Absolutely I can provide you some details!
The changes occurred in the summer/fall of 2008. I will provide some of the details on the Acana Small Breed Adult:
New formula had smaller kibble size and harder kibbles.
Old formula 28% protein, new formula 33%.
Old formula single protein source, new formula 3 sources.
Old formula didn't have salmon, new formula did.
New formula had lower omega 6 and omega 3.
New formula had proportionately much lower omega 3, omega 3 sources are expensive.
All this happened overnight, new stock came in with different bags, different ingredients, different guaranteed analysis, same name, but built for different dogs and unfair for any unsuspecting owner who assumed a new bag of the "same" food wouldn't be a sudden drastic diet change.