Is feeding pre and probiotics healthy for your horse?

Published : 2022-03-30 - Categories : Blog

Is feeding pre and probiotics healthy for your horse?

Nowadays a lot of horse owners feed their horses pre & probiotics and a lot of Companies add these to their bags of feed, supplements and balancers. But have you as a horse owner ever questioned if these are good for your horse? Is feeding pre & probiotics a healthy option or is it just another hype?

Lets start by explain what pre and probiotics are.

Pre- and probiotics are 2 different things. Both have a different way to help the intestinal flora. 

Prebiotics are raw materials that you feed that do not contain any live bacteria. They are substances that feed the bacteria in the intestine, so that they can grow in numbers.  So you help the existing bacteria grow in the intestine.

Probiotics are different, they do contain live bacteria.

Both pre and probiotics are promoted as a product that supports or helps to get and maintain a healthy intestinal flora. They `help`the fermentation of fibre. But is this really the case?


Lets find out!

The intestinal flora is super important and we know now that the microbiome is highly complex and reacts to a wide variety of influences.

The intestinal flora of a horse is actually still unknown to science. Recently, a new technique has been introduced that allows us to better identify and understand the intestinal flora. For humans! This research hasn’t been done on horses yet, Because the intestinal flora of horses is not at the top of the priority list in science.

A lot of vets will advice you to use probiotics after the use of antibiotics. But the administration of probiotics to support the intestinal flora after administration of antibiotics is controversial in human medicine. One study even showed that the administration of probiotics delayed rather than helped the restoration of a healthy intestinal flora. Which means it probably has the same effect on the horse as well. 

Companies are using the knowledge about the gut of humans for horses. But you can not compare them with each other! Us humans don’t eat grass, plants or bark.

Horses eat roughage, which consists mainly of cellulose. So they mainly need bacteria that have cellulose on their menu.

So why does your horse respond so well to probiotics? The most plausible explanation is that you are displacing one "bad" tribe of bacteria for another slightly less "bad" tribe. But you haven't addressed the cause, and the dysbiosis is still present in the gut. That is why you usually see a relapse when you stop feeding probiotics.

About Brewers yeast

Brewers yeast is commonly used as a fattening accelerator in live stock feed. A lot of studies have been done on the use of this product in livestock but not so much in horses. Studies show that feeding brewers yeast to pigs leads to faster weight gain and at the same time the diversity of the microbiome in the intestine decreased significantly.(1)

There are studies about feeding yeast to horses but the question is always what is the desired outcome of the studies? Most studies concerning yeast are financed by big yeast producing Companies. So they want a positive outcome!

Most studies show that yeast enhances the cellulose digestion in the hind gut. But when you read the study word by word ( devil is in the details ) then you see that they divided the group into 2.

1 group was fed hay and a lot of concentrate of Barley ( 2 kilo or so ) plus yeast

1 group was fed hay and 2 kilo of barley without the yeast

The group with the yeast performed better in the hind gut. But this is no surprise.

Besides this the yeast together with the barley produces alcohol and you don’t want this in the hind gut.

What they forgot in this study is 1 control group. So they would have needed 1 group just fed hay and 1 group hay and yeast. So 4 groups in total.

They did the same study in rabbits but with the 4 groups!. Rabbits and rhinos have a similar digestive system as horses. But there isn’t a lot of study done of rhinos. But there is on rabbits.

The outcome:

They found that the rabbits with the concentrates and yeast performed just as well as the rabbits with only hay, no yeast. So the message is that the yeast doesn’t actually enhances the fibre digestion within the rabbit/horse but it just neutralises the negative effects when feeding concentrates……


According to studies, the use of probiotics in foals led to more frequent visits to the veterinarian, since the intestinal flora of the foals was probably overgrown by the probiotics [2].


Overall, the results show that the use of probiotics in horses requires further research and that purely preventive administration without a therapeutic indication or even without consulting a competent therapist is not recommended. In the studies published to date, no long-term experiments with feeding brewer's yeast have been undertaken, neither have epigenetic changes been determined. So there is no data at all on the effects of long-term administration of probiotics over months or years. Many additional feeds for horses contain brewer's yeast without the horse's owner knowing about it, and it is not uncommon for several of these feeds to be given at the same time.

The fact that brewer's yeast is used in livestock as a fattening agent isn’t that positive for our horses, when you consider how many horses suffer from obesity even if they are fed hay alone. 

Our advice is to read about what you feed! Check out the supplements and bags of feed and then decide how you feel about the ingredients but also question why you feed pre and probiotics.  

So what can you feed to keep your horses gut healthy?

The answer = HAY HAY HAY HAY

Good quality hay, ad libitum. Hay is THE prebiotic that a horse needs. Because after all, what you feed grows. The cellulose digesting groups, should be able to dine like kings and queens every day. An additional thing that you can do is help optimize the conditions of the intestine. So that the right groups of microbes feel comfortable to live there.

@The Horse Therapist we can help you to get your horses gut healthy again. Because a healthy horse is a happy horse!


1.Okoro VM, Mbajiorgu EF, Mbajiorgu CA (2019). Yeast ( Saccharomyces cerevisiae ) and its effect on production indices of livestock and poultry - review. Comparative Clinical Pathology. 28:669-677.

2. Langner K, Vervuert I. Impact of nutrition and probiotics on the equine microbiota: current scientific knowledge and legal regulations. Veterinary practice Ausg G large animals farm animals. 2019 Feb;47(1):35-48

3. Own knowledge

4. Dr.Christina Fritz Sanoanimal


6.Ezema C, Eze DC (2012). Determination oft he effect of probiotic (Saccharomyces cerevisiae) on growth performance and hematological parameters of rabbits. Comparative Clinical Pathology. 21:73-76.


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