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Effects of Days on Concentrate Feed and Postmortem Aging on Carcass and Palatability Characteristics of Selected Muscles from Cull Beef Cows1
The Professional Animal Scientist 24 (2008):334–341 ©2008 American Registry of Professional Animal Scientists
E fFeed fects of Days on Concentrate and Postmortem Aging on Carcass and Palatability Characteristics of Selected Muscles from Cull Beef Cows1 A. M. Stelzleni,2 D. D. Johnson, and T. A. Thrift Department of Animal Sciences, University of Florida, Gainesville 32611
ABSTRACT Twenty-four beef cows were selected to examine the effects of concentrate feeding on performance and to examine the effects of concentrate feeding and postmortem aging (10 or 20 d) on the triceps brachii lateral and long heads, infraspinatus, longissimus lumborum, psoas major, gluteus medius, tensor fascia latae, rectus femoris, and vastus lateralis. Cows were randomly assigned to a concentrate diet for 0, 42, or 84 d. Carcass characteristics were measured and Warner-Bratzler shear force, sensory evaluation, and collagen analyses were performed on selected muscles. Cow BW, ADG, and BCS increased (P < 0.02) after 84 d. Hot carcass weight, ribeye area, fat thickness, marbling, and muscling increased (P < 0.02) after 84 d. Soluble collagen content increased (P < 0.01) in the triceps brachii-long head and longissimus lumborum after 84 d. There was a days on concentrate × muscle interaction (P < 0.01) for Warner-Bratzler shear force with the 1 This research was funded in part by America’s beef producers through contributions made to the Beef Checkoff. 2 Corresponding author: [email protected]
longissimus lumborum and gluteus medius decreasing with increasing days. Sensory evaluation showed that steaks became more tender (P < 0.01) after 84 d and exhibited less (P < 0.01) off-flavor after 42 d. Extended postmortem aging (20 d) decreased (P < 0.01) WarnerBratzler shear force and increased (P < 0.01) sensory tenderness; however, postmortem aging did not increase (P > 0.05) sensory off-flavor detection. Concentrate feeding of cull cows for 84 d improved carcass characteristics and the tenderness of several muscles. These muscles may be aged for 20 d postmortem to achieve maximal tenderness without detrimental off-flavor production. Key words: concentrate feeding, cull cow, carcass characteristics, tenderness, palatability
INTRODUCTION Many of the cull cows entering the market are sold at a BCS of 4 or lower on a 9-point scale (NCBA, 1999). Increasing BCS to 6 before marketing may be advantageous to both producers and processors (Apple, 1999; Apple et al., 1999). Recent
cattle audits have identified several economical concerns for cull cow carcasses, including light muscling, low QG, light carcass weights, and yellow fat (NCA, 1994; Roeber et al., 2001). Short-term feeding is a practical management tool for achieving moderate BCS and improving carcass and quality characteristics. Shortterm feeding before slaughter has been known to decrease shear force values and increase sensory tenderness, soluble collagen content, and percent soluble collagen in the LM of cull beef cows (Miller et al., 1987). Short-term feeding after culling and before slaughter has also been shown to improve carcass and beef quality characteristics of cull cows (Brown and Johnson, 1991). However, little research has focused on the effects of realimentation on the quality of muscles other than the LM (Dryden et al., 1979). It was hypothesized that realimentation and postmortem aging would improve the quality and sensory characteristics of selected muscles from cull beef cow carcasses, thus increasing their utility beyond ground or comminuted products. Therefore, the objectives of this
Carcass attributes of concentrate-fed cull beef cows
Table 1. Least squares means of cull cow live traits before and after concentrate feeding for 0, 42, or 84 d Days on feed Item Age, yr Starting BCS1 Ending BCS1 Starting BW, kg Ending BW, kg ADG, kg/d a-c 1
0d 5.25 4.9 4.9c 491.3 491.3b 0.00b
42 d
84 d
SEM
5.50 4.7 5.4b 485.3 500.7b 0.37b
5.63 4.4 6.0a 497.8 581.1a 0.99a
0.47 0.20 0.17 20.86 22.96 0.16
Least squares means within a row with different superscripts differ (P < 0.05).
