Abstract
Forty-eight newly weaned crossbred beef steers from a single-source were used to determine the effects of feeding a Saccharomyces cerevisiae fermentation product (SCFP; NaturSafe, Diamond V) on receiving period performance, nutrient digestibility, and antioxidant defense. Seven days after arrival, steers were stratified by BW (257 ± 18 kg), sorted into pens (n = 1 pen/treatment), and pens assigned to dietary treatments: SCFP at 0 (CON), 12 (SCFP12), 18 (SCFP18), or 0 g·steer-1·d-1 during preconditioning (PRE; days -19 to 0), then 18 g·steer-1·d-1 during receiving (REC; days 0 to 58; CON18). On day -1 BW and blood were collected, steers were loaded onto a semitruck and transported 1,748 km over 19 h. Upon return, steers were weighed, stratified by BW within treatment and sorted into pens with GrowSafe bunks (n = 12 steers/treatment). Steers were weighed on days -1, 0, 29, 30, 57, and 58. Blood was collected from all steers on days -1, 1, and 8 and liver biopsies were performed on all steers on days -20, -3, and 59. Titanium dioxide was included as an indigestible marker in the diet of all steers from days 14 through 29 to determine total tract nutrient digestibility. Data were analyzed as a completely randomized design using ProcMixed of SAS with the fixed effect of treatment. Steer was the experimental unit for REC period variables. Contrast statements compared the linear and quadratic effects of feeding SCFP throughout the trial (CON, SCFP12, and SCFP18) and the effect of supplementation at 18 g·steer-1·d-1 for the entire trial or starting in REC (SCFP18 vs. CON18). Steers fed SCFP12 exhibited the greatest ADG and G:F from days 0 to 30 (quadratic P ≤ 0.04). Total tract digestibility of NDF and ADF was linearly decreased by SCFP (linear P ≤ 0.03). On day -3, SCFP12-fed steers tended to have the greatest liver concentrations of total, oxidized, and reduced glutathione (quadratic P = 0.06). Red blood cell lysate Mn:total-superoxide dismutase activity was 16% greater 1 d posttransit compared with pretransit values (day P ≤ 0.01). Timing of SCFP supplementation (SCFP18 vs. CON18) did not affect any of the variables assessed herein (P ≥ 0.19). Supplementing SCFP at 12 g·steer-1·d-1 tended to affect antioxidant capacity prior to transit and improved early receiving period performance; however, overall receiving period performance was not affected by SCFP supplementation. Further research is necessary to determine the optimal dose and timing of SCFP supplementation for beef cattle.