Morgan ate wellness core with no problems. Kibble size was fine and didn't have a problem with the transition. For your pup however the core might be too rich for him. You can try transitioning very very slowly. only adding a few core kibbles a day, and take about 2-3 weeks to do it.
when i tried to put morgan on Innova Evo she did the same thing as your pup. started throwing up. It was just too much for her.
__________________ Kellie  and  Morgan |