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ANIMAL PRODUCTS |
Department of Animal Sciences, University of Kentucky, Lexington 40546
Abstract
Previous studies have shown that supplementation of vitamin D3 to cow diets for 4 to 10 d before slaughter lowers Warner-Bratzler shear force (WBSF) values and increases sensory tenderness scores in beef cuts. The present study was conducted to evaluate the effects of vitamin D3 supplementation on muscle calcium concentration, WBSF values, and sensory tenderness ratings of LM and semitendinosus (ST) muscles from cull, predominately Angus, cows (eight cows per treatment). Treatments included 0 (control), 5 million IU, or 7.5 million IU of vitamin D3 supplemented daily for 7 d preslaughter. Twenty-four hours after slaughter, 2.54-cm-thick LM and ST muscle steaks were cut; aged for either 0, 7, 14, or 21 d (ST steaks aged for 7 d only); and frozen at -20°C for WBFS and sensory analysis. Mean values for LM calcium concentration tended to increase (P = 0.14) with vitamin D3 supplementation (154, 176, and 183 µig/g, fresh basis, for 0, 5, and 7.5 million IU/d, respectively). After 7 d of aging, LM steaks from cows fed 7.5 million IU had lower (P < 0.05) WBSF values than 7-d steaks from controls and cows fed 5.0 million IU/d aged 7 d; however, vitamin D3 supplementation had no (P > 0.05) effect on WBSF values of ST steaks aged 7 d. Vitamin D3 supplementation did not (P > 0.05) affect sensory tenderness ratings for either LM or ST steaks at any aging period. Aging, however, had a linear (P < 0.001) effect on tenderness, with an increase in tenderness as aging time increased from 0 to21 d. Thus, results from the present study indicate that vitamin D3 supplementation, at these levels and duration before slaughter, provided little benefit to muscle tenderness of beef from cull cows.
Key Words: Beef • Calcium • Tenderness • Vitamin D
Introduction
Cull cows are normally older in age and produce carcasses that have USDA quality grades of Commercial, Utility, Cutter, and Canner. These carcasses are typically used for manufacturing beef because physiological maturity of the carcass and tenderness are inversely related (Boleman et al., 1996
). Because meat palatability is decreased, marketing options for this industry segment are limited. If tenderness was improved, marketing flexibility of the more valuable primal/subprimal cuts (such as the rib and loin) from these carcasses could be increased (Boleman et al., 1996).
Ante- and postmortem methods of increasing muscle tenderness through enzymatic activity have been developed. The postmortem infusion of muscle with calcium chloride has been shown to increase calcium availability to the proteases responsible for muscle tenderness (Koohmaraie and Shackelford, 1991). Vitamin D3 supplementation of cattle prior to slaughter increased meat tenderness (Swanek et al., 1999; Karges et al., 1999; Montgomery et al., 2000). However, Scanga et al. (2001) reported that vitamin D and calcium supplementation from 1 to 5 x 106 IU for 2 to 8 d before slaughter increased serum calcium concentration, but did not improve cooked longissimus muscle tenderness. Therefore, the present study was designed to investigate the effects of varying levels of dietary vitamin D supplementation on the palatability of longissimus and semitendinosus muscles from cull beef cows.
Materials and Methods
Twenty-four cull Angus-crossbred cows (approximately 78 mo of age and weighing from 463 to 556 kg) were allotted randomly to one of three high-concentrate finishing diets supplemented with vitamin D3 (eight cows/treatment): 1) finishing diet devoid of supplemental vitamin D3 (control); 2) finishing diet supplemented with 5.0 x 106 IU of vitamin D3•cow-1•d-1; and 3) finishing diet supplemented with 7.5 x 106 of IU vitamin D3•cow-1•d-1. The finishing diet consisted of 90.0% ground corn and cob and 10% supplement (3.55% urea, 76.12% soybean meal, 2.50% salt, 4.55% dicalcium phosphorus, 10% calcium carbonate, 0.69% vitamin A, 0.19% Rumensin [Elanco Animal Health, Greenfield, IN], 0.22% trace minerals, 1.12% Dynamate [International Minerals Corp., Chicago, IL], and 1.0% selenium). Finishing diets were formulated by a commercial feed company to targeted levels of Vitamin D3. Cows were individually fed the finishing diet for 3 wk before the start of the vitamin D3 supplementation, which began in the fourth wk of the finishing period and was fed for 7 d before slaughter. Cows had ad libitum access to their respective diets and water.
