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, NATE - Texas Tech University; HOFFMAN, ASHLEY - Texas Tech University; Carroll, Jeffery; Broadway, Paul; Sanchez, Nicole; Wells, James; FERNANDO, SAMODHA - University Of Nebraska; HALES, KRISTIN - Texas Tech University

Submitted to: Proceeding of Plains Nutrition Council Symposium
Publication Type: Abstract Only
Publication Acceptance Date: 3/31/2022
Publication Date: 4/13/2022
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. Proceedings of the Plains Nutrition Council Spring Conference. p. 194.

Interpretive Summary:

Technical Abstract: The objective of this experiment was to compare methods of antimicrobial metaphylaxis on clinical health and growth performance outcomes during feedlot receiving and finishing periods. Multiple-sourced steers (n = 238) were used in a generalized complete block design consisting of 2 arrival date blocks, 6 treatment replications during the receiving period, and 15 treatment replications during the finishing period. Pen was the experimental unit for all dependent variables. Experimental treatments were: 1) negative control, 5 mL subcutaneous sterile saline; 2) subcutaneous administration of florfenicol, 40 mg/kg BW (NUF); 3) administration of ceftiofur in the posterior aspect of the ear, 6.6 mg/kg BW (EXC); or 4) subcutaneous administration of tulathromycin, 2.5 mg/kg BW (DRA). Both DRA and EXC decreased first BRD morbidity compared to NUF and CON (P < 0.01). Likewise, ADG, DMI, and G:F were greatest in DRA during the receiving period (P = 0.02), however, these observations were not substantiated throughout the finishing period on both a live and carcass-adjusted basis (P = 0.12). Additionally, no differences in carcass characteristics or liver abscess score were observed (P = 0.18). All CBC variables were affected by day (P = 0.01) except mean corpuscular hemoglobin concentration (P = 0.29). Treatment × time interactions observed for platelet count, WBC count, monocyte count and percentage, and lymphocyte percentage (P = 0.03). Nonetheless, all observed hematological values fell within normal ranges for cattle. The results of this work indicate that metaphylaxis with tulathromycin or ceftiofur effectively improved clinical health outcomes of high-risk calves, and that feedlot production metrics are similar overall among differing drugs evaluated.