Washington State University researchers recently investigated antibiotic use in 358 calves housed in hutches on a commercial dairy. Calves were assigned to four groups: antibiotic in milk plus the farm’s treatment protocol; no antibiotic in milk and the farm’s treatment protocol; antibiotic in milk with a targeted treatment protocol; or no antibiotic in milk and the targeted treatment protocol. All calves received one gallon of pasteurized waste milk per day. For calves fed antibiotics, neomycin and tetracycline were added to milk the first two weeks of life. The farm’s protocol for scouring calves included two injections of penicillin, two sulfa tablets, and a spectinomycin injection. Prior to the study, 90 percent of calves were treated using this protocol.

The targeted treatment for scouring calves included a bismuth solution and electrolytes if calves were dehydrated. Only calves with a fever got antibiotics (sulfa tablets or ceftiofur). Calves with depressed attitude or poor appetite also received a painkiller (flunixin meglumine).

Calves treated by the farm’s protocol had 70 percent more days scouring than targeted treatment calves, and calves fed antibiotics experienced 31 percent more days of scouring than calves not fed antibiotics. Targeted-treatment calves tended to have better weight gain and grain consumption as well. The researchers concluded that on this farm, where passive immunity was good, excessive use of antibiotics increased scouring. They suggested normal gut bacteria were disrupted, which could have made them less able to compete with pathogens or may have allowed growth of potential pathogens that were present.

Based on this study, routine use of antibiotics for scouring calves that are alert, eating and show no other sign of disease does not appear to be beneficial and may even be harmful to calf health. In addition, eliminating antibiotics from milk and targeting treatments would have saved $10 per calf in the first month of life.