An evaluation of the relative efficacy of a new formulation of oxytetracycline for the treatment of undifferentiated fever in feedlot calves in western Canada.

A field trial was performed under commercial feedlot conditions in western Canada to compare the efficacy of a new formulation of long-acting oxytetracycline (LA 30) to a standard long-acting oxytetracycline formulation (LA 20) and florfenicol (FLOR) for the treatment of undifferentiated fever (UF) in calves that received metaphylactic tilmicosin upon arrival at the feed-lot. Seven hundred and ninety-seven recently weaned, auction market derived, crossbred, beef calves suffering from UF were allocated to 1 of 3 experimental groups as follows: LA 30, which received intramuscular long-acting oxytetracycline (300 mg/mL formulation) at the rate of 30 mg/kg body weight (BW) at the time of allocation; LA 20, which received intramuscular long-acting oxytetracycline (200 mg/mL formulation) at the rate of 20 mg/kg BW at the time of allocation; or FLOR, which received intramuscular florfenicol administered at the rate of 20 mg/kg BW at the time of allocation and again 48 hours later. Two hundred and sixty-six animals were allocated to the LA 30 group, 265 animals were allocated to the LA 20 group, and 266 animals were allocated to the FLOR group.

A comparison of prophylactic efficacy of tilmicosin and a new formulation of oxytetracycline in feedlot calves.

Two replicated-pen field studies were performed under commercial feedlot conditions in western Canada to compare the administration of long-acting oxytetracycline at 30 mg/kg body weight (BW) versus tilmicosin at 10 mg/kg BW to feedlot calves upon arrival at the feedlot. Ten thousand nine hundred and eighty-nine, recently weaned, auction market derived, crossbred beef steer and bull calves were randomly allocated upon arrival at the feedlot to one of 2 experimental groups as follows: oxytetracycline, which received intramuscular long-acting oxytetracycline (300 mg/mL formulation) at a rate of 30 mg/kg BW; or tilmicosin, which received subcutaneous tilmicosin (300 mg/mL formulation) at a rate of 10 mg/kg BW. There were 20 pens in each experimental group.