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ANIMAL PRODUCTS |
Department of Animal Sciences, University of Arizona, Tucson 85721
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Abstract |
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 Top Abstract INTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONLITERATURE CITED |
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Key Words: Waguli • Brahman • calpain • calpastatin • carcass characteristic • tenderness
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INTRODUCTION |
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TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONLITERATURE CITED |
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; Huffman et al., 1990). Therefore, various breeding schemes have been tested in which Brahman are crossed with European breeds in an effort to obtain an animal with high heat tolerance but having the performance and meat quality attributes of the European breeds. The Santa Gertrudis was a product of early attempts in this area. To obtain a breed of cattle that possesses superior meat quality but that has the heat tolerance to perform well in feedlot conditions in the southwestern United States, the Waguli breed was developed at the University of Arizona V-V ranch near Campe Verde, Arizona. This breed results from crossing the Japanese Wagyu (Bos taurus) with the South African Tuli (Bos indicus).
The Wagyu breed is a moderately framed animal known for its ability to deposit intramuscular fat (marbling), and whose LM has low shear force values and carcasses that typically grade Choice or better and are highly palatable (Yamazaki, 1981; Lunt et al., 1993; Kuber et al., 2004; Wheeler et al., 2004). The Tuli is an African Sanga breed produced from crosses between Zebu and B. taurus animals thousands of years ago in Africa. Tuli have high fertility and maternal performance (Oliver, 1983; Schoemasn, 1989) and are similar to the Brahman in their tolerance to heat, early maturing traits, parasite resistance, and foraging ability (Holloway et al., 2002). The purpose of this study was to compare the carcass and some quality traits of the newly developed Waguli breed with those of the Brahman breed.
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MATERIALS AND METHODS |
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TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONLITERATURE CITED |
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Design, Feeding, and Sample Collection
Twelve Waguli steers were born and raised until weaning at the University of Arizona V-V ranch, near Campe Verde, Arizona, and 12 purebred Brahman steers were obtained from the Red Rock feedlot in Arizona. The 24 steers were received at the University of Arizona feedlot unit in Tucson, where the study was conducted. After the steers were acclimated to the high-concentrate diet for 14 d, the study began. The steers were weighed and this BW served as the beginning weight of the trial. At the same time, the steers were all implanted with 36 mg of zeranol (Ralgro, Schering-Plough Animal Health Corp., Summit, NJ).
The 2 breeds of steers were divided into 2 groups of 6 steers each; the 6 steers in each group were then randomly allocated into 1 of 2 diets. Diet 1 was an 86% concentrate diet, and diet 2 was a 94% concentrate diet. The diets used in this study (Table 1) were formulated according to the NRC recommendations (1996). Each steer was housed in individual pens and was fed once daily at 0600 h. Animals were weighed every 28 d, and BW were recorded. During weighing, a blood sample was taken via jugular venipuncture and placed in 10-mL Corvac tubes (Sherwood Medical Co., St. Louis, MO) for determination of serum urea nitrogen.
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Within 45 min after exsanguination, 2 samples, 2 g each, were removed from the LM at the 12th rib, were vacuum-packaged, and were stored at –140°C (Revco Ultima II Ultra-Low Freezer, Asheville, NC) until analysis for calpain and calpastatin activity. At 1 wk after slaughter, 3 steaks, each 2.54 cm in thickness, were removed from the LM of each carcass and were assigned randomly to one of the following aging periods: 7, 10, or 14 d. The 7-d steaks were immediately processed for Warner-Bratzler shear force (WBSF) values, and the 10-and 14-d steaks were vacuum-packaged and stored at 2°C for 3 or 7 d, respectively, before processing for WBSF measurements.
Determination of Carcass Characteristics
Carcass characteristics, including HCW, LM area, KPH, and adjusted fat thickness (AFT) at the 12th rib, were recorded at 48 h after slaughter. Yield grade (YG) was calculated based on the formula 2.5 + (2.5 x AFT) + (0.2 x %KPH) + (0.0038 x HCW) – (0.32 x LM). Marbling score, lean maturity, and skeletal maturity were evaluated after 48 h at 2°C (USDA, 1997). Marbling score was based on the following scale: Traces, 300 to 399; Slight, 400 to 499; Small, 500 to 599; Modest, 600 to 699; and so on. Quality grades were scored as follows: Select grade, 400 to 499; Choice grade, 500 to 599; and Prime grade, 600 to 699.
