Subtherapeutic tetracycline effects on recovery patterns of calves after Salmonella typhimurium challenge.
Holstein calves were maintained on a subtherapeutic dose of chlortetracycline to determine if an oxytetracycline therapy, given after a Salmonella typhimurium challenge, would be compromised by the previous subtherapy. Two of the four groups of seven calves were maintained on a subtherapeutic amount of chlortetracycline. All calves then were challenged with Salmonella typhimurium, and with the onset of clinical symptoms one group with and one group without subtherapy were given a therapeutic dose of oxytetracycline. The two groups receiving a therapeutic dosage of oxytetracycline had the most quickly declining body temperatures and the highest average body weights post-challenge. Two calves died in the group receiving no antibiotic treatments, and one calf died in the group receiving only the subtherapeutic treatment. There were no differences in postchallenge body temperatures or body weight changes between subtherapeutic and nonsubtherapeutic groups of calves. The conclusion was that the subtherapeutic dosing of chlortetracycline did not affect the therapeutic treatment effects of oxytetracycline after a Salmonella typhimurium challenge.