I previously argued that, at least for a moderate vegan, the using of animals as objects rather than individuals of value characterizes almost all real-world agriculture. It is this attitude that leads to the deplorable conditions and treatment of animals in agriculture. If we treated animals as individuals of value it would be far harder for us to ignore the horrors of animal agriculture.
But isn’t this being naive about the realities of life for all animals including ourselves? It would seem to condemn the actions of subsistence farmers who are merely trying to provide calories to their families. Such farmers certainly use their farm animals as mere means, but it would be odd to fault them for this. Similarly the hunting or fishing of animals certainly uses them as a means for sustenance. When we hunt and fish we do not care about them as individuals. This gets to another critique by vegans about modern rich world agriculture: that it is unnecessary.
The moderate vegan can allow that there are some situations in which it is permissible for humans to use animals as objects - if it is necessary for survival - while also claiming that modern agriculture is never permissible because it is not necessary for human survival. This also brings clarity about why the vegan lifestyle makes particular sense in rich countries in modern times.
This solution is even more general than it may at first appear, because it also provides an explanation for why animal welfare should become more important to people as society becomes wealthier and the need for products from animals becomes less pressing. This also provides a ready explanation for why vegetarianism/veganism become more popular and animal welfare becomes more pressing in those societies - people are responding to the ethical reasons that they actually have.
When we decide whether to kill any living creature, we should decide whether it is necessary to maintain our own welbeing. However, even if this is true we still must determined the standard of welfare that we should apply. A vegan will likely want to apply some very high standard. Perhaps it is only permissible to kill any other creature in order to save our own lives from very likely death or major injury. A carnivore could opt for a very weak standard, such as any significant decline in welfare. This could include a decrease in welfare from not experiencing the pleasure of eating meat. We are left with another puzzle that we need to work through.