Horsepower Vitamin SupplementLike minerals, adequate vitamin intake is essential to a well balanced diet, and again, like minerals, a horse's daily requirement for vitamins can vary with age, level of exercise, reproductive status, health and stress. A deficiency of Vitamin A can lead to night vision blindness interestingly, beta carotene (which the body turns into Vitamin A) is readily found in carrots, so there is some truth to that old wives' tale about carrots helping you see