Influence of yeast cell wall supplementation during the finishing phase on feedlot steer performance, carcass characteristics, and postmortem tenderness

Our objectives were to evaluate the benefits of yeast cell wall (YCW) supplementation on performance, carcass characteristics, and tenderness of steers finished with zilpaterol hydrochloride. A randomized complete block design was used. British × Continental steers (n = 72; initial BW = 305 ± 13 kg) were blocked by BW and allotted randomly to 24 pens (8 pens per treatment; 3 pens per block; 3 steers per pen). Treatments were (1) control (CON); (2) YCW containing 100,000 IU of vitamin D₂ per gram (5.0 g per steer per d; Y-D); (3) YCW C (5.0 g per steer per d; Y-C). Steers were supplemented 55 d, and zilpaterol hydrochloride was fed on d 30 to 49. Carcass data and strip loins were obtained. Strips were cut into steaks and assigned to 1 of 4 aging periods (7, 14, 21, or 28 d). Tenderness was examined using Warner-Bratzler shear force. Carcass-adjusted ADG from d 21 to 55 was 0.29 kg greater for Y-D and 0.35 kg greater for Y-C, when compared with CON (P = 0.04 and 0.01, respectively). Additionally, YCW increased G:F from d 21 to 55 by 28.46% for Y-C over CON (P = 0.01). Treatment Y-C displayed Warner-Bratzler shear force values 0.30 kg higher than CON and 0.29 kg greater than Y-D (P < 0.01). Within 7 d of aging, Y-C steaks were 0.62 kg (P = 0.005) and 0.54 kg (P = 0.014) less tender than CON or Y-D, respectively. For 14 d of aging steaks, Y-C Warner-Bratzler shear force values were 0.58 kg greater than CON (P = 0.008). These data indicate YCW supplementation could improve performance of finishing steers, and vitamin D₂ supplementation at the current dosage did not improve tenderness.