Apples are great for dogs.. apple seeds are not.. experienced that first hand.
One night making home made apple sauce (10lbs of apples) and used one of these for straining the apples through it while trapping the skin and seeds.
Dumped all the junk into the trash can and some how my dog got into the trash and ate all the skin and seeds from the 10lbs of apples. Quick call to the vet required a 35 minute drive at 10:30pm to an open pharmacy to get hydrogen peroxide. Two capfuls of that and within 2 minutes he threw it all up outside.. what a MESS!!!
All was ok after that thank god!!
And then there was the porcupine and the 110+ quills... but that's a different story all together..