Darn near every product has a label with the ingrediants and the percent of active ingrediant. Feed additives list the ingredients in order of the percent of product in the mix. The first one listed is the one that is the highest percent.
Using that, you can compart products.
FYI: Look at labels of dog/cat food. Some list "corn gluten" as the first ingredient (meaning it is the highest ingredient by percent), some list poultry, lamb as the first ingredient. Pretty interesting!