Effect of Enhanced Management on Behavior of Calves Grazing Tall Fescue of Varied Toxicity Levels

The experimental objective was to evaluate the behavior of steers grazing tall fescue (Festuca arundicea) with low- to high- toxicity levels at different levels of growth promotion management (MGMT) using accelerometers. Steers (n = 80; BW = 116.93 ± 4.9 kg) grazed pastures (n = 16, 1.2 ha pastures) during the spring grazing season from 22 March to 14 June for 84 d in 2016 at a stocking rate of 4.1 steers/ha. Accelerometers were placed on 3 steers in 15 pastures from 21 April to 17 May (Period 1) and from 17 May to 12 June (Period 2). Steers on eight pastures were fed a control mineral (MIN) with no additional growth promotion. Steers on 7 pastures were managed with cumulative growth promotion management (CM) which included a growth promoting implant (TE-G with Tylan, Elanco Animal Health, Greenfield, IL) and 1% of BW of a 50:50 corn gluten feed:soybean hull pellet containing monensin at 150 mg per calf (Rumensin, Elanco Animal Health) fed daily. Ergovaline (EV) concentrations were analyzed in each pasture resulting in a range of EV from 90 ppb to 2,180 ppb. Data were analyzed using management (MIN vs CM), EV concentration, period, and the two and three-way interactions. Reduced models were applied in case of non-significant interactions in the full models. Motion index decreased (P = 0.04) with EV but increased (P < 0.01) with CM compared with MIN. Total steps (TS) increased (P < 0.01) for CM compared with MIN, while TS decreased with increasing EV (P < 0.01). Total standing minutes were less (P < 0.01) for CM than MIN during Period 2. Lying bouts were not affected (P ≥ 0.22) by EV or MGMT during Period 1. Lying bouts were greater (P < 0.01) for CM than MIN in Period 2 and increased with increasing (P = 0.02) EV during Period 2. An EV by MGMT interaction (P = 0.02) during Period 2 indicates that with CM, lying bouts decreased (P = 0.02) with increasing EV, but increased (P = 0.02) lying bouts in MIN. The changes in behavior between periods indicate that EV concentration decreases total steps taken but will change behavior from standing to lying with higher environmental temperatures. Feeding high supplementation rates with the CM treatment increased minutes spent standing during Period 1 and decreased lying bouts in Period 2, this increased activity with CM occurred regardless of environmental temperatures.