Richards et al., 1986.
research were to 1) determine the effects of realimentation on physical, chemical, and sensory characteristics of key muscles from cull beef cows; and 2) evaluate the effects of postmortem aging on various muscles from cull beef cows realimented for 0, 42 or 84 d.
MATERIALS AND METHODS The following research and protocols were reviewed and approved by the University of Florida Institutional Animal Care and Use Committee.
Animal Selection and Treatment Twenty-four beef cows were selected from the 2 University of Florida (Gainesville, FL) beef herds after being culled from the herds in late October due to failure to conceive after 2 consecutive years. Angus × Brahman cows were selected based upon the criterion that they previously had produced at least 2 calves. Cull cows selected for the experiment were weighed and assigned BCS (Richards et al., 1986) and were randomly allotted to 1 of 3 realimentation groups (n = 8 per group): 1) 0 d on concentrate feed, 2) 42 d on concentrate feed, and 3) 84 d on concentrate feed. Cow age, BCS, and BW were similar for all groups (Table 1), and all cows had been previously pastured on common Bahiagrass (Paspalum ssp.) and Ber-
mudagrass (Cynodon ssp.) throughout the summer and early fall. Cows that were fed for 42 and 84 d received pour-on anthelmintic (Eprinex-Ivomec, Merial, Iselin, New Jersey) at a rate of 10 mL/100 kg of BW, and were placed in a semidrylot environment allowing 0.06 ha per cow at the University of Florida Beef Teaching Unit (Gainesville, FL). All cows were fed as one group from bunks that allowed 1.0 m/cow of bunk space. Ad libitum access to water and shade canopy was provided at all times. Cows (42 and 84 d groups) were fed before the start of the trial at 11.3 kg/d per cow after a 7-d diet acclimation period during which the cows were fed 3.8 kg/d per cow for 3 d, 7.5 kg/d per cow for 2 d, and 11.3 kg/d per cow for the final 2 d. The diet consisted of 84.5% whole corn, 7.5% cottonseed hulls, 7.5% CP pellet, and 0.05% trace minerals. The diet was formulated to provide, on a DM basis, 75.1% TDN, 11.9% CP, 6.5% crude fiber, 3.3% crude fat, 9.9% ADF, 16.1% NDF, 0.17% Ca and 0.28% P (NRC, 1996). During the one-week acclimation period, 0-d cows were pastured on common bahiagrass. Cows had ad libitum access to a mineral supplement (Nutrebeef, Nutrena, Cargill Inc., Minneapolis, MN) in a covered mineral feeder. Individual BW and BCS were recorded on d 0, 42, and 84. On d 0 of the study the first group of cows was transported 3.22 km to the Univer-
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sity of Florida Meats Processing Center (Gainesville, FL) for slaughter.
