My girl ran after the huntng big ones at age 7 mths , of course not so long ; this is the age all 5 started running off for a bit longer with te adults , really long ( 10-15 minutes ) then with 10-12mths , they determined this themselves as they are off leash from the get go here and thus can build up good bones/ligaments and condition in teir own pace . Perhaps you can give her a run - she has to get the agility , too , and then take her back on leash initially .
And , why would you want to muzzle her ? I have never found it necessary with any of my dogs or hounds and find , that muzzled dogs look quite frightening ,the poor sods - this is at least , what I think , " the public " will perceive.