Comparison of three injectable metaphylactic antimicrobial treatments administered at feedlot arrival for control of bovine respiratory disease in calf-fed Holstein steers
Three injectable metaphylactic antimicrobials were evaluated for efficacy against bovine respiratory disease (BRD) in calf-fed Holstein steers. Calves (N=3,605) weighing between 210 and 580 lb (95 and 263 kg) were enrolled in a complete random study design and administered either tulathromycin (TUL, 1.1 mL/100 lb [45.4 kg] of body weight [BW]), tildipirosin (TPR, 1.0 mL/100 lb [45.4 kg] BW), or gamithromycin (GAM, 1.8 mL/100 lb [45.4 kg] BW) at feedlot arrival. Body weight, health events, and carcass data were collected to assess differences among experimental groups for morbidity, mortality, treatment success, realizer rate, average daily gain (ADG), and carcass traits. An economic model was developed to compare the relative economic outcome associated with metaphylaxis using parameters describing morbidity, relapse, realizer, and mortality rates as well as the individual drug cost. No significant differences (P>0.05) were observed for ADG, first-pull morbidity rate, mortality rate, carcass weight, backfat, or marbling score due to metaphylaxis across experimental groups. Calves administered gamithromycin at processing had a significantly lower (P=0.01) realizer rate and realizer plus mortality rate, and higher (P=0.02) first-treatment success rate compared to calves administered tulathromycin. Health and performance outcomes did not differ between calves in the GAM and TPR groups; however, drug cost was lower in the GAM group. Compared to calves in the TUL group, the economic benefit of metaphylaxis was greater for calves in the GAM experimental group when considering drug cost and difference in relapse, realizer, and realizer plus mortality rates.