Thanks for your question!
I didn’t go as far as doing a cost-effectiveness analysis on this; I think that there are a lot of uncertainties that would make that quite difficult, but it’d definitely be a good next step for this topic.
My guess is that if we purely consider impact on animals then it might come out quite a bit less cost-effective than other interventions, but that if we account for public health benefits as well it might turn out to be comparable in terms of cost-effectiveness.
I think the two most important variables that cost-effectiveness would be sensitive to are whether/what kind of welfare adaptations farmers would make, and how effective antibiotic substitutes are. If we’re including impacts on humans then it would also be very sensitive to what proportion of the antibiotic resistance burden comes from antibiotic use on farmed animals!