COMPARISON OF 2 FORMULATIONS OF OXYTETRACYCLINE GIVEN PROPHYLACTICALLY TO REDUCE THE INCIDENCE OF BOVINE RESPIRATORY-DISEASE IN FEEDLOT CALVES

A trial involving 1,803 feedlot calves was conducted under commercial feedlot conditions in western Canada to compare the relative effective ness of a new oxytetracycline formulation, administered either intramu scularly (BMI) or subcutaneously (BMS), to a currently available oxyte tracycline formulation, administered intramuscularly (LAB), for the pr evention of bovine respiratory disease (BRD) in feedlot calves. All ex perimental treatments were administered upon arrival at the feedlot an d again on the third day after arrival. Over the entire feeding period , there were no significant differences (p greater-than-or-equal-to 0. 05) in the BRD treatment rates or the BRD relapse rates between either the BMI or BMS groups compared to the LAB group. Similarly, there wer e no significant differences (p greater-than-or-equal-top 0.05) in the BRD treatment rates in the BMI or BMS groups from days 8-14, days 15- 90, or days 1-90 of the feeding period compared to the LAB group. Howe ver, during the first seven days of the feeding period the BRD treatme nt rate in the BMI group was 1.55 times (p<0.05) higher than in the LA B group. From days 1-90 and day 1 to the end of the feeding period, th e overall mortality rates, BRD mortality rates, and BRD case fatality rates were two to six times lower in the BMS and BMI groups as compare d to the LAB group; however, these differences were not statistically significant (p greater-than-or-equal-to 0.05). These data indicate tha t both the intramuscular and subcutaneous administration of a new oxyt etracycline formulation are comparable to the intramuscular administra tion of a currently available oxytetracycline formulation when given t o calves upon arrival at the feedlot.