deficiencies
may appear as decreased growth,
weight loss, poor reproduction performance,
or compromised immune
“Maybe we see calves that didn’t
respond to vaccinations, or there were
unexpected health outbreaks,” Smith
reveals. “Because of selenium’s role in
immune function, animal health is
one thing we observe. From a cow-calf
standpoint, health and reproduction
will see an impact from a selenium
deficiency. If we can prevent these
problems, we’ll be money ahead.
“Avoid or be conscious of feeding
several different feed supplements
that may all have some supplemental
selenium in them,” Smith advocates.
“We can run into over-supplementation,
potentially increasing the
risk of toxicity. We’ve seen situations
where people have lost sight of that,
and there have been consequences,
whether that be due to selenium or
another trace mineral. Remember
this concept if you’re using injectable
trace minerals. The body has some
ability to regulate the amount that’s
absorbed when feeding. When we
inject it, we take that capability away
from the animal. When we’re meeting
or slightly exceeding an animal’s
selenium requirements through the
diet, a dose of selenium through an
injectable could be problematic.”
Although the Great Plains has ample
selenium in forages and soils, this element
is subject to antagonists, such as
sulfur, iron, and molybdenum. These
elements limit the animals’ ability
to absorb selenium, and supplementation
becomes more critical. There
are also areas of the northern Great
Plains where water selenium content
(EDITOR:… interesting…) or accumulation
in plants can cause toxicity.
Dissolved minerals in water make
up a large portion of each animal’s
mineral consumption. A rancher
should test well water once a year if he
does not expect the supply to change
substantially. Check surface water
more often, even if it is well overflow
stored in a dirt tank or pond, especially
during drought. Water evaporates
during hot, dry spells, causing minerals
to become more concentrated.
Smith admits that producers ask
him more questions about selenium
than any other mineral. Information
about supplementing selenium and
other trace minerals is available from
extension beef specialists, veterinarians,
or beef nutritionists.
“Avoid or be conscious of
feeding several different
feed supplements that
may all have some
in them,” advises Jason
Smith, Ph.D., Texas
A&M AgriLife Extension
Service Beef Specialist.
“We can run into
potentially increasing the
risk of toxicity.”
NOVEMBER / DECEMBER 2020 I WORKING RANCH I 35