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Interaction of various inclusion levels of dietary vitamin D2 enriched yeast cell wall with zilpaterol hydrochloride on dry matter intake and post mortem tenderness in feedlot steers
The objectives of this study were to examine the impact of various inclusion rates of vitamin D2 enriched yeast cell wall (YCW) on performance and carcass characteristics of cattle finished with zilpaterol hydrochloride (ZH). Crossbred steers (n = 192; BW = 546 ± 11 kg) were blocked by BW in a randomized block design and randomly assigned to pen (6 pens/block; 4 hd/pen). Pens within block were assigned to one of six treatments (8 pens/treatment): 1) negative control (-CON; no ZH, no YCW), 2) positive control (+CON; ZH, no YCW), 3) vitamin D2 YCW containing 100,000 IU vitamin D2/gram (2.5 g/hd/d), 4) vitamin D2 YCW (5.0 g/hd/d), 5) vitamin D2 YCW (10.0 g/hd/d), 6) YCW C-wall product (2.5 g/hd/d). Steers were supplemented with respective treatments for the 51 d duration of the trial, of which ZH was supplemented d 28-47. Daily DMI was recorded and BW was collected at d 0, 28, and 51. Carcass data was collected upon harvest and ten choice strip loins were randomly collected from each treatment for further analysis. Strips were cut into steaks and assigned to one of four aging periods (7, 14, 21, 28 d). Tenderness was estimated using Warner-Bratzler shear force (WBSF). Data were analyzed using a randomized block design with the fixed effect of treatment and the random effect of block. Warner-Bratzler shear force values were analyzed using the same model, including aging period as an additional factor. Dry-matter intake showed a significant quadratic relationship (P = 0.01) for increasing levels of D2 YCW for the entire feeding period, with the greatest intake in the 10.0 g treatment (10.30, 10.27, and 10.66 kg/d respectively). All ZH fed treatments had numerically greater WBSF values than negative control, but values among ZH treatments were insignificant across all aging periods. There was a tendency for lower WBSF values in the 10.0 g D2 YCW treatment when compared to positive control (P = 0.10, 0.06, 0.10, and 0.09), and WBSF values of steaks from the 10.0 g YCW treatment ranged from 0.44 (d 21) to 0.69 (d 7) kg lower than positive control for all aging periods. Results indicate that yeast cell wall supplementation could increase performance of finishing steers during ZH supplementation, while vitamin D2 supplementation may have positive effects on tenderness.
Keywords: Vitamin D, yeast, zilpaterol hydrochloride