Dog Gut Health: Digestibility, Stools and Switching Food

Yes, and this is the answer with the best evidence behind it.

In a 28-day trial of 56 adult dogs, apparent total tract digestibility of protein ran between 87.9% and 89.6% and fat between 96.0% and 96.7%, at larvae meal inclusion levels of 5%, 10% and 20% — none significantly different from a control diet containing no insect protein (Freel, McComb & Koutsos, Journal of Animal Science, 2021). Total tract digestibility refers to how much of the food or a nutrient is digested and absorbed by the dog rather than passed through in its stools.

A separate cross-over trial in six beagles compared the same base diet made with either poultry meal or black soldier fly larvae meal. Protein digestibility was higher on the insect diet (82.3% vs 80.5%) and fat digestibility higher too (94.5% vs 91.6%) (Abd El-Wahab et al., Animals, 2021).

Note the comparator in that second trial: poultry meal, a rendered by-product, not chicken breast. It is a fair comparison against what is actually in most dry dog food.

Partly, and the picture is mixed so we'd prefer to set it out properly.

In the six-dog cross-over trial, faecal consistency scored 2.25 on the insect diet against 2.71 on poultry meal, on a five-point scale where 2 is the optimum — closer to ideal on the insect diet, and the authors describe that as a clearly positive effect. But faecal water content was higher on the insect diet, and total wet output was higher too. The authors note this and do not fully reconcile it (Abd El-Wahab et al., 2021).

In the 56-dog trial, faecal scores held at 3.3 across every group on a different five-point scale, with no difference between insect diets and the control.

So: comparable to conventional protein meals, better than poultry meal on the scored measure, with one objective measure pointing the other way.

This is quite a common thing our customers contact us about, and it can be caused by a number of factors, including a change in dietary fibre.

A change of diet may change stool volume and consistency for a period while the gut adjusts, particularly where the two foods differ in fibre. Our advice would always be to transition diets gradually, and give it time before judging the food. If your dog’s stools become persistently loose, more frequent or progressively worse, you may need to contact your vet for advice.

Not in a way anyone has clinically shown to be beneficial.

You will find brands saying insect protein is anti-inflammatory or rebalances the microbiome. The one trial that examined faecal microbiota in dogs found that replacing 20% of dietary protein with defatted larvae meal shifted bacterial populations in ways its authors viewed with caution, and reduced protein and organic matter digestibility at that inclusion level. Their conclusion was that long-term feeding at 20% may have adverse effects (Jian et al., Frontiers in Microbiology, 2022).

The trial that measured immune markers directly found no effect at all (Kröger et al., 2020).

Black soldier fly larvae are genuinely rich in lauric acid, a medium-chain fatty acid with documented antimicrobial activity, and a 2021 review surveys that literature (Borrelli et al., Frontiers in Microbiology, 2021). But the evidence it reviews comes from pigs, poultry, rabbits and fish, not dogs — and lauric acid sits in the fat fraction, so a defatted larvae meal carries much less of it. We will say more when there is dog evidence to say it from.