Providing safe, efficient nutrients is not unnecessary suffering. I believe it is necessary. And animals can be slaughtered in humane ways with minima suffering (eg, halal, kosher, and other methods).

Animals can process inarable land and turn it into nutrients. I can have a cow graze on land that can’t grow edible food for humans and turn it into edible food. That’s efficient.

When you can get all the safe and efficient nutrients from living things that do not suffer, then any suffering is unnecessary.