Yeast is a type of unicellular fungus that has various applications in the animal health industry. It is commonly used as a feed additive to improve digestion and nutrient absorption in animals. Yeast is a rich source of B vitamins, amino acids, and enzymes, which support the microbial balance in the gut and aid in the breakdown of complex nutrients. Additionally, yeast products like yeast cell walls are used to enhance immune function in animals.