Brewer's yeast for horses: context, claims and dosage

Which yeast is on the declaration?

In the Catalogue of feed materials, number 12.1.5 is the category of inactivated yeasts, including brewer's yeast labelled accordingly. This describes a feed, not evidence of an effect. For a live yeast culture, on the other hand, the specific strain and the number of viable cells are essential for comparison with a study ¹².

• Note the exact product name and the composition.
• Is the yeast stated as inactivated or as a live strain?
• Is it a single feed material or a mix with other ingredients?
• Record the daily quantity fed and the corresponding unit.

What do the equine studies show?

The study by Medina and colleagues looks at microbial profiles and fermentation in the large intestine under high-fibre or high-starch feeding. It provides some evidence for the yeast preparation and trial ration studied there. It implies neither a benefit with every hay ration nor any statement about treating the horse's stomach ³.

In a more recent crossover study, eight adult Quarter Horses were studied with a specific live yeast. Apparent nutrient digestibility was measured. Such an endpoint is something different from fewer complaints, better skin or more muscle ⁴.

The review by Perricone and colleagues sets positive and absent findings side by side. Different strains, rations and trial conditions make general conclusions difficult. So read the exact research question of a study before applying its title to a product ².

How do you check claims about the gut, skin or muscles?

Three questions help with an advertising claim: was the same form of yeast studied? Does the trial ration roughly match your feeding? Was the promised benefit measured at all? A study of fermentation in the large intestine, for example, does not answer a question about a gastric ulcer ³.

For muscle building, the supply of usable protein and amino acids also needs to be considered. The crude protein value of an ingredient alone is not enough for this; the equine literature shows the limits of general protein surpluses ⁵.

• Protein and lysine in detail
• Stomach problems and feeding management

Which dosage and drawbacks should be considered?

A trial dose cannot be converted to another product simply on the basis of the horse's weight. Even the form of yeast may differ. So before adding anything, clarify the purpose, the product instructions and the conditions under which the published study took place ².

One drawback of an unplanned addition is the loss of overview of the overall supply. So note every change with date and quantity. Keep complaints and observations separate from your assumption about which product caused or improved them.

• What additional nutrient contribution does the quantity actually fed provide?
• Does the mix already contain other declared supplements that are given in parallel ⁶?
• Is there a documented feeding goal or only a general promise of effect?
• Which change do you want to observe, and which complaints need to be examined by your vet regardless?

• Critically check product information

Key takeaways

• First check which form of yeast is actually declared ¹.
• Yeast strain, live cell count and the ration studied are relevant to whether studies can be transferred ².
• An addition belongs in the overall balance with its actual daily quantity; more protein is no guarantee of muscle building ⁵.

Frequently asked questions