I would assume that the level in something essential is not high enough, especially since other proteins indicate that they are balanced for cats. NV has gone through feeding trials in addition to the normal chemical testing to ensure their foods are balance.
You might want to call them and see if they can tell you what is low, then supplement yourself if you really want to feed bison. If you use bison in rotation with other proteins then I wouldn't be too concerned as long as it doesn't make up a significant part of the diet.
You might want to call them and see if they can tell you what is low, then supplement yourself if you really want to feed bison. If you use bison in rotation with other proteins then I wouldn't be too concerned as long as it doesn't make up a significant part of the diet.