Vitamin A Vitamin A needs special attention in beef cattle rations. This vitamin is found only in animals. Plants, however, are the natural source of vitamin A activity for animals. Large destruction of carotene in the components of cattle rations because of longer storage and heat treatments for drying and processing feeds. Use of younger calves by feedlots.
Young animals have lower body stores of vitamin A and are fed longer than older animals.
Stress of feeder cattle from hauling, handling, disease and parasites. Larger daily gains as a result of nutritional and genetic improvement. Vitamin A requirements are greater per unit of body weight. Higher nitrate content of forages, especially when grown under adverse weather conditions, with high nitrogen fertilizer applications. Higher nitrite and nitrate levels in livestock water.