My almost six-month-old male Cardi seems to have hit a major growth spurt this week, gaining nearly three pounds since last Tuesday (he's over 28 lbs.). My smaller male's breeder told me (when we got him) that males can have painful growth spurts and that I should switch from puppy to adult dog food between ages five and six months to help prevent this. Has anyone ever heard of this? My vet recommends leaving the pups on puppy food until they're a year old.