Why vitamin A matters in livestock production

Vitamin A is an essential fat-soluble micronutrient in the diet of ruminants, playing a key role in immune function, reproduction, mucosal health, bone development, and vision.

- Dr Johann Stadler. Antrovet Animal Health

It is primarily stored in the liver and must be obtained through dietary sources, as cattle and sheep cannot synthesise it on their own. Instead, they rely on beta-carotene - a plant pigment found in green forage - which is converted into active vitamin A (retinol) in the small intestine.

Ruminants grazing on lush green pastures, particularly in spring and early summer, typically ingest adequate beta-carotene. However, during winter or periods of drought, forage loses its greenness and contains little to no beta-carotene. This significantly increases the risk of vitamin A deficiency, especially if animals depend on dry hay or grain-based diets.

While vitamin A stores in the liver can temporarily compensate for dietary deficiencies, these reserves don't last for ever. Once depleted, clinical signs of deficiency start to present.

When to supplement

Start with supplementation two months after the grass has begun to yellow.

Administer injectable products every two months until lush green pasture becomes available again. Animals on high-concentrate diets in feedlots have a reduced ability to convert betacarotene in the small intestine, making supplementation necessary. The demand for vitamin A increases significantly during late gestation, and adequate levels help reduce the risk of mastitis, pneumonia, retained placenta, and birth defects.