Maintenance energy requirement (MER)

The maintenance energy requirement (MER) is the daily amount of energy a moderately active adult animal needs to hold its body weight steady, neither gaining nor losing. It is the practical starting point for working out how much to feed, and it is usually derived from the resting energy requirement multiplied by an activity factor. MER is not a fixed number: it shifts with age, activity level, breed, environmental temperature and, importantly, neuter status. Neutering is one of the most underappreciated variables: a neutered adult dog or cat may need roughly a quarter less energy than an entire one of the same weight, which is why post-neutering weight gain is so common when portions are not adjusted (NRC, 2006). Cats, being smaller and often less active indoors, have a lower absolute MER than most dogs, and indoor lifestyle pushes it lower still. On a pack, manufacturers translate MER into feeding tables expressed in grams per day by body weight, but these are population averages: the right amount for an individual is the one that keeps a healthy [body condition score](/glossary/body-condition-score). MER works hand in hand with [energy density](/glossary/energy-density) and the food's [digestibility](/glossary/digestibility) to determine real portion size. Browse the [Petipedia glossary](/glossary) for more on feeding calculations.

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