Why Does My Dog’s Poo Smell So Bad? The Dietary Fix

Part of our Complete Guide to Dog Digestive Health — everything you need to know about digestive problems in dogs and how to solve them through diet.

Particularly smelly dog poo is one of those problems that every owner notices immediately — and it is one of the most reliable signs that something is not right with your dog's diet or digestion. The smell is not random. It has specific causes, and addressing those causes through diet can make a dramatic and rapid difference.

What Makes Dog Poo Smell?

The primary compounds responsible for faecal odour are phenols and indoles — organic compounds produced when gut bacteria ferment undigested protein in the large intestine. When protein from a dog's food is not absorbed in the small intestine, it passes into the large intestine where bacteria break it down through fermentation. This produces phenols, indoles, hydrogen sulphide, skatole and other volatile compounds — and these are what cause the characteristic strong, pungent smell.

The more undigested protein that reaches the large intestine, the more fermentation, and the worse the smell.

What Causes Particularly Smelly Dog Poo?

• Poor protein digestibility in the food — the most common cause. Low-quality or hard-to-digest protein is not fully absorbed and ferments in the large intestine
• Overfeeding — feeding more than your dog can digest means excess protein reaches the large intestine
• Food intolerance or sensitivity — specific proteins or ingredients that the gut cannot process effectively
• Sudden food changes — disrupts the gut microbiome and causes temporary fermentation
• Eating inappropriate things — scavenging, eating grass or finding something outside
• GI infection — bacterial or parasitic infections can produce particularly offensive odour alongside loose stools

For persistent, offensive odour with no obvious one-off cause, the food is almost always the place to start.

When to See a Vet

Very smelly stools alongside blood, mucus, weight loss, lethargy or a sudden change in odour warrant a vet visit to rule out infection, parasites or gastrointestinal disease. If the smell is persistent and long-standing without other symptoms, a dietary trial is the sensible first step.

How Diet Directly Controls Faecal Odour

Protein digestibility is the primary lever. When more protein is absorbed in the small intestine, less reaches the large intestine to ferment — directly reducing the production of phenols and indoles that cause the smell.

Our Hydrolysed Digestive Care Dog Food achieved 95% protein digestibility at Ghent University Vet School — rated excellent by FEDIAF standards. Less undigested protein means dramatically less fermentation and significantly reduced faecal odour.

TruPet™ postbiotic — included in the recipe — was shown in a peer-reviewed study (Lin et al., 2019, Journal of Animal Science) to significantly reduce faecal phenol and indole concentrations in dogs. This is the only pet food postbiotic with direct, published evidence of faecal odour reduction.

What to Look for in Dog Food to Reduce Smelly Poo

• High protein digestibility — look for evidence, not claims. Clinical or feeding study data from an independent institution is the only reliable indicator
• Hydrolysed protein — already broken into small peptides, absorbed far more efficiently than intact protein
• Postbiotic with odour-reduction evidence — TruPet™ is the only ingredient with direct published evidence of faecal odour reduction in dogs
• Lignocellulose — supports stool firmness and reduces the loose, smelly stools that maximise odour
• Single protein source — simpler formulation reduces fermentation potential
• No artificial additives — some artificial preservatives and colourings may contribute to gut disruption

How Long Before You Notice a Difference?

Most owners notice a reduction in faecal odour within 1–2 weeks of transitioning to a highly digestible food. Always transition gradually over two weeks to allow the gut microbiome to adjust.

Frequently Asked Questions

Why does my dog's poo smell so bad?

The most common cause is poor protein digestibility. When protein is not absorbed in the small intestine, gut bacteria ferment it in the large intestine, producing phenols, indoles and other compounds that cause strong, pungent faecal odour. Switching to a food with higher protein digestibility directly reduces this fermentation.

What dog food reduces poo smell?

A hydrolysed dog food with high protein digestibility and a postbiotic with odour-reduction evidence. Our Hydrolysed Digestive Care Dog Food achieved 95% protein digestibility at Ghent University and includes TruPet™ — the only pet food postbiotic with published evidence of reducing faecal phenol and indole concentrations in dogs.

Is smelly dog poo a sign of illness?

Not necessarily, but it is a reliable sign that diet or digestion needs attention. If the smell is accompanied by blood, mucus, weight loss or lethargy, see your vet. If it is persistent and long-standing without other symptoms, a dietary trial is the right first step.

Can grain free dog food reduce poo smell?

Grain free removes common irritants and can help if grain sensitivity is the cause. For persistent odour, the issue is usually protein digestibility — a hydrolysed protein food goes further by reducing the amount of undigested protein that ferments in the large intestine.

How long does it take for dog food to reduce poo smell?

Most owners notice improvement within 1–2 weeks of full transition to a highly digestible food. Transition gradually over two weeks to avoid temporary disruption during the switch.

Looking for the full picture? Our Complete Guide to Dog Digestive Health covers causes, signs, dietary solutions and when to see a vet — all in one place.