Carcass and Muscle Treatment At the end of each feeding period, the respective cows were transported 3.22 km to the University of Florida Meats Processing Center (Gainesville, FL) for slaughter. Cows were held without feed but were allowed ad libitum access to water for the final 24 h before slaughter. Following slaughter, individual hot carcass weights (HCW) were recorded before carcasses were chilled (0°C). After a 24-h chill, the left side of each carcass was ribbed at the 12th to 13th rib juncture and allowed to bloom for 30 min before carcass data collection. Quantitative carcass data collected included HCW, DP, ribeye area (REA), fat thickness (FT), lean maturity, bone maturity, and marbling. Subjectively scored carcass data included lean texture (1 = very fine, 2 = fine, 3 = slightly fine, 4 = slightly course, and 5 = course), lean firmness (1 = very firm, 2 = firm, 3 = slightly firm, 4 = slightly soft, and 5 = soft), and muscle score based on European Union beef carcass classification system (MLC, 2002). Objective color (L* measures lightness where 0 = black and 100 = white; a* measures the red to green spectrum where positive numbers are more red and negative numbers are more green; and b* measures the yellow to blue spectrum where positive numbers are more yellow and negative numbers are more blue) of lean and fat was measured with a Minolta Chromo Meter (CR-310; Minolta Co. Ltd., Osaka, Japan) with illuminant D65, 2° viewing angle, and 50-mm diameter measuring area. The Minolta was calibrated against a standard white tile each day before data collection. Subjective color score (1 = extremely dark red, 2 = dark red, 3 = moderately dark red, 4 = slightly dark cherry red, 5 = slightly bright cherry red, 6 = moderately bright cherry red, 7 = bright cherry red, and 8 = extremely bright cherry red) and objective color measurements were taken on the LM at the 12th to 13th
336 rib juncture. Additionally, fat color scores (1 = while, 2 = creamy white, 3 = slightly yellow, 4 = moderately yellow, and 5 = yellow) were representative of the external fatness of the entire carcass, whereas objective fat color was measured 5 cm distal of the chine bone opposite the longissimus lumborum (LL). The right side of each carcass was fabricated according to the North American Meat Processors Association (NAMP) specifications, and the triceps brachii long head (LON) and lateral head and infraspinatus (IF) were removed from the wholesale chuck (NAMP #113). The LL and psoas major (PS), as well as the gluteus medius (GM), were removed from the short-loin (NAMP #174) and sirloin (NAMP #184), respectively, and the tensor fascia latae, rectus femoris (RF), and vastus lateralis were removed from the wholesale round (NAMP #158). Muscles were trimmed to 0.0-cm fat and denuded of all visible surface connective tissues. The IF was separated medially and longitudinally, and the thick medial sheet of connective tissue was removed.
Collagen Analysis After carcass fabrication, one 2.54-cm thick steak was cut from the LL and LON for collagen analysis. Steaks were labeled, vacuumpackaged, and immediately stored at −40°C until analyses were conducted. Heat labile, soluble, insoluble and total collagen content for the LL and LON were extracted and separated following the methods outlined by Hill (1966). Duplicate 5-g samples from each muscle were mixed with 0.25-strength Ringer’s solution (0.86% NaCl, 0.03% KCl, and 0.02% CaCl2) and heated in a 77°C water bath for 63 min. Samples were then placed in a centrifuge at 13,200 × g for 20 min at 4°C. The supernatant was decanted and the pellet fraction was recentrifuged in 0.25-strength Ringer’s solution at 13, 200 × g for an additional 20 min. Again, the supernatant was decanted with the previous supernatant and marked as the
Stelzleni et al.
soluble collagen fraction. The residue pellet was combined with 25 mL of 6 M HCL and labeled as the insoluble collagen fraction. The supernatant was combined with 20 mL of 12 M HCL and placed in an autoclave at 103.42 kPa and 121°C for 18 h to hydrolyze the proteins. All samples were then filtered with 2 g of 1:2 charcoal:Lewatit Monoplus MP500 (Sigma-Aldrich, St. Louis, MO), and subsequently filtered through Whatman #41 filter paper, evaporated, and neutralized with distilled water and 3 N NaOH to a pH of 6.5. Hydroxyproline determination was carried out following the procedures outlined by Bergman and Loxley (1963) using a Jasco V-530 spectrophotometer and VWS 580 Spectra Manager for Windows (Tokyo, Japan) to read absorbance at 558 nm. The spectrophotometer was calibrated using a distilled water blank sample, and readings were determined by standard curves prepared for each day of analysis. Total and fractional collagen content was determined by multiplying the hydroxyproline content of the soluble supernatant by 7.25 and the residual insoluble fraction hydroxyproline content by 7.52 (Cross et al., 1973).