After the fourth wk of receiving the finishing diet, cows were shipped approximately 30 km to a commercial meat processor in Cincinnati, OH, and humanely slaughtered according to industry-accepted procedures. Carcasses were conventionally air-chilled at 3°C for 24 h, and yield and quality grade factors (USDA, 1986) were measured by trained personnel from the University of Kentucky.
Following carcass data collection, carcasses were fabricated into primal and subprimal cuts according to Institutional Meat Purchase Specifications (IMPS; USDA, 1986). Boneless strip loins (IMPS #180), as well as eye of the rounds (semitendinosus muscle; IMPS #171c), were captured during fabrication, vacuum-packaged, and transported to the University of Kentucky Meat Laboratory at <4°C. Strip loins were fabricated into 2.54-cm-thick steaks for sensory evaluation, Warner-Bratzler Shear Force (WBSF) determination, total muscle calcium (Ca) concentration, and collagen content. Semitendinosus muscles were fabricated into 2.54-cm-thick steaks for sensory evaluation and WBSF. Steaks allocated for WBFS and sensory panel were vacuum-packaged at 22 mm Hg in a model AG 900 Koch Multivac vacuum-packager (Kansas City, MO) in double, air-impermeable Cryovac bags (Cryovac North America, W.R. Grace and Co., Duncan, SC), and aged for either 0, 7, 14, or 21 d at 4°C. After completion of the appropriate aging period, steaks were frozen, and stored at -29°C until analysis. Steaks for total muscle Ca concentration and collagen analysis were vacuum-packaged as described previously, frozen, and stored at -29°C until analysis could be performed.
Muscle Calcium
Vacuum-packaged steaks were shipped on dry ice to Instrumentation Laboratory (Franklin, MA) for measurement of total muscle Ca by atomic absorption spectrophotometry following the modified wet-ashing procedure of Du et al. (1996). Thawed, 2.5-g ground steak samples were dried in a drying oven set at 100°C for 24 h and weighed. Concentrated nitric acid (12 mL) were added to samples, which were then digested on a 80°C steam plate for 24 to 36 h. The nitric acid was evaporated off, and 8 mL of 30% hydrogen peroxide was added to each sample. Samples continued to digest for 24 h on a steam plate. After hydrogen peroxide was evaporated, 10 mL of 1 N hydrochloric acid was added to each flask to reconstitute minerals, and samples were diluted in a 1:20 ratio with deionized water. Upon completion of the digestion process, the amount of Ca was measured with an atomic absorption spectrophotometer using the wavelength 422.7 nm.
Warner-Bratzler Shear Force Determination
Steaks were thawed at 5°C for 24 h, and internal temperature was recorded prior to cooking. Steaks were broiled on a Farberware Open Hearth Electric broiler (Kidde, Inc., Bronx, NY) to an internal temperature of 40°C, turned, and cooked to a final internal temperature of 71°C. Internal temperature was monitored with a digital thermocouple (Atkins Digital Thermometer model 31308-KF, Gainesville, FL). Samples were chilled for approximately 4 h to room temperature prior to removal of six 1.27-cm-diameter cores parallel to the longitudinal orientation of the muscle fibers. Cores were then sheared once in the center by an Instron Universal Testing Machine (model 4301, Instron Corp., Canton, MA) with a WBSF attachment at a crosshead speed at 20 cm/min. Values for the six cores per steak were averaged for statistical analysis.
