Effect of vitamin D2 enriched yeast cell wall supplementation on growth performance, carcass characteristics, and postmortem tenderness in feedlot steers finished with zilpaterol hydrochloride1

The objectives of this experiment were to evaluate the effects of vitamin D2 enriched yeast cell wall (YCW) inclusion rate in zilpaterol hydrochloride (ZH) supplemented beef cattle on feedlot performance, carcass characteristics, and postmortem tenderness. A total of 160 crossbred beef steers (BW = 527 ± 10 kg) were blocked by BW (8 blocks; 5 pens per block; 4 steers per pen) and randomly assigned to 1 of 5 treatments: a control diet with no ZH or YCW, or 1 of 4 treatments receiving ZH in addition to YCW (100,000 IU vitamin D2/g) at rates of 0, 2.5, 5.0, and 10.0 g/d per steer. After the 51-d duration of the treatment period, cattle were slaughtered and carcass data were collected. Ten USDA Choice strip loins were randomly selected from each treatment, cut into 2.54-cm-thick steaks, and assigned to 4 aging periods (7, 14, 21, and 28 d). Steaks were subsequently analyzed for tenderness using Warner-Bratzler shear force. Dry matter intake responded quadratically (P = 0.01) to increasing levels of YCW inclusion; however, ADG (P = 0.11) and G:F (P = 0.60) were not different. There was a linear decrease (P = 0.01) in DP and a corresponding linear increase (P = 0.02) in KPH as YCW inclusion was increased. All other carcass characteristics were unchanged. Shear force values for vitamin D2 YCW supplemented treatments tended to be reduced at 14 d (P = 0.09), and Warner-Bratzler shear force values for steaks from cattle supplemented with 10 g/d per steer of vitamin D2 enriched YCW were the lowest of all ZH supplemented cattle across all age periods. These data suggest that YCW inclusion may negatively affect carcass yield; however, high levels of vitamin D2 YCW inclusion may positively affect tenderness qualities of meat from ZH finished cattle.