Warner-Bratzler Shear Force After carcass fabrication, 2 steaks were cut 2.54-cm thick perpendicular to muscle fiber orientation from all 9 muscles and subsequently labeled and vacuum-packaged (B-620 series; 30 to 50 mL O2/m2 per 24 h; 101325 Pa; 23°C; Cryovac, Duncan, SC) using a Mutivac C500 (Multivac Inc., Kansas City, MO) vacuum packager. Steaks were then allowed to age for either 10 or 20 d postmortem at 2°C. At the end of the required aging period, steaks were frozen and stored at −40°C until cooking. Steaks were allowed to thaw for 18 h at 4°C before being cooked on Farberware Open-Hearth Broilers (Farberware Products, Nashville, TN) preheated for 20 min. Steaks were turned once when the internal temperature reached 35°C and then were allowed to finish cooking until
they reached an internal temperature of 71°C (AMSA, 1995). Internal temperatures were monitored by copper-constantan thermocouples (Omega Engineering Inc., Stamford, CT) placed in the geometric center of each steak and recorded using a 1100 Labtech Notebook for Windows 1998 (Computer Boards Inc., Middleboro, MA). Steaks were allowed to cool for 18 h at 4°C before six 1.27-cm diameter cores were removed parallel to the longitudinal orientation of the muscle fibers. Cores were sheared once perpendicular to the longitudinal orientation of the muscle fibers with a Warner-Bratzler shear head attached to an Instron Universal Testing machine (Instron Corp., Canton, MA) with a crosshead speed of 200 mm/min.
Sensory Attributes Four 2.54-cm-thick steaks were cut from the LON, LL, GM, and RF across the grain of the muscle for sensory panel evaluation. Steaks were labeled, vacuum-packaged, and allowed to age in a 2°C cooler for either 10 or 20 d postmortem. At the end of the assigned aging period, steaks were stored at −40°C until further analysis could be completed. Sensory steaks were treated and cooked to the same specifications as were Warner-Bratzler shear force (WBS) samples. Upon reaching 71°C internal temperature, steaks were served to panelists warm. Sensory panelists evaluated 6 samples (two 1.27-cm3 cubes/steak) served in warmed covered containers in a positive pressure ventilation room with cubicles designed for objective meat sensory panels. Sampling was designed so that at each sensory session, each panelist was served samples, in random order, from 0, 42, and 84 d treatments and 10 and 20-d aged muscle within a carcass. An 11-member sensory panel trained according to AMSA sensory evaluation guidelines (AMSA, 1995) evaluated each sample for overall tenderness, overall juiciness, and beef flavor intensity (1 = extremely tough, dry, and bland; 2 = very tough, dry, and
Carcass attributes of concentrate-fed cull beef cows
bland; 3 = moderately tough, dry, and bland; 4 = slightly tough, dry, and bland; 5 = slightly tender, juicy, and intense; 6 = moderately tender, juicy, and intense; 7 = very tender, juicy, and intense; and 8 = extremely tender, juicy, and intense), as well as off-flavor (1 = extreme off-flavor, 2 = strong off-flavor, 3 = moderate off-flavor, 4 = slight off-flavor, 5 = threshold off-flavor, and 6 = no offflavor detected).
Statistical Analysis Data were analyzed using the MIXED procedures of SAS V.9.1 (2002, SAS Inst. Inc., Cary, NC), and means were separated by the PDIFF option in LSMEANS for all analyses. Data for live and carcass traits were analyzed with animal or carcass as the experimental unit and random variable. For collagen analysis, muscle within carcass was the random variable. For WBS and sensory analysis steak was considered the experimental unit, and steak within muscle was considered the random variable. Differences among means were considered significant at P ≤ 0.05.
