Feedlot performance and carcass characteristics of steers managed with growth-promoting technologies while grazing toxic, endophyte-infected fescue during autumn and winter months

Objective: Our objective was to evaluate subsequent feedlot performance and carcass characteristics of steers that previously grazed endophyte-infected fescue and received either a mineral only (MIN) supplement or a cumulative management (CM) strategy. Materials and Methods: Grazing occurred in autumn and winter of 2018 and 2019 with feedlot finishing after grazing. Within year, 60 fall-weaned steers (282 +/- 7.7 kg) were randomly assigned to either MIN (n = 3) or CM (n = 3) pastures. The CM strategy include a steroidal growth implant, monensin, and 1% BW (as-fed basis) of 1:1 corn gluten feed: soybean hull mix. During feedlot finishing, steers were penned to maintain pasture groups. Results and Discussion: Steers receiving CM were heavier (P = 0.002) entering the feedlot and finished 40 d earlier than MIN (161 vs. 201 +/- 5.7 d, P < 0.001). The CM steers gained more BW the first 28 d (P = 0.005) in the feedlot. Both treatments showed similar overall ADG (P >= 0.23), but MIN steers showed a tendency for greater G:F (P = 0.06). Finished live weight and carcass traits did not differ (P >= 0.18). Pens were 78 and 80 +/- 5.4% USDA Choice for MIN and CM, respectively. Implications and Applications: A CM strategy increases weight of steers grazing toxic fescue. This additional weight can reduce the days required for feedlot finishing without influencing carcass characteristics. Improved grazing performance and fewer days for feedlot finishing may reduce environmental impact.