VITAMIN A & CATTLE

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.