Beef tenderness and management of calf-fed Holstein steers to meet market standards
Date
2013
Authors
Howard, Scott Thomas, author
Belk, Keith E., advisor
Woerner, Dale R., committee member
Tatum, J. Daryl, committee member
Scanga, John A., committee member
Salman, M. D., committee member
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Abstract
Tenderness is one of the most influential sensory attributes determining consumer acceptance of beef products. Beef at retail represents production of a diverse cattle population, including both beef breeds and cattle bred for milk production. Objectives of this work were to first benchmark tenderness at the retail level and then determine appropriate management strategies to maximize quality and yield of calf-fed Holstein steers. Fifty-four stores in thirty U.S. cities were sampled from June 2011 through May 2012 to benchmark tenderness of beef steaks at retail as assessed by Warner-Bratzler shear force (WBSF).Top loin (N = 980) and sirloin (N = 860) steaks were purchased and shipped via overnight delivery to Colorado State University, Fort Collins, CO. The survey was divided into two periods based on samples shipped fresh and frozen on arrival (Period 1) or samples shipped frozen and stored frozen (Period 2). Mean WBSF values during Period 1 were 2.9 and 3.9 kg for top loin and sirloin steaks, respectively. Frequencies of steaks classified as tough (WBSF ≥ 4.4 kg) were 8.6% and 17.7% for top loin and sirloin steaks, respectively. Examination of coefficients of variation associated with means reflecting the influence of freezing, retail display and shipping suggested that variance remained unchanged (± 2.0%) with respect to shear force values; however, mean shear force values were reduced as a result of shipping conditions. Mean WBSF values during Period 2 were 3.4 and 4.0 kg for top loin and sirloin samples, respectively. Frequencies of steaks classified as tough were 14.3% and 24.8% for top loin and sirloin steaks, respectively. Calf-fed dairy steers comprise approximately 10% of fed-beef harvested in the United States, annually (Moore et al., 2012).This population of cattle is much different genetically and requires use of growth promotants to meet comparable feedlot performance to that of beef breeds. The effect of beta-agonist supplementation on live performance, carcass characteristics, fabrication yields and beef quality of calf-fed Holstein steers was investigated using steers implanted with a combination trenbolone acetate/estradiol based implant and blocked by initial weight into pens (N = 32). Pens consisted of 90 steers each and were randomly assigned to one of four management strategies including: implant only, ractopamine hydrochloride (RH) fed at 300 mg/hd/d for the final 30 d of finishing or RH fed at 400 mg/hd/d for the final 30 d of finishing, and zilpaterol hydrochloride fed at 6.8 g/ton for 23 d with a 3 d withdrawal prior to harvest. Feed efficiency was improved in beta-agonist fed steers 18 to 25% and hot carcass weight was increased by 1.8 to 3.7% (P < 0.05). Beta-agonists increased saleable yield by 0.6 to 1.9%, decreased fat by 0.6 to 1.3% and shifted tissue distribution such that a greater percentage of side weight was comprised of the muscles of the round (P < 0.05). Changes in development were observed as a result of beta-agonist use, specifically as an increased proportion of weight comprised of muscles of the hindquarter (P < 0.05). Use of beta-agonists negatively impacted shear force and sensory attributes. Beta-agonists had no effect on marbling; however, supplementation using any treatment increased shear force by 9 to 26%. Zilpaterol hydrochloride reduced trained panel ratings for tenderness, juiciness and flavor, but this was not observed in beef from steers treated with RH at 300 mg/hd/d. These effects were nearly linear as dose and potency of beta-agonists increased. The most aggressive beta-agonist treatments increased incidence of samples failing to be certified as tender from just over 10% in controls to approximately 20 to 25% at 21 d postmortem (P < 0.05). To produce beef comparable to current tenderness levels at retail, producers must appropriately manage use of beta-agonists and implants in populations of calf-fed Holstein steers.
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Subject
beef
tenderness
shipping
beta-agonist
Holstein
audit