Stick to a white card with black text. It's easier on the eyes and won't require your logo to be in a square box. Overall a much cleaner look. Also, saying you are a rat breeder, and then saying you sell frozen and live asfs is redundant.
Lastly,
I also avoid making false claims (unless you really are the #1 exotics breeder in upstate NY) because they are both tacky, and a quick way to make yourself/your business look too "try hard".