150 Supplementing Bovacillus to high-risk cattle during a 90-d grazing period

Abstract This experiment compared performance, health, and physiological responses of high-risk beef cattle receiving a Bacillus-based probiotic during a 90-d grazing period in a study replicated over 2 yr. Angus-influenced steers (n = 120/yr) were obtained from an auction yard and transported to the experimental facility (150 km). Steer body weight (BW) was recorded at arrival (d -1), and this value was averaged with BW recorded on d 0 to represent initial BW (236. 6 ± 1. 5 kg). On d 0, steers were ranked by BW and allocated to 1 of 12 pastures (4-ha pastures; 10 steers/pasture). Pastures were randomly assigned to receive daily supplementation with dried distillers grains at 1% of BW containing either: 1) Bacillus subtilis and B. licheniformis ingredient (BOV; 2 g/steer daily of Bovacillus; Novonesis, Horsholm, Denmark) or 2) no additive (CON). Cattle received treatments from d 0 to 90 while housed in pastures containing stockpiled native grass forage, as well as free-choice access to water and a commercial mineral + vitamin mix without ionophores. Steers were assessed for bovine respiratory disease (BRD) signs daily. Blood samples were collected, and BW recorded on d 0, 14, 28, 56, and 90. Shrunk BW was recorded on d 91 for average daily gain calculation. No treatment differences were detected (P ≥ 0. 36) for glucose, non-esterified fatty acids, β-hydroxybutyrate, insulin-like growth factor-1, or plasma concentrations of antibodies against BRD viruses. A treatment × day interaction was detected (P ≤ 0. 05) for plasma haptoglobin concentration, which was greater for CON steers on d 14 and 28 (P ≤ 0. 02). Although BRD incidence response lacked treatment differences (P = 0. 97), steer mortality and removals for health complications were greater in CON compared with BOV steers (0. 00 vs 5. 04 %; P = 0. 01). Body weight and average daily gain were not impacted by BOV supplementation (P ≥ 0. 73). Total BW gain per pasture was greater in BOV compared with CON (643 vs. 496 kg BW change/pen; P = 0. 02). Overall profit per pasture was increased in BOV steers compared with CON (29. 1 vs -330; P = 0. 03) resulting in a return on investment of 33: 1 over the 90-d experimental grazing period. Despite lacking difference for incidences of BRD or most physiological responses, an increased number of BOV steers completed the trial. Hence, supplementation with a probiotic based on B. subtilis and B. licheniformis to high-risk beef steers increased overall production liveweight and investment return during a 90-d grazing period.