I've noticed a few a my duckling's feet look like they might be starting to turn inwards. I feed them Manna Pro duckling starter and haven't really had any niacin deficiency problems with the other ducklings I've raised but I wanted to start giving some brewers yeast to my current ones just in case. I looked in Walmart and TSO and all I could find were these tablets for dogs. Are these okay to give to ducklings? If so, how much? Also, I have one chick that I've raised with the ducklings. Would it be okay if it gets brewers yeast?