[jmartinpetersen]

It's been known since the 50's that giving penicillin to livestock increases growth rate. Farmers have understood that and used that.

The antibiotics counters and interacts in all sorts of ways we don't really understand (similar to how we don't really, really understand how the human gut works), but one of the ways it surely works is to counter problems caused by unsuitable living conditions.

Ending crop subsidies is probably a good idea in most of the world, but it certainly won't solve the overuse of antibiotics in agriculture.

[Qantourisc]

In a way this is surprising to me. Shouldn't this destroy the gut flora, making it harder to digest/use the food ? Then again their entire gut flora might be anti-biotic resistant ....

[maxerickson]

Several of the antibiotics in use as feed additives act selectively, changing the mix of microorganisms rather than destroying them all.

I swear I'm not a shill for big ionophore, but this is something they do in ruminants, they shift the mix away from one that tends to lead to "bloat" when the animals are fed a lot of grain.

[bodski]

Gut flora in humans appears to have a significant influence on weight gain/loss. Perhaps ABs fed to livestock tilt towards weight gain.

[IslaDeEncanta]

Actually, that's often the case with cattle.

[Fomite]

Cows can have pretty intensive levels of antibiotic resistant gut flora.