Vitamin A plays a critical role in young calf health. Calves are born with very limited vitamin A stores because little transfers from the dam during gestation. Newly born calves rely heavily on colostrum for their supply of vitamin A, making the cow’s late-gestation diet critically important. Milk is a poor source, so calves depend on the colostrum for their Vitamin A supply for the first few months of life.
For most herds calving in late winter or spring, cows are fed stored or stockpiled forages during their last trimester. Recent research suggests that late gestation cows need 75,000 to 90,000 IU/d of vitamin A, but the amount of vitamin A in hay varies widely. Factors such as forage type, maturity at harvest, haying and storage conditions, as well as how long hay has been stored influence vitamin A levels. This can mean supplementation needs range from none at all to nearly the full requirement coming from a supplement.
Color Can Be a Clue
Greener hay generally contains more beta-carotene, and therefore more vitamin A, than bleached or weathered hay. It’s not a perfect measure, but it can give you a quick indication. To make this more useful, Nebraska Extension developed a set of hay samples with known vitamin A content so you can visually compare your hay to them.
Help Our Research – Bring Your Hay Samples
Nebraska Extension is working to develop a tool that would allow you to take a picture of your hay and get an estimate of the vitamin A content, but we need more samples. Bring a gallon sample of your hay to your local extension office (ask to send to Mary Drewnoski, UNL) and we’ll add it to our research analysis. Your sample will help us better serve beef producers in the future.
