each and every single dog is difrent mate, start the dog at graft when the dog is physicaly and mentaly mature enough. cant put a time/age on it pal, some mature alot sooner and later then others, ie. ive a bitch here witch i statred at 9 months old, young some might say but this bitch was very mature for her age and she has proved maannny a times shes more then capable. she only had a few slips every outing up untill about 13 months then i upped the pace. but then like i've expirienced with pals dogs past and present some of them are'nt feild worthy untill somet times around the 18mnth mark,