Depending on the size of the animal, pets are considered middle-aged to senior around 5-7 years. And as our pets age, their nutrient requirements change too. Senior diets, for example, are generally lower in calories but higher in fiber, and often have supplements specific to this lifestage such as joint support and antioxidants. AAFCO does not have requirements for senior pets, however, so look for a food labeled for “adult maintenance.” This is because an “all life stage” food is formulated with kittens and puppies in mind. It will also deliver too much fat and nutrients your senior pet does not require. In fact, the pet food could even be harmful to a senior pet.