Walk into any UK feed merchant and you will find a shelf of tubs promising better digestion. This guide compares four widely sold gut products that we have reviewed in detail, using only what each manufacturer publishes on its official product page, checked on 11 November 2026. We have not fed or tested any of them, and nothing here is a ranking based on results. The aim is to help you read the labels, understand the differences and choose a product that fits your horse and your feeding plan.
What counts as a horse probiotic
A probiotic is a live microorganism fed to support the gut. In UK equine products, a common choice is the live yeast Saccharomyces cerevisiae, and all four gut products in this guide declare it. Many products add a prebiotic, which is a fermentable carbohydrate that feeds gut microbes, and some now add postbiotics, which are inactivated microbes or their fermentation products. Our guide to equine probiotics explains how these work, and our guide to prebiotics and postbiotics covers the supporting ingredients.
Gut products also overlap with other categories. Some are mainly vitamin and mineral supplements with a yeast added, and some feed balancers contain yeast too. Knowing which category a product sits in tells you more about its purpose than the word probiotic on the tub.
Side-by-side comparison
The table below summarises what each manufacturer declares. Typical use reflects the manufacturer's own positioning, not our judgement of effectiveness.
| Product | Format | Key active ingredients as declared | Live yeast declared | Prebiotic included | Typical use |
|---|---|---|---|---|---|
| Protexin Gut Balancer | Powder | S. cerevisiae CNCM I-4407; Preplex (FOS and gum arabic); brewers' yeast | Yes | Yes (FOS, gum arabic) | Everyday gut balancer, 10g normal and 20g stress |
| Baileys Better Biome | Powder | S. cerevisiae MUCL39885; scFOS; inactivated yeast postbiotic | Yes | Yes (scFOS) | Broad hindgut support, 20g ponies and 40g horses |
| NAF In The Pink Powder | Powder | S. cerevisiae CNCM I-4407; FOS; vitamins, trace elements, amino acids | Yes | Yes (FOS) | Condition and micronutrient top-up with gut support, 16g to 32g |
| TopSpec Digestive Aid | Supplement mixed into damp feed | S. cerevisiae MUCL39885; MOS; vitamin B12; peppermint | Yes | Yes (MOS) | Digestion and appetite in working or stressed horses |
Two related products we reviewed sit outside this table. Protexin Acid Ease is a stomach-focused supplement with buffers and a live yeast, and TopSpec Comprehensive Feed Balancer is a feed balancer that includes a yeast and MOS but does not declare a strain or count on its product page.
Reading the yeast figures
Manufacturers declare live yeast in colony-forming units (CFU) per kg or per gram, which tells you little until you scale it to the daily amount. Using each label and the manufacturer's stated rate, our arithmetic gives these approximate daily figures.
| Product | Declared yeast count | Daily amount used | Approximate CFU per day |
|---|---|---|---|
| Protexin Gut Balancer | 1,000 billion per kg | 10g (normal use) | 10 billion |
| Baileys Better Biome | 2,500 billion per kg | 40g (horse) | 100 billion |
| NAF In The Pink Powder | 405 billion per kg | 24g (horse maintenance) | 9.7 billion |
| TopSpec Digestive Aid | 1,250 billion per kg | About 100g (implied, not stated) | About 125 billion |
Two cautions apply. First, a higher count does not mean a better product. Different strains are not interchangeable, and there is no agreed effective daily dose of yeast for horses. Second, the research is mixed: some studies found improved fibre digestibility with live yeast (Jouany and colleagues, 2008), while others in healthy horses found no change (Mackenthun and colleagues, 2013). A veterinary review concluded that evidence behind commercial equine probiotics is limited and product quality control is not tightly regulated (Schoster and colleagues, 2014).
How to choose
Start with the diet, not the tub
The hindgut runs on fibre. Before adding any product, check that your horse has enough forage, that changes are made gradually and that starchy meals are kept small. A supplement cannot make up for a diet that works against the gut. Forage should make up the bulk of the ration for almost every horse.
Match the product type to the job
If you want straightforward hindgut support with nothing else added, a dedicated gut balancer such as Protexin Gut Balancer or Baileys Better Biome is the natural category. If your horse also needs a vitamin and mineral top-up, a product like NAF In The Pink Powder covers both. If appetite is the main concern in a working horse, TopSpec Digestive Aid is designed around that. If the concern is the stomach rather than the hindgut, look at a gastric supplement instead, after speaking to your vet.
Check for double-ups
If your horse already has a feed balancer, adding a product with vitamins and trace elements may push some intakes higher than intended. Several balancers already include yeast, so a separate gut balancer may add little.
Check the base ingredients
Carriers vary: alfalfa meal in Protexin Gut Balancer, wheat feed and cooked maize in NAF Pink Powder, and grassmeal with sucrose in TopSpec Digestive Aid. These matter more for horses on restricted diets than the small quantities might suggest.
Check competition status
Protexin and NAF state NOPS accreditation or audit on their product pages. Baileys and TopSpec do not mention it on the pages we checked. BETA runs NOPS as a company scheme with an online web checker, and you should always check your governing body's rules too.
Work out cost per day
Tub prices are misleading because serving sizes range from 10g to around 100g. Divide the price by the weight in grams and multiply by the daily amount for your horse. Our full guide to choosing a horse supplement sets out this method with worked examples.
Editorial suggestions
These are suggestions based on our desk reviews of each manufacturer's published information. They are not test results and they do not replace advice from your vet or a qualified nutritionist.
Protexin Gut Balancer
A sensible choice if you want a simple, low-volume daily gut balancer with a declared yeast strain, no added vitamins or minerals and stated NOPS accreditation. The small serving suits fussy feeders.
Baileys Better Biome
A sensible choice if you like the idea of prebiotic, probiotic and postbiotic support in one product, particularly around antibiotics or box rest, and are happy to check NOPS status yourself.
NAF In The Pink Powder
A sensible choice if your horse is mainly forage fed with little hard feed and needs a small vitamin and mineral top-up as well as a live yeast. Less suitable if you already feed a balancer or avoid cereals.
TopSpec Digestive Aid
A sensible choice if you have a hard-working horse on a higher-concentrate diet with a fussy appetite, and you can confirm the daily rate with the manufacturer. Less suitable for horses on a tightly restricted sugar intake.
When a probiotic is not the answer
Gut products are designed to support healthy horses through change and stress. They are not a substitute for veterinary care, and loose droppings, poor appetite or weight loss can all have causes that no supplement will address. Keep notes on what you see and share them with your vet.
How we put this guide together
We selected products that are widely sold in the UK and whose ingredients and feeding information we could check on the manufacturer's official website. Every figure in this guide comes from those pages or from studies we have opened and cited. We do not accept payment for inclusion.