A randomized trial comparing the effects of tulathromycin, tildipirosin and gamithromycin used as first treatment for clinical bovine respiratory disease in commercial feedlot steers

Abstract

Our objective was to compare effects of 3 macrolide antibiot­ics used as first-time bovine respiratory disease (BRD) treat­ment on primary health outcomes (retreatment, removal and mortality) in feedlot steers. Secondary outcomes included days-on-feed, rectal temperature and weight at the time of event occurrences. Crossbred beef steers (n = 978; average body weight [± SD] 655 ± 84.0 lb [297 ± 38.1 kg]) were enrolled across 2 commercial feedlots in the U.S. High Plains in a ran­domized complete block design. Steers were eligible for in­clusion if they were exhibiting clinical BRD symptoms from natural exposure and had not been previously treated with an antimicrobial drug for any reason including metaphylaxis. Treatment was administration of tulathromycin, tildipirosin or gamithromycin, at the time of first BRD diagnosis. Linear and generalized linear mixed models were used for statisti­cal analyses with significance threshold α = 0.05. At enroll­ment, animal weight (P = 0.98), rectal temperature (P = 0.58), and days-on-feed (P = 0.28) did not differ significantly between treatments. There was no evidence of differences for any health outcome (P ≥ 0.30), nor for any cattle characteristics at the time of retreatment, removal, or mortality (P ≥ 0.15). Treatment success (steers that were never retreated, removed, and/or were a BRD case fatality) ranged from 62.7 to 64.8% between treatments (P = 0.87). There was no evidence to reject the null hypothesis of similar effectiveness between these macrolides when administered to similar steer populations as first-time clinical BRD treatments.