Old age arrives on a sliding scale, and feeding for it is less about a special bag than about noticing what has shifted in a particular animal. A few things reliably do.
When 'senior' starts depends on size
Age catches up with a big body faster. A giant-breed dog may be a senior at six or seven while a small terrier is barely middle-aged, and cats generally cross into their senior years around eleven. That size effect is the same one that shortens the lives of the largest breeds — visible on the breeds page, where the giants carry the shortest recorded spans.
What the body needs differently
Metabolism slows, so the same bowl that kept an adult trim can quietly add weight to a senior. Appetite and sense of smell often fade, making palatability matter more. And the old instruction to cut protein for aging pets has largely reversed: unless a vet is managing a specific condition, older animals generally need as much good-quality protein as before, or more, to hold on to muscle.
What to actually adjust
More than the food, it is the oversight that changes: regular weight checks, more frequent vet visits, and attention to teeth, since dental pain is a common and overlooked reason an old pet goes off its meals. Senior diets vary from genuinely useful to mostly marketing, so the safest guide to whether one earns its place is the vet who knows the animal's kidneys, joints and weight.
At what age is a dog or cat a senior?
It depends on size. Giant-breed dogs can be seniors by six or seven, small dogs not until ten or later, and cats generally around eleven. Larger animals age faster, which is why there is no single number.
Should I feed an older pet less protein?
Usually not. The old advice to cut protein has largely reversed — unless a vet is treating a specific condition, older dogs and cats generally need as much quality protein as before to keep muscle. Ask your vet before restricting it.
Why has my senior pet stopped eating well?
Fading smell and appetite play a part, but dental pain is a common and easily missed cause, and so is illness. A senior that goes off its food is worth a vet visit rather than only a change of menu.