Understanding feed and supplement labels can be difficult. Work with a qualified equine nutritionist to determine what feed or supplement will work best for your horse. | Photo: Erica Larson

A: Kudos to you for looking at labels and comparing products, and I’m sorry that it hasn’t been as straight forward to decipher as perhaps you’d hoped.

Calcium is an example of a macromineral, meaning that it’s found in body tissues at concentrations greater than 100 ppm (there’s that unit again!). Other macrominerals you might see listed on feed or supplement labels include phosphorous, magnesium, sodium, chloride, potassium, and sulfur. Copper and zinc are trace or microminerals and found in body tissues in amounts less than 100 ppm. Other trace minerals commonly considered in the horse’s diet include cobalt, iron, iodine, manganese, and selenium.

So what is ppm? This unit stands for parts per million and is a measure of concentration equivalent to 1 milligram per kilogram. So if there’s 50 ppm of copper in a feed that means that, if you feed 1 kilogram (which is equal to 2.2 pounds), you would be providing your horse with 50 mg of copper