Decreasing Dietary Calcium to Potentiate Changes in Beef Tenderness with Zilpaterol Hydrochloride Supplementation

Abstract Text: Dietary calcium concentrations were manipulated during supplementation of zilpaterol hydrochloride (ZH) to evaluate impact on feedlot performance, carcass characteristics, and beef tenderness using 96 heifers (BW 392 kg ± 3.2). We hypothesized that temporary depletion followed by repletion of dietary calcium prior to harvest would increase intracellular calcium concentrations, thus stimulating postmortem activity of calcium-dependent proteases. Heifers were stratified by initial BW and randomly assigned, within strata (block), to treatments consisting of a finishing diet in which calcium was added in the form of limestone (+Ca) and a diet in which the limestone had been removed (-Ca) during ZH supplementation. Cattle were fed a common diet prior to ZH supplementation, and 24 d prior to slaughter ZH was added to the diet with and without the supplemental calcium. Calcium content of the diets during ZH supplementation was 0.74% or 0.19% (diet DM) for +Ca and -Ca, respectively. Zilpaterol hydrochloride was fed for 21 d then removed from the diet 3 d prior to harvest. The final 3 d before harvest limestone was added back into the -CA diet at 0.74% of diet DM. Heifers were housed in concrete surfaced pens with 8 animals per pen (6 pens per treatment). At the end of the finishing phase animals were weighed and shipped to an abattoir in Holcomb, Kansas. Severity of liver abscesses and HCW were collected the day of harvest, and after a 48-h chill USDA yield and quality grades, KPH, LM area, 12^th rib fat thickness were determined and boneless loin section was collected for Warner-Bratzler shear force determination. Removal of calcium did not affect Warner-Bratzler shear force values (P = 0.64). In addition, ADG, DMI, final BW and feed efficiency were unaffected by treatment (P > 0.05). Carcass measurements also were unaffected by the decrease in dietary calcium (P > 0.05). In conclusion, temporary depletion of dietary calcium did not alter beef tenderness, live animal performance, or carcass measurements. 

Keywords: calcium, zilpaterol hydrochloride, beef tenderness