I have had young deer tougher then old deer, had relaxed deer tougher then none relaxed deer, does tougher then bucks, farmland deer tougher then forest deer,etc. Other then a poorshot ie: gut shotI think it is more the hand your dealt when it comes to venison in many cases. Saturday I shot a mature mulie dry doe, she was chalked full of fat and was already starting to stink. Honestly i figured she'd beheaded straight for the grinderbut in deboning it tonight I found it hard to cut as she was so tender. My partners was a younger doe and she was nothing like mine. Both deer were relaxed, standing, never travelled a step after the shot, same food sources and care after the shot. Sometimes you are the butt, while others your the boot. Though i certainly believe a clean harvest is always the best and as such the vitals IMHO are the best shot placement to ensure this.
An importantfactor is the care after the shot quick cooling of the carcass(FD, skinned & hanging asap), relax period of 24hrs (if temp allows), debone, remove fat, silverskin, hair,etc. When it comes to cooking rare is best and no more then med rare. Remember meat continues to cook after it is pulled off so factor this in your meal plans

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Enjoy and best of luck this season.