I would say the same 3.5 +. Without getting my finger in its mouth and taking a look at the molars, cusps, dentine\enamel lines and also the skull thickness. I came to this conclusion because of the neck size (don't think he's rutted up as I still see allot of green foliage in the background) the swayed back, bigger belly and the muzzle diameter. But when all else fails giving him a reach around and checking the size of his cajones is a sure bet to the age! The bigger they are the older they are

Thats my story and I am sticking to it!