
Hi Gem
I wouldn't be in too much of a hurry to change from the existing diet unless it was one which I really disapproved of (in which case I'd have been unlikely to be getting a pup raised that way ;) )
The change in store for a new puppy, i.e. lack of mum & siblings company, travelling from breeders, arriving at strange and (to baby puppy) scary surroundings with new people etc can all affect a tiny tum. Not least, if you stay outwith the breeder's local area, your water may well upset the pup's tummy initially too :) Add to that everything else the puppy has to experience which will be so different from it's place of birth and there's usually a lot of stress in store so I believe we have to minimise the stresses where and when we can (diet being one of the few we can control :) )
I'd personally wait a minimum of 2 but pref 4 weeks after bring your new pup home before implementing major diet changes and then phase same in over a further 10-14 days :)
HTH, Teri