I'm not an expert here but my assumption would be that every animal will slightly different requirements depending on age, gender, activity, conditions, and likely several other variables I can't think of.
Because of this it would be important to first determine what the current Kcal per kg is and adjust as needed. 5.6 Kcal/kg might be a good starting point if someone has no idea, but I think we can find a better starting point if enough of us can begin recording kcal/kg and monitoring.