The trace mineral content of most feeds and supplements is provided in terms of parts per million (ppm). A ppm is the same as mg/kg (1 mg is a millionth of a kg).
To do calculations, you need to convert lb or oz to kg using the following conversions:
- 1 lb equals 0.454 kg
- 1 oz equals 0.0284 kg
Example #1: Your hay contains 140 ppm of iron. How much iron is in 20 lbs of hay?
Step 1: 20 lb X 0.454 kg/lb = 9.08 kg
Step 2: 9.08 kg X 140 mg/kg = 1271 mg of iron
Example #2: Your supplement contains 12 ppm of selenium in each ounce and you are feeding 2 ounces per day. How much selenium are you feeding?
Step 1: 2 X .0284 kg/oz = 0.057 kg
Step 2: 0.057 kg X 12 mg/kg = 0.68 mg of selenium
Formulas to remember:
- Convert lb or oz to kg: lb X 0.454 = kg; oz X 0.0284 = kg
- Calculate to find mg: kg X ppm (or mg/kg) = mg
About Dr. Juliet M. Getty
Juliet M. Getty, Ph.D. is an internationally respected, independent equine nutritionist who believes that optimizing horse health comes from understanding how the horse’s physiology and instincts determine the correct feeding and nutrition practices. She is available for private consultations and speaking engagements. Hear Dr. Getty address issues in horse nutrition at the Kirkland House Foundation in Delta, British Columbia, sponsored by “Hay…Girl!” on May 2, 2015. For more information, contact Pam Janssen at precioushaygirl@gmail.com or call 604-961-7265.
Dr. Getty’s comprehensive resource book, Feed Your Horse Like a Horse, is available at Dr. Getty’s website, www.gettyequinenutrition.com, as well as from Amazon (www.Amazon.com) and other online book retailers. The seven separate volumes in Dr. Getty’s topic-centered “Spotlight on Equine Nutrition” series are also available at her website (where Dr. Getty offers special package pricing) and from Amazon (in print and Kindle versions) and from other online retailers. Dr. Getty’s books make ideal gifts for horse-loving friends.
Dr. Getty’s website, www.gettyequinenutrition.com, offers a generous stock of free, useful information for the horseperson. Sign up for her free monthly newsletter, Forage for Thought; browse her library of reference articles; search her nutrition forum; and purchase recordings of her educational teleseminars. Reach Dr. Getty at gettyequinenutrition@gmail.com.
