Comparison of two 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 effectiveness of a new oxytetracycline formulation, administered either intramuscularly (BMI) or subcutaneously (BMS), to a currently available oxytetracycline formulation, administered intramuscularly (LAB), for the prevention of bovine respiratory disease (BRD) in feedlot calves. All experimental treatments were administered upon arrival at the feedlot and again on the third day after arrival.Over the entire feeding period, there were no significant differences (p>/=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 were no significant differences (p>/=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. However, during the first seven days of the feeding period the BRD treatment rate in the BMI group was 1.55 times (p<0.05) higher than in the LAB group. From days 1-90 and day 1 to the end of the feeding period, the overall mortality rates, BRD mortality rates, and BRD case fatality rates were two to six times lower in the BMS and BMI groups as compared to the LAB group; however, these differences were not statistically significant (p>/=0.05).These data indicate that both the intramuscular and subcutaneous administration of a new oxytetracycline formulation are comparable to the intramuscular administration of a currently available oxytetracycline formulation when given to calves upon arrival at the feedlot.