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Influence of Calcium Depletion and Repletion on Beef Tenderness of Steers fed Zilpaterol Hydrochloride
Influence of Calcium Depletion and Repletion on Beef Tenderness of Steers fed Zilpaterol Hydrochloride
J. O. Carothers*1, D. N. Burton, K. R. Underwood, and R. H. Pritchard. 1South Dakota State University, Brookings
The objective of this study was to evaluate the influence of manipulating dietary Ca to influence tenderness via the calpain system in steers fed zilpaterol HCl (ZIL). Steers (n=120; BW 478 ± 18 kg) were blocked by BW, and randomly assigned to 1 of 3 treatments 50 d prior to initiating dietary treatments. Dietary Treatments included: 1) Control, conventional finishing diet (sans ZIL); 2) Control diet plus ZIL (6.78 g/T) fed for 20 d; and 3) depleted dietary Ca while feeding ZIL. Cattle on treatments 2&3 were changed to diet 1 for 3 d prior to harvest which restored dietary Ca for cattle on treatment 3 and accommodated ZIL withdrawal requirements. A subsampleof steers were taken to quantify serum Ca levels and shear force values for strip loins and sirloin butts. Blood was collected from the subsample 24 h prior to harvest (48 h after cattle treatment 2&3 switched to diet 1). Muscles were cut into steaks and aged 14 d. Orthogonal contrasts were used to compare control vs. ZIL (treatment 1 vs. 2&3) and Ca manipulations (treatment 2 vs. 3). Feeding ZIL caused increased (P<0.05) BW (610 vs. 620 kg), ADG (1.32 vs. 1.66 kg), and G:F (116 vs. 152 g/kg) compared to control. Zilpaterol increased (P<0.05) HCW (373 vs. 392 kg), dressing percentage (63.08 vs. 65.10%) and LMA (82.26 vs. 91.52 cm2) but did not affect (P>0.05) marbling score (Small73 vs. Small55) when compared with control. Calcium manipulation did not affect (P>0.05) live or carcass variables or serum Ca levels (10.6 vs. 11.0 mg/dl). Zilpaterol increased WBSF values (P<0.05) for 14 d aged strip steaks (5.28 vs. 6.99 kg), while having no effect (>0.05) on shear force values for sirloin butts (6.24 vs. 6.83 kg). Dietary Ca manipulations did not affect (P>0.05) shear force values. Manipulating dietary Ca did not adversely affect live performance or carcass traits. Prolonged repletion (3 d) may have been too long to allow for influences on the calpain system to affect tenderness.
Keywords: beef, zilpaterol, tenderness