I've been doing a home-cooked diet according to NRC calculations for 3 years now and have done a fair amount of reading and discussing on lists about the numbers and issues around them.
On lists which are run by nutrition experts (like K9Kitchen and TPC), the consensus is always that for a healthy dog you can easily go to 2x (or even higher) the NRC recommended amount of protein - this seems to be the preferred way (and what dog would disagree!), as long as everything is balanced out properly. [Note: this obviously applies to a home-prepared diet, not commercial foods.]
So IMHO the NRC so-called "optimal nutritional requirement" is a tad on the low side if you're keen to achieve glowing good health and your dog does not have any health issues that require a restriction of proteins.
Another factor to consider is quality and bio-availability of protein. However good the kibble ... surely nothing beats fresh meat.
I would also say that protein is in excess only if the dog's system cannot utilize all of it or struggles with breaking down that amount of it. Another example: my dogs cannot break down read meat efficiently and safely in larger amounts - therefore anything beyond a teaspoon of red meat is 'in excess'. They do not struggle, however, with utilizing white meat or fish - oh no, it fuels them very nicely. :) I also know that if I gave them only the NRC-rec. amount (9g of protein per day for a 4kg dog) they would struggle and their metabolisms would not be running at optimum.
If I was feeding mainly a dry food diet, I would always 'enhance' it with fresh foods - mainly meat/fish/egg plus some vegies and fruit.
Britta and the fussy toy poodles