RESULTS AND DISCUSSION Live and Carcass Characteristics Neither ADG nor BW differed (P > 0.10) between cows fed for 0 or 42 d; however, cows fed for 84 d had greater (P < 0.01) ADG and BW than cows fed 0 or 42 d (Table 1). Cows fed for 42 d had a greater (P < 0.05) BCS than cows slaughtered initially (0 d on concentrate), and BCS continued to increase (P < 0.05) when cows were fed for 84 d. Cows fed for 42 d exhibited a 0.7 unit increase in BCS from their initial score, whereas cows fed for 84 d exhibited a 1.6 unit increase in BCS during the entire realimentation period. Boleman et al. (1996) reported that BW increased for cull cows fed a concentrate diet for 28, 56, and 84 d, and Cranwell et al. (1996b) also reported increased cull cow BW as time on
feed increased over 0, 28, and 56 d. Similar to the current study, Apple (1999) reported that cull cow BW increased as BCS increased from 5 to 6. In contrast, Faulkner et al. (1989) reported an increase in cull cow BW from 0 to 42 d on concentrate, but observed no further BW increase from 42 to 84 d, with ADG of 2.74 and 1.60 kg, respectively. The difference in BW recorded for the current study is attributed to the low ADG observed for the cows fed for 42 d and the increased ADG observed for the cows fed for 84 d. Even though Faulkner et al. (1989) reported greater ADG during the first 42 d than the last 42 d (2.74 vs. 1.60 kg/d), cull cows fed 84 d gained more rapidly for the last 42 d than the first 42 d (0.75 kg/d vs. 1.23 kg/d) in the present study. Additionally, Matulis et al. (1987) reported that cull cows fed concentrate diets had the greatest ADG between 29 and 56 d and then had decreased ADG between 57 and 84 d. The reasons for the increased gains in the 84-d cull cows over the 42-d cows in the present study are not easily explained. One possibility could be the nutritional status of the cows entering the feeding trial. All cows were in a BCS of 4 or 5 at the beginning of the trial; therefore, large compensatory gains were not observed. Another possibility could be that the transition in diet from 100% forage to a highconcentrate diet (consisting of only 7.5% roughages) required a greater acclimation period than the 7 d allowed in the present trial. Sawyer et al. (2004) reported negative ADG and G:F for the first 14 d on concentrate, and they attributed the negative responses in live animal performance to a decrease in gut fill. This coupled with the previous reason could partially explain the low BW gains for cows during the first 42 d. Hot carcass weight did not (P > 0.05) differ between cows from 0 and 42 d on concentrate, but cows slaughtered after 84 d produced heavier (P < 0.01) carcasses than cows fed 0 or 42 d (Table 2). Dressing percent increased (P < 0.01) from 0 to 42 d but
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no additional increase was observed. The increased carcass DP of the cows on feed for 42 d could be explained by numerical increases in HCW, REA, FT, and carcass muscling, which could combine to provide an additive effect leading to the differences in DP observed after 42 d on feed. Although REA and carcass muscling were only different (P < 0.05) for carcasses from cows fed for 84 d compared with 0 or 42 d, numerical increases were observed in both traits by 42 d. Boleman et al. (1996) reported increased FT, REA, HCW, and YG as days on a concentrate diet increased to 84 d. Additionally, Cranwell et al. (1996b) reported increases in HCW, FT, REA, and YG as days on a concentrate diet increased from 0 to 56 d. Bone maturity did not (P > 0.30) differ among any of the 3 treatments; however, lean maturity was lower (P < 0.01) in carcasses from cows fed for 84 d than carcasses from cows fed 0 or 42 d (Table 2). Lean texture was not different (P > 0.05) among any of the treatments, but the lean became firmer (P < 0.05) in carcasses from cows fed for 84 d compared with carcasses from cows slaughtered initially (0 d on a concentrate diet). Marbling score increased (P < 0.01) in carcasses derived from cows fed for 84 d compared with