Determination of WBSF
At the end of the assigned aging period, the steaks were cooked in groups of 3 on an electric grill (George Foreman grilling machine, model GR35TMR, Lake Forest, IL) to an internal temperature of 71°C (American Meat Science Association, 1995). A Type K thermocouple (Taylor model 9800, Omega Engineering Inc., Stamford, CT) was placed in the center of each steak, and the internal temperature was monitored during cooking by using a microprocessor thermometer (model HH21, Omega Engineering Inc.).
After cooking, the steaks were allowed to cool to room temperature, and up to 10 cores (1.27-cm diameter) were removed from each steak parallel to the muscle fiber (Gruber et al., 2006). Each core was sheared perpendicular to the muscle fiber, with a WBSF machine (Model S44TJ, Emerson Electric Inc., St. Louis, MO) fitted with a dynamometer scale (Chatillon, New York, NY). Peak shear force measurements were recorded and averaged to obtain a single shear force value for each steak.
Determination of Calpain and Calpastatin Activity
Two grams of frozen LM were homogenized in 15 mL of homogenizing buffer (20-mM Tris hydrochloride, pH 7.5; 5-mM ethylene diamine tetraacetic acid; 10-mM mercaptoethanol; 1-mM Pefabloc; and 2.5-µM E-64) by using a Polytron homogenizer (Model PT-MR 3000, Kinematica AG, Littau, Switzerland). The settings were 28,400 rpm, with 2 bursts of 20 s, each separated by 30-s cooling periods. The homogenate was centrifuged at 14,000 x g for 20 min, the supernatant was filtered through glass wool, and 50 µL of the supernatant was saved on ice for protein determination (Bradford, 1976). Potassium chloride was added to the supernatant to bring it to a final concentration of 125 mM, and the supernatant was loaded into a 1.6 x 16-cm phenyl sepha-rose column (GE Healthcare, Piscataway, NJ). After flushing with 126 mL of buffer (125-mM potassium chloride; 20-mM Tris hydrochloride, pH 7.5; 5-mM ethylene diamine tetraacetic acid; and 10-mM mercaptoethanol), the calpain was eluted from the column with 5-mM ethylene diamine tetraacetic acid containing 10-mM mercaptoethanol.
All tubes containing the fractions eluted from the phenyl sepharose column were assayed for calpain activity by using the dipyrromethene boron difluoride fluorescent assay (Thompson et al., 2000) and for calpastatin activity by using the fluorescein isothiocyanate-labeled casein assay (Wolfe et al., 1989; Edmunds et al., 1991). Tubes containing calpain or calpastatin activity were pooled, and the pooled samples were concentrated by using an Amicon Ultra-15 instrument (Millipore, Billerica, MA). The amount of protein in each fraction was determined by using the Coomassie Brilliant Blue assay (Pierce, Rockford, IL). The pooled concentrated samples were assayed for calpain and calpastatin activity by using the dipyrromethene boron difluoride fluorescent assay and the fluorescein isothiocyanate-labeled casein assay, as described before.
Statistical Analysis
Data were statistically analyzed by using SAS (SAS Inst. Inc., Cary, NC). The analysis was performed by using 2 x 2 factorial design (2 diets x 2 breeds) for the 3 slaughter groups. The statistical model included the effects of breed and diet as the independent variables.
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RESULTS AND DISCUSSION |
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TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONLITERATURE CITED |
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Carcass Characteristics
Mean values for the different carcass traits measured in this study are presented in Table 2. There were no significant differences between the Waguli and Brahman breeds in HCW and in KPH. Waguli steers, however, had a larger LM area at the 12th-rib section, had greater AFT measured at the 12th-rib section, had a significantly greater marbling score, and had a greater quality grade than the Brahman steers. Surprisingly, there was no significant difference between the 2 breeds in YG, even though the Waguli steers had significantly greater AFT.
