For the particular case of antibiotic use, what I've seen is that farms with 10 cows generally apply antibiotics only when needed and farms with 500 cows generally apply antibiotics by putting it in everyones feed; it makes economic sense for both of them because of differences on how they work with these cows every day.

Large agribusiness do other deplorable stuff - i.e. letting cows die and collecting insurance instead of treating them, etc...

From what I've seen, letting cows die or mistreating them is a much worse problem in small agribusiness.

This of course depends on local regulation and legislation. But at least over here (northern EU), the bureaucracy is heavy and requirements quite strong.

Large-scale farming units have internal processes and they have more resources; there are many people doing the work with more thorough official oversight. Small-scale animal care, i.e. family or single-person farms, may be dependent on one person only. When illness - particularly mental illness - or old age kicks in, the animals may be neglected or mistreated in abhorrent ways.

On the other hand, small-scale agribusiness is also where the best animal care can be seen, there is actually an emotional bond between the carer and the animals.

Bad care is eventually caught because when you can't treat your animals well, you won't do your paperwork either. However, it is a strain on small farms as there is a fixed overhead in paperwork that is not much dependent on farm size, so there's a lot more to do per animal on small farms and thus there is more work/cost.

Any citation for this? If this was actually a widespread practice, I would think their insurance premiums would be prohibitively expensive!

Anecdotal observation. It is a public secret amongst farmers where I live.

I suppose it is possible that large agribusinesses where you live do this... it is also possible that the small farmers near you have an axe to grind with their larger competition, and/or are open to accepting and spreading gossip and rumors without much basis in reality.

But you don't think it's possible that all the incentives are geared towards this kind of behavior?

That is certainly a possibility! I didn't mean to imply it wasn't. I did a some quick looking and if your in the US, the USDA guarantees livestock insurance, this likely results in a distortion of the risk and perhaps shifts the incentives towards this sort of behavior.

But I would caution against taking rumor and gossip as strong supporting evidence.

Because all the incentives and subsidies are geared towards big agribusiness.

Small agribusinesses are hardly getting by.