You'll have to look up agonizing, I bet going through a machine with the sounds of your companions dying all around you is a lot more agonizing than choosing an unhappy life and living with those consequences
I would agree, but I've seen cattle being offloaded into an abattoir. A few trucks in a parking lot, one unloading into a corral, with a bridge/ramp headed into the building.
I've seen startled cattle, and I've seen frightened cattle. None of these were. Yet inside, the sound of dying cattle could be heard, with a "Bam!" from the gun used to euthanize by nail-to-the-brain, and a "thud' of the cattle falling afterwards.
I presumed, at the time, that the lack of concern was due to a lack of panicked sounds. The cattle simply died instantly, without exhibiting any pain response, or noise, first.
So no.. at least for cattle, it seems to be without the experience you describe.
I bet if we had cow psychologists they might diagnose them with shock, living near pig farms my experience is a lot different. The stress of transportation, the smell of dead animals, these are so unnatural and without any possible escape what would you do?