Majority of emphasis is put onto how a Breeder raises a litter and the nutrition that is supplied to mom and kits, yet we forget that kits go to their new homes anything from 6 weeks to 8 weeks of age.... What does this then mean for the new owner?

The Rapid Growth Phase is up until 10 weeks of age, meaning that extra protein shall be required to be fed by you until your new little critter is 10 weeks of age. This may result in your current colony putting on a little extra weight during this time period, but do not stress, as once the new critter is put onto adult rations the others will loose the weight they had gained. 

Things to include during this time period is egg - Boiled, scrambled or mixed into rice (brown) and then microwaved or a chicken carcass or perhaps drumsticks, include some Kale during this time period as well, and any other veg that you may have in the house. 

Do remember that you are not trying to fatten the rat at all, but merely provide nutrition to ensure that muscles and bones develop appropriately, so avoid adding more treats to your mix or feeding high fat meals.