A Comparison of 3-, 5-, 7- and 10-day Post-metaphylaxis Evaluation Periods on Health and Performance Following On-arrival Treatment with Tilmicosin in Feeder Cattle

A Summary of Two Studies

Abstract

Two 60-day studies were conducted comparing various post-metaphylaxis evaluation periods (PMEPs) following administration of tilmicosin to beef feeder cattle at arrival-processing. Calves in Study I were randomly assigned to a control group (no metaphylaxis) or administered tilmicosin at label dose (4.55 mg/lb; 10 mg/kg BW) and assigned to a 3-, 5- or 7-day PMEP (n=160 calves per treatment). Morbidity due to bovine respiratory disease (BRD) was reduced (P <0.01) in calves treated metaphylactically with tilmicosin compared to controls (9.6 vs 33.8%, respectively). Average daily gain (ADG) was improved ( P <0.05) in all three PMEP groups compared to gain of calves in the control group. Calves in Study II were randomly assigned to a control group (no metaphylaxis) or administered tilmicosin at label dose and assigned to one of four PMEP (3-, 5-, 7- or 10-days) groups (n=140 per treatment). Morbidity caused by BRD was reduced ( P <0.05) in all tilmicosin metaphylaxis groups compared to controls (55.7, 56.4, 52.1, 39.3 and 69.3% for the 3-, 5-, 7- and 10-day PMEP groups and controls, respectively). The morbidity rate due to BRD was lower ( P <0.01) in the 10-day PMEP group compared to other PMEP groups, however, mortality in this group was numerically higher than the other PMEP groups. There was no difference in ADG among treatments. Calves diagnosed with clinical BRD following the PMEP and control calves showing signs of BRD were treated with tulathromycin (1.14 mg/lb; 2.5 mg/kg BW) in both studies. Treatment success was similar across all treatments in each study, but was numerically higher in Study I (88.0%) compared to Study II (66.8%).