Like for human, your guess is as good as any idiot out there, the best would probably make his food like yours, home made and try the best you can/know in balancing all the ingredients and of course fresh, if still possible without gmo's, antibiotics and if possible avoid all the pollutants in/from this toxic world or just follow the crowd, buy the most expensive and hope for the best. All starts with the right diet but nobody really cares about that, as there is way more money in drugs and in making the world sinker versus healthier.