Vitamin
A is a required component in the beef cattle industry.
Vitamin
A, as a final product does not occur in green plant material. It occurs in the forms of carotenes and carotenoids in green plant
matter. Carotene is rapidly destroyed
by sunlight and air, especially at higher temperatures (hot summer
conditions/dry, bleached pastures). The carotene in green
matter is converted into Vitamin A by animals in their small intestines. The
Vitamin A is than later stored in the animal’s liver for up to 3 months before
it is eventually consumed and runs out. The dry yellow grass cannot contain carotene/Vitamin
A. Consequently, it is recommended you
vaccinate with Vitamin A during the dry months. The following are Vitamin A deficiency consequences.
1. Vitamin A is associated with the maintenance of the protective
mucous membranes of the respiratory and
digestive tracts
resulting in the prevention of diarrhea and pneumonia. It is thought that a deficiency in vitamin A causes damage to these membranes which
allows bacteria and viruses an
opportunity for invasion.
2. It also helps with a compound in the eye needed for sight when an animal adapts
from light to dark. One of
the first easily detected signs of vitamin A deficiency in
cattle is night blindness. An easy way to check for this condition is to place an
obstacle in
the
pathway of cattle and
notice
if they stumble over it at twilight.
3. Vitamin A is also
essential for
proper kidney function and normal development of
bones, teeth and
nerve tissue.
4. Signs of vitamin A deficiency in breeding herds include lowered
fertility and calving percentage. Pregnant heifers
and cows are especially sensitive to Vitamin A deprivation as this limits the
development of the foetus, especially in the last trimester where the foetus grows
the most. This results to under
developed foetus and stillbirth.
5. Lameness stiffness tiredness, lose of appetite, rough hair coat, slowed grains and reduced feed efficiency, pneumonia (especially in calves)and watery eyes are additional symptoms.
Beef cattle requirements for vitamin A are 2200 IU/Kg dry feed for beef feedlot cattle, 2800 IU/Kg dry feed for pregnant beef heifers and cows, and
3900 IU/Kg dry feed for lactating cows and
breeding bulls.
It is advisable to supply incoming feeders or other cattle under extreme stress conditions with
500 000 to 1 million
IU of vitamin A.
