In just about every way possible that death is a world apart from what we do to most animals we eat. What we have deemed "humane" slaughter is really nothing else than an attempt to make the word humane devoid of all meaning. I stopped eating meat after seeing how a cow and some pigs from the local organic farm (held as a poster child by the meat industry in my country) were slaughtered.
They were afraid from the first second. The pigs lost consciousness while grasping for air in panic in a co2 gas chamber.
It was awful and nothing short of a disgrace.
New laws and policies promoted by the meat industry has now made inquisitions like mine impossible. All of this happens behind closed doors. I will never trust the industry to fix this. They will have to be dragged kicking and screaming into treating animals with respect.
They could have used argon, helium, maybe even nitrogen. Anything else that can lower oxygen concentration without the body noticing bacause it doesn't detect low oxygen levels, just high CO2 levels when you suffocate.
The jury is still out which gas is the best. I hope it'll be resolved before it's my time to go.
In all my experience with dogs (and animals in general), one of the many lessons they have taught me is forgiveness. Both of others and myself.
Note the "you could" part.
You did the best you could, and you obviously learned from your mistakes. Don't be hard on yourself, that's everyone else's job and they don't need the help.
I felt this way with the first dog I raised outside of my parents house. Things were slow but fast. One day I found a boil on her neck, rushed her to the hospital only to walk out with no answers a mountain of bills. I spent months seeking more answers with new testing. She was still the same old dog, playing with my other dog constantly. She'd do silly things, demand walks and pets, and stomp/parade around the house with her toys. I begged every night that she make it to her tenth birthday. She did, then shortly after her birthday she'd struggle to eat for days at a time and was acting sleepy. On the third day I brought her to the vet and did the deed.
It still hurts remembering her sleepily lay in my lap one last time and watching the life quietly slip away. That was the life I nurtured and the life that guided me to be more of a man every day. A life that demanded evolution and growth out of me in the most compassionate way possible. The vet felt her stomach and said, "Her liver is covered in tumors. You did the right thing." Then I began to reflect; had I been selfish? When I found the boil, was that when I should've done it? What about after all the testing? What about when she'd protest her food for a day? Two? Inevitably, I decided somehow the magical number was three.
The only thing that gives me solace is that I consulted the vet constantly on when was the right time. She'd never directly answered me; that choice was mine, a choice I absolutely feared. The advice that sticks out was, "When the dog you know stops being the dog you know." I know in my life I'll have to do this again and I don't think it'll ever get any easier. There's no right answers to this intersection of life, only wrong and less wrong ones. Love is a very tricky thing, especially with a friend that can't say much.