Cattle grazing green grass get plenty of vitamin A, but wintertime makes it kind of tough.
By: Aaron Stalker, UNL Beef and Range Systems Specialist
Vitamin A is an important nutrient for beef cattle. While grazing green grass, cattle get plenty of vitamin A but during the winter vitamin A may be deficient and should be supplemented. Including vitamin A in a mineral mix is a common and effective method of ensuring cattle get the vitamin A they need.
Categorized as a fat soluble vitamin it has many vital functions, especially for health, reproduction, and growth. It plays a role in vision (in low light); normal kidney function; development of bones, teeth and nervous tissue; and maintains delicate tissues lining the respiratory, digestive and reproductive tracts, keeping them pliable and in good working order. Vitamin A deficiency thickens these tissues causing them to becoming more brittle and increases susceptibility to infection because the lining that would normally keep pathogens out is impacted. If the gut is hard and brittle it cannot absorb nutrients, resulting in poor gain. Vitamin A deficiency also impacts reproduction. If the bull doesn’t get enough vitamin A spermatogenesis is impaired. With low vitamin A, a cow will resorb or abort her fetus. Calves won’t grow well without vitamin A. Other symptoms include loss of appetite, rough hair coat, and reduced feed efficiency. Swelling of the legs and brisket, especially after working the animals, is also a deficiency symptom.
The best source of this vitamin is beta-carotene, a pigment in green plants that animals convert to vitamin A. If cattle are grazing green grass they will get plenty of vitamin A. Deficiencies can be an issue at times when the grass isn’t green such as winter or during drought. Drought can compound vitamin A deficiency because plants go dormant early in the year and it’s a long time before animals eat green grass again.
Producers should pay attention to vitamin A status of their cattle when feeding hay too. Hay storage can impact vitamin A levels. Carotenes deteriorate during storage and amounts vary tremendously in a bale. There is virtually no carotene in the outside of the bale where it’s brown and sun bleached. Inside, the forage may be green and preserved with plenty of carotene.
Ultraviolet light from the sun destroys vitamin A, while heat and humidity increase the rate at which it breaks down.
Fortunately, supplementing cattle with vitamin A is relatively easy and cost effective. Supplement vitamin A in the winter. There’s no need to supplement in the summer when grass is green. At the end of summer the liver will have high vitamin A concentrations. But by the end of the winter vitamin A deficiencies may exist without supplementation.
Ranchers can provide vitamin A in a mineral supplement or with an injection. Although minerals store very well, vitamins have a relatively short shelf life. Don’t store a mineral-vitamin mix for longer than one year. If a mineral-vitamin package is not fed within about a year the minerals are still good but vitamin activity can be reduced. In that case giving a vitamin A injection would allow a producer to meet requirements without wasting minerals. Oral pastes or drenches are also available.