Check Your Hay for Vitamin A Levels This Winter

By Scout Nelson

Vitamin A plays a vital role in the health of newborn calves, yet calves are born with very limited reserves.

Because little vitamin A transfers from the dam during pregnancy, colostrum becomes the primary source for young calves in the first months of life. Milk contains only small amounts, making the late-gestation diet of the cow critically important.

Most herds calve in late winter or spring, when cows are usually fed stored or stockpiled forages. Research shows that cows in late gestation require 75,000 to 90,000 IU of vitamin A per day.

However, the amount in hay varies significantly depending on forage type, maturity at harvest, storage conditions, and length of storage. This means supplementation needs can range widely, from none at all to nearly the full requirement.

Hay color can provide a useful clue. Generally, greener hay contains more beta-carotene, which is converted into vitamin A, while bleached or weathered hay has lower levels. Though not exact, this simple check can help farmers make quick decisions about nutrition.

To make this method more accurate, Nebraska Extension has developed reference hay samples with known vitamin A content. These allow farmers to visually compare their own hay with samples to estimate levels more effectively.

Farmers will have the chance to view these reference samples at upcoming Nebraska Extension events, including the GSL Open House on August 20, 2025, and Husker Harvest Days from September 9 to 11 at the “Big Red Building.”

Attendees can compare hay samples, get advice on whether supplementation may be needed in winter feeding programs, and speak directly with experts for nutritional guidance.

These tools and events aim to help producers maintain healthy cows and calves while ensuring that feed programs meet critical vitamin A requirements during winter months.

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