Stick a label on all CIA packages with red writing saying 'Critically important antimicrobial. Do you really need to use this?'
Start asking owners if they have had the horse weighed recently or have a weigh tape, it's surprising how many do, and then you can get your dose accurate.
Use culture and sensitivity testing routinely, trust the results and trust the antibiotics. Use first line, licensed antimicrobials unless a lack of sensitivity dictates otherwise.