Comparative Efficacy of Metaphylaxis and Respiratory Vaccination in High-Risk, Newly Received Feedlot Cattle

Abstract

Our objective was to compare metaphylaxis with tulathromycin (META) and vaccination with a pentavalent modified-live virus respiratory vaccine (MLV) in high-risk feedlot calves. Beef bulls (n = 372) and steers (n = 106) were blocked by truck load, stratified by initial BW (234 ± 1.32 kg), health status and sex, and randomly assigned to treatments arranged in a 2 × 2 factorial: 1) no META or MLV; 2) META administration on d 0 (META), 3) MLV administration on d 0 with revaccination on d 14 (MLV), and 4) META and MLV administration (META+MLV). Interactions and main effects were analyzed within a generalized complete block design using a mixed statistical model with 10 pen replicates/treatment. Body weight and feed refusals were recorded on d -1, 0, 14, 28, 55 and 56 to determine interim and overall (d 0 to 56) gain performance, dry matter intake, and gain to feed ratio. A subset (n = 256) was affixed with a 3-axis accelerometer ear-tag to quantify activity and rumination time. A 7-d post-metaphylactic interval was implemented for META and BRD cases were determined by treatment-blinded, trained investigators. Interactions were tested first, followed by the main effects of META and VAC if the interaction for a given dependent variable was non-significant (P > 0.05). The META groups had greater ADG from d 0 to 14, 14 to 28, and overall (P ≤ 0.01). Body weight on d 14, 28, and 56 was increased (P < 0.01) for calves in the META group with a 13.52 kg increase on d 56. For each interim period and overall, DMI was greater (P < 0.01) for META, but not MLV (P ≥ 0.11). The BRD morbidity rate was less for META (18.5 vs. 51.2%; P < 0.01); however, it was not improved for MLV (P = 0.37). Increased daily rumination time was observed for META (P < 0.05). A META × day interaction existed (P = 0.01) for daily rumination time and greater rumination minutes occurred for META groups from d 9 to 20 and on d 22, 24, 26, 27, and 29 (P < 0.05). Health and performance of high-risk feedlot cattle was improved by META, but not MLV.