Sensory Evaluation
Palatability characteristics of LM steaks aged 0, 7, 14, and 21 d, and semitendinosus (ST) steaks aged 7 d, were evaluated by an eight-member panel trained according to AMSA (1995) guidelines. All ST steaks were evaluated at the same time and LM steaks from each aging period were randomly evaluated by panels. Steaks were prepared as described for WBSF determinations, cut into 1-cm cubes, and served warm in a randomized order to sensory panelists. Each panelist individually evaluated two cubes from each sample steak for juiciness, beef flavor intensity, tenderness, and connective tissue amount using 8-point scales (8 = extremely juicy, intense, tender, and none to 1 = extremely dry, bland, tough, and abundant) and for off-flavor on a 4-point scale (1= intense to 4 = none). Apple juice was served between samples to eliminate flavors from previous samples. To mask visual differences between samples, red lights illuminated sensory booths (AMSA, 1995).
Muscle Collagen Content
Steak samples for muscle collagen content were ground, frozen, and sent to Woodson-Tenent Laboratories, Inc. (Memphis, TN) to be analyzed for hydroxyproline content following AOAC (1995) guidelines. Samples were hydrolyzed in 30 mL of sulfuric acid and dried for 16 h in a drying oven set at 105°C. Samples were filtered and diluted with deionized water so that the hydroxyproline concentration of the final dilution was in the range of 0.5 to 2.4 µg/mL. Chloramine-T was added to the samples to oxidize hydroxyproline, and samples were allowed to stand for 20 min at room temperature. Color reagent (1 mL of 4-dimethylaminodenzaldehyde) was added to each sample, and samples were capped and placed in a 60°C water bath for 15 min. After the samples cooled, the absorbance of the solutions was measured in glass cells at a wavelength of 558 nm with a spectrophotometer (Shimadzu model UV160U, Columbia, MA). Hydroxyproline content (g/100 g of muscle) was calculated using the equation (h x 2.5) ÷ (m x V); where h = hydroxyproline (g/2 mL of filtrate), m = sample weight (g), and V = volume (mL) of filtrate taken for dilution to 100 mL for hydrolysis.
Statistical Analyses
Data were analyzed as a completely randomized design using the General Linear Models procedure of SAS (SAS Inst. Inc., Cary, NC) with treatments arranged in a 3 x 4 factorial arrangement with three levels of vitamin D3 (0, 5.0, and 7.5 x 10 IU/d) and four aging periods (0, 7, 14, and 21 d). Least squares means were separated by the LSD (P < 0.05) procedure, and orthogonal polynomial contrasts were used to determine linear, quadratic, or cubic response trends due to aging.
Results and Discussion
Total Muscle Calcium Concentration
Although vitamin D3 supplementation did not statistically increase muscle Ca concentrations, muscle Ca levels tended to increase (P = 0.14) numerically with increasing dietary vitamin D3 (Table 1). These results supported previous findings by Swanek et al. (1999) that dietary vitamin D3 supplementation (5.0 x 106 IU daily for 7 d and 7.5 x 106 daily for 10 d) increased the muscle Ca concentration in steers by 6 and 7.1 g/g, respectively.
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. There was dietary vitamin D3 x aging period interaction (P < 0.05), where vitamin D3 treatment had no effect on WBSF values of unaged (0-d) steaks; however, after 7 d of aging, LM steaks from cows fed 7.5 x 106 IU/d vitamin D3 had lower shear force values than steaks from cows fed 0 and 5.0 x 106 IU/d vitamin D3. After aging for 14 and 21 d, LM steaks from cows fed the diet supplemented with 5.0 x 106 IU/d vitamin D3 had greater (P < 0.05) WBSF values than steaks from cows fed the control diet, whereas LM steaks from cows supplemented with 7.5 x 106 IU/d vitamin D3 were not (P > 0.05) different from those of control-fed cows.
