Supplementing a Bacillus-based probiotic to high-risk stocker cattle.

ABSTRACT

This experiment evaluated the performance, health, and physiological responses of high-risk steers receiving a Bacillus-based probiotic during a 90-d grazing period. A total of 240 Angus-influenced steers were used in this experiment that was replicated over 2 yr (120 steers/year). Each year, steers were obtained from an auction yard and transported to the experimental facility (120 km). Steer body weight (BW) was recorded at arrival (day -1), and this value was averaged with BW recorded on day 0 to represent the initial BW (236.6 ± 1.5 kg). On day 0, steers were ranked by BW and allocated to 1 of 12 pastures with stockpiled native grass (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 + B. licheniformis probiotic (BOV; 2 g/steer daily of Bovacillus; Novonesis, Horsholm, Denmark) or 2) no feed additive (CON). Cattle received treatments from days 0 to 90, in addition to free-choice access to water and mineral + vitamin mix without ionophore. Steers were assessed for bovine respiratory disease (BRD) signs daily. Blood samples were collected and full BW was recorded on days 0, 14, 28, 56, and 90. Shrunk BW was recorded on day 91 after 16 h of feed and water restriction, and a 4% pencil shrink was used to calculate the final BW. Average daily gain (ADG) was calculated based on initial and final BW. No treatment effects were detected (P ≥ 0.73) for steer final BW and ADG. A treatment × day interaction was detected (P ≤ 0.05) for plasma haptoglobin concentration, which was greater for CON steers on days 14 and 28 (P ≤ 0.02). Incidence of BRD signs did not differ (P = 0.97) between treatments (51.7% and 51.3% for BOV and CON, respectively; SEM = 7.70). However, steer mortality + removals for health complications were greater (P = 0.01) in CON compared to BOV (0.00% vs. 5.04%, respectively; SEM = 1.41). Supplementing BOV improved (P ≤ 0.04) total pasture-based liveweight change (643 vs. 502 kg/pasture, respectively; SEM = 45) and final pasture-based total liveweight (3,007 vs. 2,869 kg/pasture, respectively; SEM = 46). Collectively, supplementation with a probiotic based on B. subtilis and B. licheniformis to high-risk stocker cattle did not alleviate the incidence of BRD signs nor improved ADG, but decreased acute-phase protein response, reduced steer mortality + removal, and increased pasture-based productivity during a 90-d grazing period.

Stocker cattle are exposed to several stressors within a short period of time, which impair their immunity and lead to bovine respiratory disease (BRD). With the increased regulations regarding the use of antimicrobials in cattle nutrition, novel dietary strategies to improve health and productivity of stocker cattle are warranted. One example is supplementing Bacillus-based probiotics, which promote performance and immunity in high-stress cattle. In this study, steers were purchased from a commercial auction yard soon after weaning, transported to the research facility, and assigned initial processing within a 48-h period. Steers were assigned to pastures and were supplemented or not with the Bacillus-based probiotic during a 90-d grazing period. In general, supplementing steers with the Bacillus-based probiotic did not impact growth rates or BRD incidence. However, no steers that received the Bacillus-based probiotic died from BRD consequences nor were removed from the experiment due to health reasons, whereas 5% of unsupplemented steers did not complete the 90-d experiment. Consequently, pasture-based liveweight gain was increased by 28% due to Bacillus-based probiotic supplementation. Results from this study indicate that supplementing a B. subtilis + B. licheniformis probiotic could be an alternative to improve the health and overall productivity of high-risk stocker cattle.