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; Franke, 1997; Casas and Cundiff, 2003), whereas another group reported that Brahman cross-bred steers had numerically greater YG than Tuli cross-bred steers (Chase et al., 2001). When compared with cattle of Angus ancestry, 2 studies (Huffman et al., 1990; Paschal et al., 1995) found that Brahman crossbred steers had greater YG than Angus crossbred steers, whereas 1 study found that Brahman-sired steers had a numerically greater YG than Angus steers even though they had less backfat than the Angus steers (Young et al., 1978). A third study found that Brahman and Angus crossbred steers had similar YG (Koch et al., 1982), similar to that reported in the present study comparing the new Waguli breed with the Brahman. Studies comparing steers having Wagyu or Tuli ancestry with steers having Angus ancestry have found that Angus and Wagyu-crossed steers had similar YG (Myers et al., 1999) or that Angus calves had lower (3.1) YG than Wagyu (3.6) calves (Wertz et al., 2002).
In the present study, Waguli steers had significantly larger LM areas than Brahman steers, even though their carcass weights were similar to the Brahman carcass weights (numerically even slightly smaller; Table 2
). This difference is likely due in part to the effect of Brahman ancestry on LM. Several studies have found that as percentage of Brahman ancestry increases, the LM area decreases (Peacock et al., 1979; Huffman et al., 1990; Pringle et al., 1997), and that Brahman and Brahman crosses produce carcasses having smaller LM areas than carcasses from British breeds or British-breed crosses (Luckett et al., 1975; Crockett et al., 1979; Peacock et al., 1982; Lopes 1986). Studies comparing LM of Wagyu and Wagyu crossbred steers with the LM of British breeds have produced differing results. Some studies have found that Wagyu crossbred bulls and heifers had larger LM than Angus crossbred bulls and heifers (Myers et al., 1999; Wertz et al., 2002), whereas other studies have found that the LM in carcasses from Angus-sired and Hereford-sired steers were similar to those in carcasses from Wagyu-sired steers (Pringle et al., 1997; Wheeler et al., 2004). Consequently, the larger LM in the Waguli steers was likely due to the Wagyu influence and not the Tuli inheritance; in addition, several studies have found no difference in LM between Brahman and Tuli steers (Herring et al., 1996; Cundiff et al., 1998).
It is generally acknowledged that animals with Wagyu ancestry fatten more rapidly and have greater marbling scores than other breeds of cattle, and that this difference in rate of fattening is reflected in the greater AFT, greater marbling scores, and greater quality grades of the Waguli animals in this study (Table 2). Quality grade is highly related to marbling; thus, Brahman steers have lower quality grades than British breeds of cattle (Butler et al., 1956; Carpenter, et al., 1961; Cole et al., 1963; Young et al., 1978; Crockett et al., 1979; Peacock et al., 1979; Adams et al., 1982; Koch et al., 1982; Crouse et al., 1989; Huffman et al., 1990; Whipple et al., 1990; Cundiff et al., 1993; Casas and Cundiff, 2003). Marbling scores have been reported to decrease with increasing Brahman inheritance (Pringle et al., 1997), and this lower marbling score has been associated with the decreased tenderness of Brahman cattle (Johnson et al., 1990b). Even Tuli-sired steers were reported to have greater marbling scores than Brahman-sired steers (Herring et al., 1996; Franke, 1997; Cundiff et al., 1998). Steers from Wagyu crosses had greater marbling scores than steers from Angus crosses (Lunt et al., 1993; Myers et al., 1999; Wertz et al., 2002) or from Wagyu x Limousin crossbred steers (Kuber et al., 2004); the former result is consistent with the widely noted marbling ability of the Wagyu breed when compared with the Angus breed (Yamzaki, 1981; May 1993; Mir et al., 1999). Wagyu-sired steers also had a greater percentage of fat content in their LM than Hereford-sired steers (Pitchford et al., 2002).
The Angus breed has a reputation for having a high degree of marbling among the British breeds, but a comparison of Wagyu heifers with Angus heifers showed that 60% more Wagyu heifers than Angus heifers were graded Choice (Wertz et al., 2002). Likewise, 19% more Wagyu cross carcasses graded Choice or better and 82% more of the Wagyu carcasses graded Choice than Angus crosses (Myers et al., 1999). Comparing Wagyu-sired, Hereford-sired, and Angus-sired steers, Wheeler et al. (2004) found that the Wagyu-sired steers had the greatest percentage of Choice, YG 1 or 2. These studies indicate that the Wagyu breed has consistently greater marbling and quality scores than even the Angus breed, and that the Wagyu may therefore be an excellent choice for crossing with a B. indicus species to increase quality of the cross.
