I have a few horses that get a variety of supplements and I like to premeasure and put them into containers so that the barn manager doesn’t have to weight them out each time (and they are supplements not available through SmartPak). Is there a rule of thumb of some guidance regarding which kinds of supplements should or should not be combined and stored together for a period of a week or so? – CP

Dear CP,
Unfortunately, I have not been able to find any sort of guidelines for which supplements or ingredients should not be mixed together for a length of time before feeding. After speaking with several research scientists and nutritionists however, I did learn that it’s a complicated issue and it’s probably best NOT to mix supplements.

For example, products containing unstabilized fats should not be combined with products containing antioxidants like Vitamin E, Vitamin C or Vitamin A because the fats rapidly degrade the antioxidants, essentially using them as preservatives. Then they are not present in the amounts listed on the label anymore and the horse doesn’t get them as vitamins or antioxidants or whatever their intended use. Some inorganic minerals can have similar chemical reactions with certain other ingredients and reduce them to meaningless levels.

What I learned from this brief foray into the biochemistry of nutrition is that the specific ingredient and the chemical form it’s in have a lot to do with whether it will react with other nutrients. Therefore, it’s probably best to trust manufacturers to know which ingredients can be combined with which other ingredients in their own product, and that combining two or more different products, even from the same manufacturer, is probably not a good thing.