Thank you for your reply, Sue!
I think you are totally onto something. I just realized while reading your reply that a factor that might have contributed could be that I use Ziwipeak Lamb as training treats. They, too, are very rich. I did cut down on his regular food intake to level it with the Ziwipeak, but I guess in the end having two rich foods together could have been too much. For the last three days I used a different training treat for variety and while still mushy, his stools seem to have a little more form.
So I think I will end up making the switch to Acana and use lighter training treats.
