Components in the diet that are present in larger amounts will be listed as % . In a traditional feed, that would include crude fiber, fat, protein and the macrominerals Ca and P. It is optional to include more information on a feed tag. If the items are in large enough quantities, it makes sense to list them in %. Calcium and P are always listed in mins/max – it allows some flexibility as feedstuffs naturally have some variation, but the manufacturer has to provide the customer the assurance they fall within that range.

Components that are found in smaller quantities, the trace minerals are listed in ppm. Although most people still think in pounds, I always prefer to think about ppm in mg/kg. The reason I do so is that the requirements for these nutrients are always listed in mgs, so it just makes sense to get that answer right away.

IU are international units which are only used for vitamins. Because vitamins act as catalysts , their unit of measure is relative to the amount of activity they have. Each vitamin will actually have a different weight required for its international unit. Of course, some vitamins are actually listed in concentration by weight, however A, E and D will all be as IU.

Essentially, macronutrients will always be in %, micronutrients in ppm, and A, D, and E in IU.