Although animals having Wagyu ancestry generally have greater marbling scores and greater backfat thickness than other breeds, there was no difference between the Waguli and Brahman steers in amount of KPH fat in the present study (Table 2). Earlier studies generally found no effect of breed on amount of KPH when Brahman x Angus, Senepol x Angus, and Tuli x Angus were compared (Chase et al., 2001) or when Brahman and Angus steers were compared (Huffman et al., 1990), although one study found that Angus steers had slightly less (0.2%) KPH than Wagyu steers (Myers et al., 1999). It seems that animals with Wagyu ancestry deposit fat differently than animals having British or Brahman ancestry, with proportionately more fat being deposited intramuscularly and subcutaneously and less fat being deposited around interior organs.
Calpain and Calpastatin Activity and Shear Force Values
The calpain-calpastatin system has an important role in postmortem tenderization of meat (Koohmaraie et al., 1988; Dransfield, 1992; Koohmaraie, 1992), so the muscle samples taken in this study were assayed for calpain and calpastatin activity. No attempt was made to separate µ-calpain from m-calpain, and the assay measures combined µ- and m-calpain activity. The cal-pain and calpastatin assays varied considerably from animal to animal for both the Waguli and the Brahman animals. As a result of this variation, there were no significant differences in calpain activity between breed and between high-energy and low-energy diets (Table 3). Calpain activity was slightly greater in Waguli LM than in Brahman LM, but this difference was not significant (P = 0.57). In addition, the greater calpain activity of the animals on the high-energy diet was not significant (P = 0.68). Calpastatin activity was much greater in Brahman LM than in Waguli LM (Table 3), and despite the animal-to-animal variation, this difference was significantly different at P = 0.002. Diet had no effect on calpastatin activity, (Table 3; P = 0.38). It should be pointed out that these calpain and calpastatin activities are all 0-time (at-death) activities.
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). Previous studies have shown that muscle from animals having Brahman ancestry age more slowly than muscle from British breed animals (Johnson et al., 1990b; Whipple et al., 1990; O’Connor et al., 1997) and that steaks from Brahman animals should be aged for approximately 21 d to compensate for the delayed aging process in these animals (O’Connor et al., 1997). The energy content of the diets had no effect on LM tenderness of either Waguli or Brahman (Table 4). The increase in toughness between 7 and 10 d of postmortem aging is unusual (Table 4), and it is unclear why this occurred. That shear force values for both the Waguli and the Brahman increased between 7 and 10 of aging suggests that it may be related to how the samples were handled, but to the best of our ability, the samples were all processed identically.
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; Whipple et al., 1990; Johnson et al., 1990a; Shackelford et al., 1991; Cundiff, 1993; Pringle et al., 1997). Because we did not include any British breeds in this study, it is not known whether calpastatin activity in Waguli muscle was lower, greater, or the same as calpastatin activity in muscles from the British breeds, although the absolute values and the relative differences with calpastatin activity in the Brahman suggest that calpastatin activities in the Waguli are similar to those in the British breeds. The high calpastatin activities and high shear force values of Brahman muscle are also consistent with earlier studies that compared muscle from B. taurus with B. indicus (Brahman) breeds and that suggested that high calpastatin activity is the cause of the low tenderness and long aging times required for Brahman muscle (Wheeler et al., 1990; Whipple et al., 1990; Shackelford et al., 1991; Cundiff, 1993; Morgan et al., 1993; O’Connor et al., 1997). In conclusion, the newly developed Waguli breed was created in the hope that it would retain the heat tolerance traits of the B. indicus, but that it would not have the decreased meat quality traits (marbling and WBSF) that have been associated with the B. indicus species. The results indicate that, when compared with Brahman steers, Waguli steers have more marbling (hence would grade greater), have improved WBSF, and age more rapidly during postmortem storage. Moreover, the increased tenderness and rapid aging of Waguli is associated with a reduced calpastatin content in the Waguli LM. Hence, the Waguli would seem to be a highly desirable breed for use in hot climates.
The present study indicates the usefulness of the newly developed breed Waguli. It tolerates the heat, because it was raised in Tucson, Arizona (the Southwest in the United States). This study indicates Waguli steers possess acceptable marbling ability, quality grades, yield, and WBSF.
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Footnotes |
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2 Corresponding author: jam{at}ag.arizona.edu
Received for publication September 27, 2007. Accepted for publication February 20, 2008.
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LITERATURE CITED |
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TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONLITERATURE CITED |
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| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
