I know most people don't really bother looking at AAFCO recommendations when it comes to home-made recipes, but I did up an AAFCO recipe calculator to try and prove to my vet that my recipes are nutritionally complete. For the most part, it worked out fine. Playing around with it, I learned some interesting things about the formulations of commercial foods using veggies/grains/etc. and also found that horribly imbalanced foods can easily meet AAFCO standards since the majority of nutrients have no max values, nutrient ratios are generally ignored, and many nutrients that can easily reach toxic values are left out because they aren't deemed nutritionally essential.
Anyway, when it comes to home-made food I found that my own recipes and the most popular recipes online were generally AAFCO-compliant, with a couple notable exceptions.
Any thoughts on these? The minerals in particular got me a little worried. I haven't had time to check the AAFCO citations to see what the basis is for these particular values, but I plan to. Has anyone had issues with long-term use of recipes using eggshell powder as a calcium source?
Anyway, when it comes to home-made food I found that my own recipes and the most popular recipes online were generally AAFCO-compliant, with a couple notable exceptions.
- Methionine. Almost all meat-based recipes exceed AAFCO's upper limit of methionine, which is 1.5% on a dry matter basis or 3.75g per 1000kcal. This limit is based on studies associating neurological problems with high concentrations of methionine. Naturally, meat (including organ meats) contains a lot of methionine. I found that rice or peas can easily be used to balance that out, which would explain why many canned foods include such ingredients even though they don't require binding agents like kibble does. Using high-calorie meats such as lamb also balances this out, at least when using per-calorie measurements, but is still problematic on a dry-matter basis. That said, meats tend to contain a much higher ratio of methionine to cysteine than grains or vegetables would, so I would assume that much more of the methionine would be converted into cysteine in cats on a meat-based diet than would be seen in a diet with veggie/grain fillers. I haven't been able to quantify this difference, though, so I'm not sure.
- Minerals. This is not usually a problem with recipes using whole bone (including marrow), but makes things difficult when using eggshell calcium or calcium carbonate. I couldn't get complete numbers for MCHA, so I can't comment on that.
- Iron is hit and miss. Usually meat can account for all of the iron requirements, but poultry meats seem to struggle a little. It tends to be very close, though, so in a diet that rotates multiple proteins I wouldn't be concerned. Poultry-only recipes are fine if they include whole bone.
- Magnesium can easily be provided by eggshell powder, but not calcium carbonate.
- Copper, zinc, and manganese are consistent problems. Bone gelatin and/or organ meats cannot provide these minerals without throwing other things way off balance, and eggshells do not contain any significant amount. Some veggies can provide these (it appears some commercial foods may use veggies towards this purpose), but the quantities required would bring up other concerns that are not addressed by AAFCO. It looks like synthetic supplements or whole bone are the only good ways to provide these minerals, yet I haven't seen such supplements recommended in any recipes using bone substitutes.
- Vitamin D. Most recipes get plenty from egg yolks and/or fish oil, but I thought I should point it out for those dealing with food allergies. There is some vitamin D in muscle meat and whole bone, but not enough to meet the AAFCO requirements. It's hard to say how important this is, since cats can synthesize their own Vitamin D (albeit inefficiently), and AAFCO has repeatedly lowered their minimum requirements for it over the years. I didn't really look into alternative dietary sources of this vitamin, but it may be worthwhile. I personally wouldn't recommend a synthetic supplement, as it would be very easy to overdose. At the very least, we should make sure our cats have plenty of opportunity to bask in sunlight.
Any thoughts on these? The minerals in particular got me a little worried. I haven't had time to check the AAFCO citations to see what the basis is for these particular values, but I plan to. Has anyone had issues with long-term use of recipes using eggshell powder as a calcium source?