Comparative efficacy of metaphylaxis with tulathromycin and pentavalent modified-live virus vaccination in high-risk, newly received feedlot cattle

ABSTRACT Objective 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 and their influence on health and growth performance during a 56-d receiving period. Materials and Methods Beef bulls (n = 372) and steers (n = 106) were 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 (CON), (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 per treatment. Body weight and feed refusals were recorded periodically to determine interim and overall (d 0 to 56) performance and feed efficiency. A subset (n = 256) was affixed with a 3-axis accelerometer ear-tag to quantify activity and rumination time. A 7-d postmetaphylactic interval was implemented for META, and bovine respiratory disease cases were determined by treatment-blinded, trained investigators. Results and Discussion The META groups had greater ADG from d 0 to 14, from d 14 to 28, and overall (P ≤ 0.01) and BW on d 56 was increased (P Implications and Applications Health and performance of high-risk feedlot cattle was improved by META but not MLV.