241 Trends in the percentage of modified live, killed, and combination respiratory viral vaccines administered to beef calves offered for sale in summer video auctions from 2000 through 2018

Abstract The objective of this study was to identify trends in the percentage of type of respiratory viral vaccines administered to lots of beef calves offered for sale in summer video auctions from 2000 through 2018. There were 59,762 lots of single-gender beef calves (7,167,352 total calves) offered for sale in 145 summer video auctions during these years. Information describing calf lots was obtained from the auction service (Superior Livestock Auction, Fort Worth, TX) which included named vaccines administered to the lot. Named 4- or 5-way respiratory viral vaccines were classified into three groups based on the type of antigens they contained: all modified live antigens (MLV), all killed antigens (KILLED), and a combination of modified live and killed antigens (COMBO). The Cochran-Armitage Trend Test was used to quantify the significance of a trend in the usage of each respiratory viral vaccine type. There was an increase (P < 0.0001) in the percentage of MLV vaccines given to beef calf lots from 2000 (39.7%) through 2018 (88.9%). At the same time, the percentages of both KILLED and COMBO vaccines administered to lots of beef calves declined (P < 0.0001 and P < 0.0001, respectively). In 2000, 31.2% and 29.1% of the total respiratory viral vaccines given to beef calf lots were KILLED or COMBO vaccines, respectively. By 2018, only 4.7% of respiratory viral vaccines were KILLED, and only 6.4% were COMBO vaccines. This dramatic shift indicates an industry trend towards increasing MLV vaccine utilization compared with declining usage of KILLED and COMBO vaccines. This trend may be a result of MLV vaccine approval for use in calves nursing pregnant cows.