Swanek et al. (1999) found similar results after 7 d of aging in LM steaks from vitamin D3-supplemented (5.0 x 106 IU/d for 7 d) steers, demonstrating lowered shear force values compared to controls. Likewise, extending the postmortem aging time to either 14 or 21 d negated any advantage associated with vitamin D3 supplementation (Swanek et al., 1999). However, when 7.5 x 106 IU of vitamin D3 was fed for 10 d, there was a significant difference in shear force values between 14-d-aged steaks from cattle supplemented vitamin D3 and control diets (Swanek et al., 1999). Karges et al. (1999) presented results indicating decreased shear force values for LM and gluteus medius steaks from steers supplemented with 6 x 106 IU/d vitamin D3 for 4 or 6 d when compared to control steers. Furthermore, Montgomery et al. (2000) reported the use of 5 x 106 and 7.5 x 106 IU of supplemental dietary vitamin D3, given daily for 9 d before slaughter, reduced WBFS values of strip steaks aged 14 d. In contrast, Scanga et al. (2001) indicated that oral supplementation of vitamin D3 at doses of 1 and 5 x 106 IU for 2 to 8 d before slaughter failed to improve the WBFS values of steaks aged for 2, 7, 14, or 21 d.
Semitendinosus Steaks.
There was no (P > 0.05) vitamin D3 supplementation level x aging period interaction for WBSF values of ST steaks. Moreover, neither the main effects of vitamin D3 level nor postmortem aging period were effective (P > 0.05) in lowering shear force values in ST steaks (Table 2). Uncharacteristically, aging had a quadratic effect (P < 0.05) on mean WBFS force values (5.63, 6.46, and 5.64 kg for steaks aged 2, 14, and 21 d, respectively), which followed the same trend observed in LM steaks.
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demonstrated that feeding 6 x 106 IU/d vitamin D3 for 6 d prior to slaughter tended to reduce shear force values of biceps femoris steaks compared to steaks from control steers. Furthermore, Montgomery et al. (2000) observed that supplemental vitamin D3, give daily for 9 d before slaughter, did lower WBSF values of semimembranosus steaks aged 14 d. Even though Eilers et al. (1996) observed a quadratic relationship between shear force and aging time in semimembranosus steaks of steers and heifers, they noted a sharp reduction in shear force values between 6 and 12 d postmortem, followed by a very gradual decline in shear force values from 12 to 24 d postmortem.
Sensory Panel Evaluation
Longissimus Muscle Steaks.
The effects of dietary vitamin D3 treatment on sensory panel evaluations over the different postmortem aging periods are exhibited in Table 1. When sensory data were analyzed across aging periods, vitamin D3 supplementation had no (P > 0.05) effects on sensory panel-evaluated juiciness, beef-flavor intensity, tenderness, detectable connective tissue, and off-flavor. Likewise, there was no (P > 0.05) vitamin D3 supplementation level x aging period interaction for any traits; thus, data were averaged across times and main effect means were reported for treatments.
There was a cubic (P < 0.01) effect of postmortem aging period on sensory panel juiciness ratings (Table 2). Moreover, there was a linear (P < 0.001) relationship of aging time on beef-flavor intensity, with an increase in mean beef flavor intensity ratings over time. As expected, tenderness scores increased linearly (P < 0.001) as aging time increased from 0 to 21 d. Additionally, sensory panel detected connective tissue scores decreased linearly (P < 0.01) with increase aging. At 2 d postmortem, there were no (P > 0.05) differences in steaks from control vs. vitamin D3-supplemented animals for any of the evaluated categories (data not shown). When steaks aged for 7 d postmortem were evaluated, no (P > 0.05) differences were found in juiciness, beef flavor intensity, and off-flavor between vitamin D3-supplemented and control cows. Tenderness ratings tended to be lower (P = 0.12) in 7-d-aged steaks from vitamin D3 than control cows, which was likely a response to the increase (P < 0.10) in the amount of detected connective tissue in the vitamin D3 steaks (data not shown).
