The effects of administering different metaphylactic antibiotics on growth performance and health outcomes of high-risk, newly received feedlot cattle
Bovine respiratory disease (BRD) is one of the biggest problems facing producers when calves enter the feedlot. While there are many antimicrobial mitigation strategies available, studies comparing multiple antimicrobials over the entirety of both receiving and finishing period are novel. The objective of this study was to determine the most effective metaphylaxis antimicrobial on reducing morbidity and mortality and improving growth performance across both the receiving and finishing period. A total of 238 multiple-sourced steers in 2 source blocks were used in a generalized complete block design. The 4 treatments included: 1) a negative control, 5 mL of sterile saline injected subcutaneously (CON); 2) subcutaneous administration of florfenicol (Nuflor; Merck Animal Health) at 40 mg/kg of BW (NUF); 3) subcutaneous administration of ceftiofur in the posterior aspect of the ear (Excede; Zoetis, Parsippany, NJ) at 6.6 mg/kg of BW (EXC); and 4) subcutaneous administration of tulathromycin (Draxxin; Zoetis) at 2.5 mg/kg of BW (DRA). The morbidity rate for the first treatment of BRD was decreased for the DRA and EXC treatments compared to NUF and CON treatments (P< 0.01). Additionally, average daily gain (ADG), dry matter intake (DMI) and gain to feed (G:F) were increased (P ≤ 0.02) in the DRA treatment during the receiving period. The ADG was greater (P < 0.05) for EXC than the CON treatment throughout the finishing period. Nonetheless, the other performance variables did not differ among treatments during the finishing period (P ≥ 0.14). The results indicate that some commercially available products are more efficacious than others for reducing morbidity rate, but they do not improve overall growth performance.