kongs

HI :D:D I now have my beautiful puppy- picked him up on Tuesday. He is 8 weeks old. Just wondered when can I start using chews- such as tripe sticks or pigs ears? And when can I stuff the kong with peanut butter. I am worried about upsetting his tummy but would like some treats to give him...

I have seen a lot of people recommending kongs stuffed with things to keep puppies entertained. Would these be suitable even for a 9/10 week old puppy who is definitely on the small side? Could anyone recommend a good one and some tasty fillings? Thanks :)