No (P > 0.05) differences were detected in juiciness, connective tissue, and off-flavor ratings of steaks from control and vitamin D3 cows aged for 14 d postmortem. Cows fed 5.0 x 106 IU vitamin D3/d had lower (P < 0.05) beef flavor intensity scores than the controls and cows fed 7.5 x 106 IU vitamin D3/d (data not shown). Although tenderness ratings were not (P > 0.05) detected between the controls and the vitamin D3-supplemented cows, steaks from cows fed 7.5 x 106 IU vitamin D3/d received higher (P < 0.05) tenderness scores than steaks from cows fed 5.0 x 106 IU/d (data not shown). Furthermore, steaks from cows fed 7.5 x 106 IU/d of vitamin D3 had higher (P < 0.05) off-flavor ratings than steaks from cows fed 5.0 x 106 IU/d of vitamin D3 (data not shown). At 21 d postmortem, no (P > 0.05) differences were detected among treatments for any of the evaluated categories.
In agreement with results from the present study, Montgomery et al. (2000) demonstrated that supplemental vitamin D3 did not enhance tenderness, juiciness, flavor, or overall palatability scores of strip loin steaks. In contrast, Swanek et al. (1999) reported vitamin D3 supplementation improved trained sensory tenderness ratings. Furthermore, no differences were detected in sensory scores for juiciness, connective tissue amount, beef flavor intensity, or off-flavor between steaks from vitamin D3-supplemented and control steers (Swanek et al., 1999).
It has been well documented that postmortem aging improves sensory panel tenderness scores. Eilers et al. (1996) reported that panel tenderness scores for LM steaks increased quadratically as length of the aging period increased from 6 to 24 d. Diles et al. (1994) also observed increased sensory panel ratings for tenderness, as well as flavor intensity, flavor desirability, and overall palatability, in loin steaks from mature cows aged 14 d. Furthermore, Morgan et al. (1993) documented that aging for 7 and 14 d increased subjective scores for overall tenderness in the LM from mature bulls.
Semitendinosus Steaks.
Steaks from vitamin D3-supplemented cows received higher (P < 0.05) sensory panel ratings for off-flavors than steaks from cows fed the control diet (Table 2). Steaks from cows supplemented with 5.0 x 106 IU/d vitamin D3 received higher (P < 0.05) off-flavor scores than steaks from cows fed the control diet, whereas steaks from cows supplemented with 7.5 x 106 IU/d vitamin D3 tended to be rated higher (P = 0.10) for off-flavors that steaks from control. There were no (P > 0.05) differences between control steaks and steaks from either vitamin D3 supplementation level for any other sensory categories.
Again, results from the present study contradict those of Swanek et al. (1999), who observed improved sensory panel tenderness scores in steaks from vitamin D3-supplemented steers compared to steaks from control. On the other hand, Montgomery et al. (2000) reported that elevating the dietary vitamin D3 level did not affect sensory evaluation tenderness scores.
Muscle Collagen Content
Collagen content in the LM and ST was not (P > 0.05) different among either vitamin D3 treatments or aging periods (Table 1). Because muscle collagen amounts were virtually identical between vitamin D3 treatments, observed differences in subjective and objective measures of tenderness in LM steaks were likely responses to differing rates and extents of postmortem tenderization of the myofibrillar component of tenderness in beef from cull cows.
Overall, the supplementation of vitamin D3 at either the 5.0 or 7.5 x 106 IU/d level for 7 d prior to slaughter had only minimal effects on tenderness of the LM steaks, even though vitamin D3 was effective in increasing muscle calcium concentrations. Because hydroxyproline percentages were similar across dietary vitamin D3 treatments, collagen content could not explain the ineffectiveness of vitamin D3 supplementation on cooked beef tenderness. Postmortem aging effectively increased LM tenderness, but only after 14 d of aging was there a decrease in WBSF values and increased sensory panel tenderness ratings.
