Do animals go grey in old age?

I believe all animals that have fur go grey with old age - for example monkeys do - we all know about cats and dogs doing it! Birds may change the colour of their feathers but I don't know if they actually go 'grey'. Some fish also change colour as they get older but again not necessarily 'grey'. Dolphins and other mammals don't really (unless they have whiskers, then they do! such as seals). I could be wrong, of course.....

My rough collie had more white hairs on his muzzle in his old age. My uncle has horses and if my perception is right, they do get white hairs in old age too.

Yes I do believe that every animal get gray hair when they grow old.

I grew up on a farm and, unfortunately, most animals were not able to remain there into old age. However, my Dad had two horses that he kept until they were into their mid twenties. In their old age, they had quite a bit of grey around their mouths with some scattered through their coats. And we had one milk cow that developed grey in the same areas. A friend of mine had a cat well into her 18th year who had grey around the mouth/nose with a very few in her coat. The most noticeable indicator of her age was her gauntness.