Like we need a variation in our diet so does every other animal and insect to. From bees, chickens, salmons, cows, and pigs. The idea is that we take advice from the animals own decision making which I call their free will. It’s simple. Perhaps instead of using one type of food. Why not have different kinds and let the animals choose themselves. My guess is if you do this their immune system would improve.
So my idea is. Because the animals have a brain they also have an evolved free will that naturally guides them. If were are smart we would let this system do what it does best and let the animal choose their own food.