Hi M & C
I’ve gone down many a rabbit hole over the years. Hunting down accurate information can be a frustrating endeavor. Here is my take on NRC. NRC numbers are based on high bioavailability, something that in the real word doesn’t necessarily occur. AAFCO takes the info from NRC and pads the numbers to account for bioavailability.
AAFCO tables are by kg DM, assuming 4000 kcals/kg and they also report nutrients/ 1000 kcals . NRC does this too, but NRC also provides amounts based on body size. For example, NRC rec 3.28 grams of protein/ kg bw to the .75 power.
AAFCO tables are in Mins and Maxs. NRC has 4 columns: min, adequate, rec and safe upper limit. For many nutrients a SUL is not given because there is not sufficient research as to where to draw that line. For adult dogs there is no reported SUL for CA or Phos. For growth the SUL is 1.8% with a 4000/kcal/kg DM diet. This was based upon large breed puppy growth.
Currently I believe AAFCO table for MAX Calcium is 2.5 % EXCEPT in the case of growth of large breed puppies in which case it is 1.8%. This is why an AAFCO statement may say formulated to meet all life stages except growth of large breed puppies.
The point I was trying to make, and didn’t explain well, is that when AAFCO sets its tables it assumes that the dog is eating an average amount of calories but doesn’t define what this amount is. They leave it up to the manufacturer to determine feeding recommendations. This is a huge weak link.
It is known that when calories are calculated, any individual dog can vary by 50% from this number. So, for example, if calculated calories are 500, one individual may need 250 and another 1000.
When diets just meet AAFCO min there is an underlying assumption that the dog will be eating 500 kcals. But for those dogs that only need 250 kcals that AAFCO min may not meet the dog’s nutrient needs on a weight basis as given by NRC.
I think FEDIAF addresses this by having two data sets with one being for “inactive ” pets, but I haven’t checked to verify this. I believe this is what Susan Thixton is trying to petition the FDA to address.
That may be the easier way to address this because actually determining caloric needs is fraught with a lot of variation. But I see it as imperfect as well because it still leaves it up to the manufacturer and I’ve found considerable errors with this approach. I’ve found multiple instances in which when using the nutritional information provided by the manufacturer and using the manufacturer’s feeding recommendations the dog would not consume enough nutrients to meet NRC rec. or sometimes even min. values.
I have only found this in high cost, small company products. IMO feeding amounts are set low to make the food look more affordable. IMO, one of the most egregious examples I’ve come across was in a freeze-dried product made by a company that apparently did have by a PhD in animal nutrition on staff. So apparently even having someone with an appropriate background in nutrition in the company doesn’t insulate the consumer from errors of this type.
On the other end of the spectrum, I’ve seen companies who boost all nutrients to well above AAFCO min to better cover these “easy keepers” AND have feeding recommendations that will meet the animal’s nutrient need.
I’ve seen as a rule of thumb that if your dog needs to eat 80% or less of the recommended amount you need to switch foods to something with a higher nutrient density. The problem is that assumes the original feeding recommendations are accurate and unfortunately, they in many cases, are not.
