Breeders and anyone else re-homing a puppy will tell you what he/she has been fed on - this is not cast in stone however, and you can change over to your own preferred diet, but DO IT GRADUALLY ....
Puppies are like babies of most other species in that their stomachs cannot tolerate anything too strong or fibrous or ungentle in any other aspect ...
Given that they can no longer have their mother's milk, we need to wean them onto their most natural diet carefully, and I suppose that the fact that most canine type mothers will, after breast-feeding their young, start them onto 'proper' food by regurgitating what they have previously eaten and letting their pups take it from their mouth, is a guideline.
This is why a very good way of bonding with an orphaned or young pup is to chew something (like toast crust or maybe even pizza crust) and then spit it out and let the puppy eat it ...(it has to be straight from mouth to mouth!) they then look upon you as their provider and it is basically up to you to give them what they need !! (Actually, I pretended when it came to the tin of savoury cuts in gravy ...!!)
As with human babies, things like boiled rice (making sure it is very soft and always fresh!*) or scrambled egg with diced toast or something else to provide extra roughage in the morning is great - I have always found that they enjoy this different meal from us trying to force down doggy bisc and meat or just doggy bisc !!
The boiled rice is a good sub for the biscuit if they are being picky - as for the amount of chicken, you need to cut it up very small (tiny cubes) and just put a desert-spoonful in and mix it well - if the rice has been chickenfied enough they will eat it all up !!
* Boiled rice apparently has a humungous pick-up of salmonella, so you either need to chill it immediately and then re-heat especially carefully, or just cook and serve .... don't let it sit around for a day or so otherwise all your efforts will be for nothing !!!!
