Concerns about Vitamin A deficiency in Midwest cow-calf herds this calving season
By Dr. Steve Ensley
There is concern for the 2019 spring calving season that vitamin A stores in pregnant beef cows will be low.
Common clinical signs of vitamin A deficiency can vary widely. Reduced feed intake, growth, night blindness, edema, diarrhea, low conception rates, abortions, stillborn, and weak calves. Calves born to cows deficient in vitamin A may have trouble mounting a normal immune response; which may place them at a higher risk for neonatal diarrhea or respiratory disease.
Without supplemental vitamin A, the vitamin status of cows will decrease over the winter and potentially become deficient. There is a wide difference in vitamin A bioavailability between mineral/vitamin supplements. Even if you are feeding a good quality mineral/vitamin supplement, animals may not be absorbing an adequate amount. Feed with elevated nitrate concentrations will also interfere with vitamin A absorption, another compounding factor during a drought.
Vitamin A concentration will decrease over time so storage of vitamin A supplements should be kept to a short time and not bought in the fall and kept until spring. Cows need 30,000 to 50,000 IU of vitamin A/hd/day. Injectable vitamin A is a quick method of returning the cow’s vitamin A status back to normal. If severely vitamin A deficient additional monthly injections may be needed.
Newborn calves obtain the majority of their vitamin A by ingestion of colostrum. Very little vitamin A is transferred across the placenta, unlike other minerals and vitamins. Calves born to vitamin A deficient cows may need a parenteral injection of vitamin A.
To diagnosis vitamin A deficiency in your client’s herd a 1 ml serum sample from COWS is required. An adequate number of cows in all the production classes of young heifers to older cows need to be sampled. Liver from deceased calves that have nursed can be used to evaluate vitamin A status. If a calf did not nurse, a liver sample will not be helpful to determine vitamin A stasis.
If low vitamin A status is a concern it should be addressed prior to calving to ensure the calves are healthy and able to respond to the environment stress in the spring. Now is a great time to assess vitamin A status in spring calving herds.