Selenium yeast is a source of organic food-form selenium. It’s often referred to as organic selenium and is used in supplements and different types of pet food. It’s often the more favored form of selenium to be used in pet food due to its organic nature. While most might argue that selenium yeast is better for your feline, it’s also a fact that it’s harder to obtain. This is because the majority of cat food manufacturers offer sodium selenite as the needed source of your cat’s selenium intake. If you prefer selenium yeast in your cat’s food, try brands like Farmina, Nutro, and Ziwipeak.