Energy requirements are quite variable among dogs. Animals with the same body weight can have 3-fold variation in daily kcal requirements, which are affected by age, neutering status, physiologic status (growth, gestation, lactation, etc), physical activity, environmental temperature, and any underlying abnormalities. Any recommendations for kcal requirements are only starting points and may need to be modified based on the response of the individual dog or cat.
Many formulas are available to calculate caloric requirements for dogs. A simple method for healthy dogs starts with calculating the resting energy requirement (RER). The RER is the energy requirement for a healthy but fed animal, at rest in a thermoneutral environment. It includes energy expended for recovery from physical activity and feeding. There is an exponential and a linear formula for calculating RER. The exponential formula (RER = 70 [body wt in kg0.75]) can be used for animals of any body weight, whereas the linear formula (RER = 30 × [body wt in kg] + 70) is restricted for use in animals that weigh >2 kg and <45 kg.
The maintenance energy requirement (MER) is the energy requirement of a moderately active animal in a thermoneutral environment. It includes energy needed to obtain, digest, and absorb food in amounts to maintain body weight, as well as energy for spontaneous activity. The formulas to calculate MER take into account age and neuter status.
Source: https://www.merckvetmanual.com/management-and-nutrition/nutrition-small-animals/nutritional-requirements-and-related-diseases-of-small-animals
