The effects of administering different metaphylactic antimicrobials on growth performance and health outcomes of high-risk, newly received feedlot steers

Authors: COPPIN, CARLEY - Texas Tech University; SMOCK, TAYLOR - Texas Tech University; HELMUTH, CORY - Texas Tech University; MANAHAN, JEFF - Texas Tech University; LONG, NATHAN - Texas Tech University; HOFFMAN, ASHLEY - Texas Tech University; Carroll, Jeffery - Jeff Carroll; Broadway, Paul; Sanchez, Nicole; Wells, James - Jim; FERNANDO, SAMODHA - University Of Nebraska; HALES, KRISTIN - Texas Tech University

Submitted to: Translational Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/18/2022
Publication Date: 10/15/2022
Citation: Coppin, C.M., Smock, T.M., Helmuth, C.L., Manahan, J.L., Long, N.S., Hoffman, A.A., Carroll, J.A., Broadway, P.R., Sanchez, N.C., Wells, J., Fernando, S.C., Hales, K.E. 2022. The effects of administering different metaphylactic antimicrobials on growth performance and health outcomes of high-risk, newly received feedlot steers. Translational Animal Science. 6(4). Article txac140. https://doi.org/10.1093/tas/txac140.
DOI: https://doi.org/10.1093/tas/txac140

Interpretive Summary: Bovine respiratory disease (BRD) is complex disease that affects 16.2% of U.S. feedlot cattle. As preventative measure, many beef feedlots try to reduce this illness by treating incoming high-risk cattle with antimicrobial drugs. Therefore, scientists from Texas Tech University and ARS' Livestock Issues Research Unit collaborated on a study to evaluate how common antimicrobial drugs used for this purpose affect important feedlot production parameters during both the receiving and finishing periods. Results indicated that cattle administered tulathromycin or ceftiofur at feedlot arrival were subsequently treated for BRD fewer times than those administered florfenicol or the negative control. Likewise, cattle administered tulathromycin had improved growth performance during the receiving period. However, these differences were not observed during the finishing period or when considering the overall feedlot period. Thus, no further differences in growth performance or carcass characteristics were observed. Overall, this work indicates that antimicrobial treatment with tulathromycin or ceftiofur is effective for improving clinical health outcomes of high-risk calves. Also, feedlot production parameters are similar overall among the different drugs evaluated. This data will be of interest to beef feedlot producers, veterinarians, and beef cattle scientists.

Technical Abstract: Bovine respiratory disease is the primary animal health concern facing feedlot producers. Many antimicrobial mitigation strategies are available, but few studies have compared feedlot performance during both the receiving and finishing periods following differing antimicrobials used as metaphylaxis at arrival. The objective of this study was to compare antimicrobial metaphylaxis methods on clinical health and growth performance across both the receiving and finishing periods. 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 at 40 mg/kg of BW (NUF); 3) subcutaneous administration of ceftiofur in the posterior aspect of the ear at 6.6 mg/kg of BW (EXC); and 4) subcutaneous administration of tulathromycin 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 (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, growth performance variables did not differ among treatments during the finishing period (P = 0.14) or on a carcass-adjusted basis (P = 0.12). Likewise, no differences in carcass characteristics or liver abscess score were observed (P = 0.18). All complete blood count (CBC) variables were affected by day (P = 0.01) except mean corpuscular hemoglobin concentration (P = 0.29). There were no observed treatment differences among CBC variables (P = 0.10). However, treatment x time interactions were observed for platelet count, white blood cell (WBC) count, monocyte count and percentage, and lymphocyte percentage (P = 0.03). The results indicate that some commercially available antimicrobial drugs labeled for metaphylactic use are more efficacious than others in reducing morbidity rate, but overall growth performance and final carcass outcomes were not different.