Apples = cyanide poisoning?

My niece and I went apple picking over the weekend and brought home a huge bag of apples to share. Of course, Waldo was intensely curious about the bag too. On Monday, he managed to steal an apple and played with it/ate it over the course of an hour or so. I thought "oh, how cute!" when I noticed that he ate it from the bottom-up (core and all).

Well, not so cute as I have since learned that the seeds in apples are not good for dogs. The seeds contain cyanogenic glycosides that break down as cyanide when digested. Not good. I can't seem to find any information on the levels of toxicity, but I can only assume that he will be okay since he is still alive and kicking two days later. Now I feel foolish for thinking that it was cute and at least the apple would give him more fiber in his diet.