Brewers Yeast for Horses: Beneficial or Bullshit?

What’s the deal with brewers yeast for horses?

It seems that it’s a good source of natural B vitamins, however any claims that it assists with digestion & fermentation should be taken with a grain of salt.

Brewers Yeast for Horses

What is it?

As the name suggests, brewer’s yeast is one of the by products derived from brewing beer.

Brewer’s yeast contains a relatively high concentration of high quality protein, and is also a good source of fat, water-soluble B vitamins (exception is B12) and phosphorus.

Brewer’ Yeast does not contain ‘live’ cultures.

The claims

Like most horse supplements, product listings for Brewers Yeast often have a lengthy list of purported benefits including:

  • Improves appetite
  • Calms nervous & anxious horses
  • Acts an an immune system booster
  • Works as a digestive aid

The evidence:

Despite articles vaguely referring to ‘studies’, it seems that the benefits of brewer’s yeast for horses are mostly anecdotal.

‘Seeming to give the horse a natural lift, these supplements, though unproven by science, have a great following among experienced horse people’ 

Vitamin B1 (thiamine) has historically been used as a supplement to calm nervous horses. This is because thiamine plays a vital role in carbohydrate metabolism and nerve transmission.

If a horse has a high grain diet and stressful lifestyle,  they may develop a thiamine deficiency. However,  thiamine is well supplied in green forage and deficiencies are rare.

The bullshit detector

Brewers yeast cultures enhance the activity of good (beneficial) hind-gut activity in your horse


Brewers yeast is non-active. In other words, the cultures are dead. They do not assist with repopulating a healthy bacteria population in the horse’s gut.

The bottom line

There’s no disputing that horses find brewers yeast delicious. Therefore it stands to reason that it will help stabilise a horse’s appetite when it’s added to feed.

As a calming supplement, it seems that there’s strong anecdotal evidence to support this. However, from a scientific viewpoint it seems that brewers yeast will only be effectinve with horses that have an existing vitamin B deficiency.

There’s little evidence to support claims that brewers yeast will boost a horse’s immune system.

Similarly, claims that brewers yeast acts as a digestive aid seem to be based on the (incorrect) assumption that brewers yeast is a source of live bacteria.


Further reading:

‘B Vitamins in Horse Nutrition’



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