Brewers Yeast is a great source of selenium, protein, and vitamin B complex. The B complex vitamins in brewer’s yeast include: B1 (thiamine), B2 (riboflavin), B3 (niacin), B5 (pantothenic acid), B6 (pyridoxine), B9 (folic acid), and H or B7 (biotin). This versatile yeast improves digestion of fiber, aids in muscle function and recovery and contributes to the horse’s general health at all stages of life.