Earlier quoted context omitted.
This is a false dichotomy. The choice is not lab grown or suffering. Farmed animals could live happy, healthy lives and then be culled in a humane way. The problem is that it costs slightly more and our society is more concerned with cost than animal suffering.
> Farmed animals could live happy, healthy lives and then be culled in a humane way. Breeding animals _specifically for killing them_, no matter how they are killed, is not what I'd consider humane. If we take 'humane' literally, it means to be treated as you would treat a human. I doubt we'd do this to humans. So the only way to be okay with this is adhering to a form of specieism.
If those animals would not be grown by humans, it could still be said that in their natural conditions they are grown specifically to be killed at some time, since few animals die "of natural causes", instead of being killed either by predators or by parasites.
For examples, my grandparents grew chicken. There is no doubt that those chicken had a more pleasant life than any wild chicken. During the day, they roamed through a vast space with abundant vegetation, insects and worms, where they fed exactly like any wild chicken would do. They also received from time to time some grain supplement that was greatly appreciated. They were not permanently harassed and stressed by predators, as it would have happened in their natural environment.
From time to time, some chicken was caught and killed out of sight. This would shorten the lives of the chicken that were not left for egg laying, but in comparison with the lives of wild chicken, most of these domestic chicken would have still lived longer on average.
So I think that as long as domestic animals do not live worse than their wild ancestors, this can be called as a "humane way", even when they are grown with the purpose of eventually being killed. At least being grown by humans has ensured the survival of the species of domesticated animals, while all species of not very small non-domesticated terrestrial animals have been reduced to negligible numbers of individuals in comparison with humans and domestic animals and for most of them extinction is very likely.
Unfortunately, today it has become unlikely to see animals grown in such conditions, like at my grandparents. Most are grown in industrial farms in conditions that cannot be called anything else but continuous torture, and I despise the people who torture animals in order to increase their revenues.