Thanks for all the replies everyone!
I was just wondering because my dog has started to go grey around the muzzle and he's not quite four years old yet. He's a black lab X collie and I'd expect him to make fifteen years no problem. So I thought he was going grey very soon. And that just got me wondering about what happens when hens get old...
Unless he's been in the powered doughnuts.
LOL! That wouldn't surprise me, he's a right little piggie.