Reduced antibiotic use in livestock: how Denmark tackled resistance

"Low-dose, prolonged courses of antibiotics among food animals create ideal selective pressures for the propagation of resistant strains,"[6] wrote Stuart Levy, a medical doctor and microbiologist at Tufts University, who tracked the phenomenon in a 1974 experiment on a small farm. Schlundt says mass administration of low-dose antibiotics continues for the stated purpose of disease prevention, despite a lack of solid evidence that dosing whole herds this way is a reliable prophylactic.