The rule of thumb is that you should be able to see the outline of the last 3 ribs, the tips of the hip bones, and a bit of the spine. Usually the ideal pet weight is about 3‑5 pounds heavier than the racing weight. When the greyhound is viewed sideways, there should be a nice curve (“tuck up”) between the end of the ribs and the thighs. Allowing your greyhound to become heavier puts undue strain on the heart and on tendons, ligaments, and joints, which can lead to more problems with arthritis.
However, unless your greyhound has a tendency to gain weight, older greyhounds do not need to be put on a senior diet. In most cases, the trick is keeping weight on the old dogs, not taking it off! Low protein diets can also lead to muscle loss and wasting.