Pick ingredients from each group, choose how much of each, add the optional “boosters” that carry the things pellets miss, set how much to make, and get a recipe, shopping list, and rough cost, with a built-in safety check. On forms: grains go in dry (rats are granivores); pulses, beans, and starchy roots need cooking; fruit, veg, and greens can be fresh or freeze-dried; feed fermented foods unheated to keep the cultures alive. Honest caveat: targets are extrapolated from the laboratory (Norway) rat; weigh your rats and adjust. Prefer a quick reference? See the filterable food list.
Suggest a food worth adding to the builder, or flag a safety warning or feeding tip. A source link helps. Nothing appears until a person verifies it, so it will not show up right away.