Colibacillosis is a quiet tax on broiler production. It rarely shows up as a catastrophic die-off. It shows up as wet litter, birds that stop gaining, feed conversion drifting the wrong way, and a treatment bill that keeps coming back. For decades the response was automatic: reach for an antibiotic. That response is running out of runway. Antimicrobial resistance has turned the routine into a liability. Resistant Escherichia coli from poultry routinely shrugs off tetracycline, ampicillin, trimethoprim and gentamicin, and those strains do not stay politely inside the barn. They move through hatcheries, through the food chain, and into human medicine, where the options get narrower and more expensive. Regulators…