Found this which gives some interesting information http://www.mypetsdoctor.com/hills-prescription-diets-alphabet-soup. The d stands for diet, the k for example in k/d would be kidney diet, h/d heart diet. From what I found c/d had been cat diet until Hills formulated a canine version of the food also. Rather interesting, and I do believe I may have too much time on my hands. I will get back to you about what type of cookies I would like to recieve
Well, they had to come up with some gimmick to make their food seem more prescription-y :tongue2:. But, yeah, they used to stand for something but now they just use whatever letter isn't used yet.