How does one determine that they are healthier after eating something they butchered themselves vs something butchered and bought at the store?
For one, the taste.
I will say, I've not be fortunate to have the opportunity to dress my own fowl' but, when I catch and cook my own fish/shellfish, the taste is way different than if I buy fish.
When I go to a farm and buy fresh buffalo meat and cook and compare that to the buffalo meat I buy at the store, again, same type of difference. I don't even know I'm eating the same animal.
Even fresh eggs react differently in the pan vs. store bought.
Something during processing? I don't know.