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Document Type

Thesis - University Access Only

Award Date


Degree Name

Master of Science (MS)

Department / School

Animal Science

First Advisor

Robbi Prichard


beef, calcium manipulation, zilpaterol, shearforce


These studies evaluated the influence of manipulating dietary Ca on tenderness via the calpain system in steers fed zilpaterol hydrochloride (zilpaterol). In Exp. 1, steers (n=120; BW 478 ± 18 kg) were blocked by BW and assigned to 1 of 3 treatments: a Control diet (CON); the Control diet plus 6.78 g/T Zilpaterol (ZIL); and a zilpaterol supplemented diet with calcium carbonate removed from the supplement (ZIL-Ca). Test diets were fed for 20 d, then cattle on ZIL and ZIL-Ca were changed to CON to accommodate the labeled zilpaterol withdrawal requirement (3 d) and to restore dietary Ca. Sentinel steers were sampled to quantify serum Ca levels 48 h after realimentation. Strip loins and sirloin butts were collected and aged 7, 14, or 21 d, for Warner-Bratzler shear force (WBSF) analyses. Feeding zilpaterol or manipulating dietary Ca did not affect (P > 0.20) serum Ca concentrations after 2 d of realimentation. Zilpaterol increased WBSF (P < 0.05) for strip steaks aged 7 d (6.7 vs 8.5 kg) 14 d, (5.3 vs 6.9 kg) and 21 d, (5.1 vs 6.4 kg). Zilpaterol did not affect (P > 0.10) sirloin steak WBSF. Dietary Ca manipulations did not affect (P > 0.20) WBSF of strip steaks, but increased WBSF for sirloin steaks aged 7 d (7.26 vs 7.96, P < 0.05). In Exp. 2, steers (n = 12, BW = 585 ± 64 kg) were allocated to 1 of 3 dietary treatments: a typical finishing diet Control with adequate Ca (CON); a comparable diet with calcium carbonate removed from the xii supplement (Ca ±); and a diet the same as the Ca ± treatment plus 6.87 g/T zilpaterol (ZIL-Ca). Steers were fed test diets for 20 d and blood samples were acquired 1 h before feeding the CON diet to all steers. Blood samples were acquired again at 13, 17 and 21 h after realimentation to evaluate the effects of time and treatment on serum Ca. Treatments caused a difference in serum Ca over time (P < 0.05), with Ca manipulated treatments starting with lower serum Ca levels at -1 h, increasing to higher concentrations at 17 h, and decreasing to a common end point at 21 h after realimentation. Manipulating Ca metabolism is possible, but will not influence WBSF after a 3 d realimentation period.

Library of Congress Subject Headings

Beef cattle--Feeding and feeds
Calcium--Physiological effect
Adrenergic beta agonists -- Physiological effect Adrenergic beta agonists in animal nutrition
Feed additives


Includes bibliographical references (pages 33-34)



Number of Pages



South Dakota State University



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