Implications
These results indicate that supplementing Angus crossbred cull beef cows with vitamin D3 had little effect in increasing tenderness in the longissimus and semitendinosus muscle. Postmortem aging increased longissimus muscle tenderness and may increase the value and acceptability of the middle meats from cull beef cows. Evidence from the present study suggests that the longissimus muscle of cull cows should be aged for a minimum of 14 d postmortem; however, aging did not alter semitendinosus muscle tenderness, regardless of duration of the aging period. Consequently, this muscle and the related muscles of the round should be used for further-processed meat products, such as ground beef or restructured steaks.
Footnotes
1 Present address: Cooperative Extension Service, University of Georgia, Athens 30602. 
3 Present address: Department of Animal Sciences, Texas A&M University, College Station 77843.
2 Correspondence: 205 W.P. Garrigus Bldg. (phone:859-257-7550; fax: 859-257-5318; e-mail: wmikel{at}uky.edu).
Received for publication November 21, 2001. Accepted for publication June 30, 2003.
Literature Cited
AMSA. 1995. Research guidelines for cookery, sensory evaluation, and tenderness measurements of fresh meat. Am. Meat Sci. Assoc., Chicago, IL.
AOAC. 1995. Official Methods of Analysis. (16th ed.) Assoc. Offic. Anal. Chem., Arlington, VA.
Boleman, S. J., R. K. Miller, M. J. Buyck, H. R. Cross, and J. W. Savell. 1996. Influence of realimentation of mature cows on maturity, color, collagen solubility, and sensory characteristics. J. Anim. Sci. 74:2187–2194.[Abstract]
Diles, J. J. B., M. F. Miller, and B. L. Owen. 1994. Calcium chloride concentration, injection time, and aging period effects on tenderness, sensory, and retail color attributes of loin steaks from mature cows. J. Anim. Sci. 72:2017–2021.[Abstract]
Du, Z., R. W. Hemken, and R. J. Harmon. 1996. Copper metabolism of Holstein and Jersey cows and heifers fed diets high in cupric sulfate or copper proteinate. J. Dairy Sci. 79:1873–1880.[Abstract]
Eilers, J. D., J. D. Tatum, J. B. Morgan, and G. C. Smith. 1996. Modification of early-postmortem muscle pH and use of postmortem aging to improve beef tenderness. J. Anim. Sci. 74: 790–798.[Abstract]
Karges, K., J. B. Morgan, F. N. Owens, and D. R. Gill. 1999. Effects of feeding vitamin D3 on carcass characteristics of beef cows. Proc. Recip. Meat Conf. 52:139 (Abstr.).
Koohmaraie, M., and S. D. Shackelford. 1991. Effect of calcium chloride infusion on the tenderness of lambs fed a ß-adrenergic agonist. J. Anim. Sci. 69:2463–2471.[Abstract]
Montgomery, J. L., F. C. Parrish, Jr., D. C. Beitz, R. L. Horst, E. J. Huff-Lonergan, and A. H. Trenkle. 2000. The use of vitamin D3 to improve beef tenderness. J. Anim. Sci. 78:2615–2621.
Morgan, J. B., T. L. Wheeler, M. Koohmaraie, J. W. Savell, and J. D. Crouse. 1993. Meat tenderness and the calpain proteolytic system in longissimus muscle of young bulls and steers. J. Anim. Sci. 71:1471–1476.[Abstract]
Scanga, J. A., K. E. Belk, J. D. Tatum, and G. C. Smith. 2001. Supranutritional oral supplementation with vitamin D3 and calcium and the effects on beef tenderness. J. Anim. Sci. 79:912–918.
Swanek, S. S., J. B. Morgan, F. N. Owens, D. R. Gill, C. A. Strasia, H. G. Dolezal, and F. K. Ray. 1999. Vitamin D3 supplementation of beef steers increases longissimus tenderness. J. Anim. Sci. 77:874–881.
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