Let's say I were to describe a living thing, that despite having no nerves or brain we could identify, responded to favorable stimuli in ways we could easily describe as a "favorable response" -- for example, the presence of usable energy would provoke the movement of appendages towards that energy source, and the presence of unfavorable or damaging stimuli would provoke an "unfavorable response", such as pulling appendages away from negative stimuli. As far as we could tell, the intelligence in this thing was perhaps entirely distributed throughout the creature rather than relying on a centralized processing center metaphor for thought. It doesn't seem to think in any way that we can easily translate, and for a very long time, we didn't even recognize they responded to stimuli at all -- but that's our fault.
This creature also can't make head or tails of us we presume, our experiences of the universe are simply too entirely different. We have a few appendages, bilateral symmetry, and a mix of sensory organs -- mostly in the same appendage stalk as our central thought organ. Perhaps instead of our familiar mix of sense, this creature had an entirely different set that prioritized entirely different things -- perhaps instead of taste, the organism had some alternate way of assessing chemical composition, instead of sight, it had thousands of narrow-band EM sensing organs on the end of each appendage. Perhaps its digestive system was on the outside, a little like ours, but also turned inside out, so it merely had to have external contact with usable nutrients, not ingest it. Perhaps it transported nutrients around without a central cardiopulmonary organ but using nothing but capillary action, lungs were distributed on the underside of each of the EM sensing organ and it's "blood" didn't rely on metals to bind to Oxygen but instead was simply a nutrient stew. What if the bulk of its carbon (sure, its carbon-based) came not from food, but was simply pulled out of the air?
Let's suppose this being had no mouth or way of making noise, but communicated with its fellow species using various chemical exchanges, for example, suppose one of the creatures was attacked, it might release warning chemicals into its environment letting others of its species prepare themselves by pulling back appendages, or reducing the flow of its internal blood analogue. Or perhaps when mature members of the species learned of new sources of nutrients, they might share those nutrients with young members of the species through this exchange network. Perhaps the way this species "screams" is by releasing a gas into the air that warns others nearby.
Mating and reproduction depends on the species, but there are sexes. Species members have various life-stages that include an infancy analogue, a childhood analogue (with growth spurts), a sexual maturity stage and many even have old age. Some species can reproduce on their own, others require symbiotic species to help facilitate reproduction.
If creatures like this dropped out of space in a spacecraft we'd call them aliens and see if we could learn their language and their technology.
Would you think of this creature as something that can suffer?
All I've described are plants.
> How much energy/resources/time does it take to raise plant food sources vs an analogous amount of animal food sources?
Animals require more energy to raise than plants in general. However, animals can be raised on food stock that both:
a) humans can't eat
b) grows where human ready food plants don't grow well
> Do plants require antibiotics to raise at scale?
Yes, as well as other various chemicals and treatments from chemicals that kill non-desirable plants to chemicals that kill non-plant animals, to chemicals that kill fungi or bacterial infections. Plants even get viruses.
> What are the environmental tolls taken by raising plants vs animals?
Very difficult to ascertain. The world will have animals in it one way or the other. But nearly all domestically raised plants and animals are the product of thousands of years of engineering and intense cultivation. For example, cabbage, broccoli, cauliflower, kale, brussel sprouts, collard greens, savoy, kohlrabi and gai lan are all human engineered variations of the same plant. This plant only occurs naturally in very specific ecological niches. One could argue that the millions of acres dedicated to growing these mutants are millions of acres where the natural ecology is permanently damaged. But humans have been at the cabbage game for a few thousand years, it would be impossible to know what nature would have intended for that land.
Similarly, cows are famously highly domesticated food, clothing, labor and milk animals with few close wild cousins due to about 11,000 years of intense selective breeding. But there's something like 1.5 billion cows in the world. If we stopped eating cows today, there'd still be 1.5 billion cows. It's obviously not ethical to just kill them all. Is it ethical to deny them natural breeding rights as well? Cows appear to take pleasure in their offspring, would it not be a slow genocide to simply end their line? We can't ask cows, they don't talk, just as much as plants don't, but we know they have emotions and moods, can be happy, excited, fearful or sad. Would a cow feel sad if it knew it could never have calves?
So until we can give a precise, reductionist definition of what suffering is - and enumerate all that can/can't experience it - then animal treatment is not an ethical question? Given a hammer and a choice to hit either a kitten or a rock for $10, what distinctions between the two would you make to help your decision? I think a central nervous system and/or an analogue for a response that we recognize as pain are a decent starting point.
What proportion of meat-based meals are eaten instead of plant-based meals specifically because of that lack of human ready plant food being available?
Do the bacteria which are targeted by plant antibiotics pose a similar risk to humans as the bacteria that affect livestock such as pigs?
It might be ethical to euthanize a majority of cows etc., if it could be done instantaneously, painlessly, and somehow without creating humanitarian or environmental issues. It would have to be a perfect hot swap, though.
When technology and space exploration allows, I would also support simply relocating these Earth species en masse to other customized planets where they can live/suffer/die in more natural or "fair" terms without our systematic interference.
How much energy/resources/time does it take to raise plant food sources vs an analogous amount of animal food sources?
Do plants require antibiotics to raise at scale?
What are the environmental tolls taken by raising plants vs animals?