What you can change in the bowl, and what puts it outside the calculation
Not to the gram. Yes, within the food groups. The chart is not a recipe to reproduce exactly — it is a composition the correction was calculated against. Substitute within it freely. Step outside it and the sachet is correcting a diet you are not feeding, at which point the number we gave you is wrong, and we would rather you knew that than trusted it.
1 · What substitution is already covered
The system carries more tolerance than most people expect. Energy is served at a 10% buffer over calculated requirement, and cut-to-cut variation in meat is ±25–30% on its own — chicken breast against skin-on thigh, lean leg against shoulder, before any fat trim. Against that, the difference between your Tuesday and your Thursday is noise.
Swap between the permitted proteins as you like — chicken, mutton, fish, egg — in whatever proportions suit your week, your butcher and your animal. Vary the vegetables within the allowance. Use whichever cuts are good that day.
This is a statement about our evidence, not a concession. The validation ran across the permitted input space rather than one example recipe, which is precisely why substitution inside the groups is covered and a single-recipe claim would not be.
2 · The four exclusions, and the reason for each
These are exclusions rather than preferences.
Liver and organ meat. The largest of the four. Liver is extraordinarily dense in vitamin A and copper, both of which have real upper limits, and our sachet already carries a vitamin A load from a liver-derived palatant. Adding organ meat on top is how an owner overshoots. It is also why the specified bowl excludes organ rather than treating it as a bonus.
Bone. Calcium is the largest single correction the sachet makes, because muscle meat is calcium-poor and phosphorus-heavy. Add bone and the calcium is dosed twice. Separately, fed bone carries a genuine physical risk: gastrointestinal perforation is not a rare presentation in clinics.
Other supplements. A multivitamin, a joint powder, a calcium tablet, a fish-oil capsule on top of the sachet — each individually sensible, stacked they can push past the ceilings on the nutrients that have them. See supplements alongside Growlrr.
Carbohydrate load. Cats need at least 95% of calories from animal sources, dogs at least 85% counting dairy. Rice and starch displace the protein the animal actually needs, and for a cat in particular they are dilution rather than nutrition. A little during transition is fine; as a daily bulk filler it moves the bowl outside what was calculated.
3 · Verify it rather than take our word
We publish the tools instead of asking for trust. The free bowl checker takes what you actually feed and shows where it sits — it will tell you what your current bowl is short on before you change anything, and it works whether or not you buy from us. The 1 Million Bowl Test is the study behind the chart: over a million simulated bowls across the full range the protocol permits, each evaluated against NRC 2006 requirements and the applicable safe upper limits.
That study is why we can say substitution within the groups is covered. We did not check one example recipe; we checked the space.
4 · The boundary
You are free to feed your animal however you judge best. That is not our call to make.
What we will not do is sell you a correction for a bowl it does not correct. If your diet sits outside the permitted space, our sachet does not apply to it — not because we are precious about the chart, but because the dose would be wrong and you would have no way of knowing by how much.
Use the checker, feed what works, and if the two part company, feed what works.