We should at least factor in how natural or pleasant their existence is. Or else a maliciously engineerd creature which spreads like crazy but is genetically bound to suffer immensely all their life is somehow preferrable over a local population of happy birds.

The species we use to harvest their products and body parts are often unable to survive naturally, some suffering from accumulated genetic defects, like being unable to support their artificially increased body weight.

If we don't need to reserve pastures for human-cows, there might be a chance for natural species to grow their numbers again.

Not really. We had a similar reduction in the global horse population at the beginning of the 1940s. We used to have basically a couple horses per person there for a few thousand years. We still have plenty of horses, most even have better lives now. Hopefully we can finally make horse racing financially unviable so we stop killing so many horses for no good reason.

There are already people who have pet cows that they won't eat when the cow dies. Those people will tend the smaller herds.

i dont care about the species, i care about individuals