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Ask Dr. Dave

Robin from Wisconsin, writes:

Dear Dr. Dave,

I have mixed yeast in my feeds for 15 years. I believe the yeast is good for the hind gut to help digestion. I also feed probiotics which I understand is for replenishing the good bugs in the hind gut. What is the difference between the two? I use the probiotics during shows, after worming and vetting. Am I overloading the yeast? Is it alright to keep a horse on probiotics full-time?

Dear Robin,

Thank you for your great question about yeast and probiotics. It’s hard to comment on a practice that has been working for 15 years. Time certainly has tested your care, and it sounds like you and your horses are the winners!

However, let's look into the yeast and probiotic controversy. It’s generally accepted that any yeast that goes through any food processing is most likely killed. In order to actually feed your horse live yeast, you would have to provide him with the small blocks of live yeast which is used for bread making, or that found in many health food stores. Typically this is not done.

Probiotics are thought to be active in the small intestine, whereas yeast is thought to aid digestion in the hind gut; however, it is my personal opinion that they all work pretty much the same. We produce a vitamin-mineral supplement called Veterinarian's Choice, and we use Diamond V yeast as an ingredient. Veterinarian's Choice is to be fed daily, so the horses have a constant supplementation.

In actuality, most supplements are not the active live yeast but are yeast nutritional metabolites. These metabolites seem to support and strengthen the bacteria that are already present in the gut, not add new bacteria. I believe that most probiotics are similar – they are metabolites, not the actual bacteria. It has been shown that yeast/probiotics aid in the digestion of fiber by increasing the fermenting action of the bacteria resulting in better food utilization and increased energy production. This is especially important when feeding lower quality hay.

So, are you overloading your horse with yeast? I do not know for certainty, however I feel confident you are not harming your horses. You may, however, be spending more on your feeding program than necessary.

I would encourage you to continue daily supplementation with some form of yeast or probiotic. You are doing a great job. Don't try to fix it if it isn't broken. Thanks again for your good questions.

Good health for a good horse,

Dr. Dave