carcasses from cows that were slaughtered directly off pasture; however, carcasses from cows fed for 42 d had a mean marbling score of Slight12, which did not differ (P > 0.10) from carcasses from cows fed 0 or 84 d. Carcasses from both 42- and 84-d treatments had QG that fell within USDA Utility QG, whereas carcasses from cows that were not fed had an average QG of USDA Cutter. The increase in QG from USDA Cutter to USDA Utility or greater may be enough of an increase in quality to add value to the carcasses from cull cows (Apple, 1999). Subjective lean color scores show that the lean became brighter and more cherry-red in color (P < 0.05) as days on a concentrate diet increased from 0 to 84 d (Table 2). The lean from carcasses of cows fed 42 d had
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Table 2. Least squares means for carcass characteristics of cull cows on a concentrate diet for 0, 42, or 84 d Days on feed Trait Hot carcass wt, kg DP Ribeye area, cm2 Fat thickness, cm Lean maturity Bone maturity Lean color Subjective1 L*2 a*2 b*2 Fat color Subjective3 L*2 a*2 b*2 Marbling4 Lean texture5 Lean firmness6 Muscling7 a-c
0d
42 d
84 d
SEM
229.3b 47.7b 64.35b 0.24b D 63a D 61
261.6b 53.4a 72.02ab 0.41b D 95a D 90
311.1a 54.8a 78.87a 0.95a C 60b E 14
12.61 1.15 2.89 0.11 20.39 26.15
5.3a 35.68c 24.48b 9.72b
4.9ab 37.75a 25.97a 10.66a
4.1b 36.97b 26.12a 10.50a
0.30 0.15 0.16 0.09
5.0c 78.85a 3.17c 27.92a 255b 4.5 3.8a 388b
3.9b 76.15b 9.90b 24.64b 312ab 4.3 2.6ab 488b
2.8a 74.13c 12.60a 22.70c 359a 3.8 2.4b 650a
0.29 0.55 0.57 0.55 23.93 0.28 0.37 53.31
Least squares means within a row with different superscripts differ (P < 0.05).
1
1 = extremely dark red, 2 = dark red, 3 = moderately dark red, 4 = slightly dark cherry red, 5 = slightly bright cherry red, 6 = moderately bright cherry red, 7 = bright cherry red, and 8 = extremely bright cherry red. 2
L* = measurement of lightness where 0 = black and 100 = white; a* = color measurement in the red to green spectrum where more positive numbers are in the red spectrum and more negative numbers are in the green spectrum; b* = color measurement in the yellow to blue spectrum where more positive numbers are in the yellow spectrum and more negative numbers are in the blue spectrum.
3
1 = white, 2 = creamy white, 3 = slightly yellow, 4 = moderately yellow, and 5 = yellow.
4
100 = Practically devoid, 200 = Traces, 300 = Slight, 400 = Small, 500 = Modest, 600 = Moderate, 700 = Slightly abundant, and 800 = Moderately abundant.
5
1 = very fine, 2 = fine, 3 = slightly fine, 4 = slightly course, and 5 = course.
6
1 = very firm, 2 = firm, 3 = slightly firm, 4 = slightly soft, and 5 = soft.
7
100 = light-, 200 = lighto, 300 = light+ represents P; 400 = medium-, 500 = mediumo, 600 = medium+ represents O; and 700 = heavy-, 800 = heavyo, 900 = heavy+ represents R (MLC, 2002).
the greatest (P < 0.01) L* values, and the lean from cows slaughtered initially (0 d on a concentrate diet) had the lowest (P < 0.01) L* values. Additionally, the lean from cull cows fed 84 d was lighter (P < 0.01) than the lean from cull cows in the 0-d onfeed group. Lean became redder (P < 0.01) and more yellow (P < 0.01) in color after 42 d on feed, but no additional improvements in instrumental
color were noted after 84 d on feed. Subjective fat color scores indicated that carcass fat became whiter (P < 0.01) as days on a concentrate diet increased from 0 to 84 d, whereas L* and b* values of subcutaneous fat decreased (P = 0.02), and a* values increased (P < 0.01) as days on a concentrate diet increased from 0 to 42 d and 42 to 84 d. Hilton et al. (1998) reported that fat color can be
correlated to other sensory traits, with yellow fat being indicative of decreased tenderness and increased off-flavors.
Collagen Content There was not (P > 0.01) a days on concentrate × muscle interaction for total collagen content; however, the LON had more (P < 0.01) soluble, insoluble, and total collagen than the LL (Table 3). Conversely, there was no difference (P > 0.50) in percent soluble or percent insoluble collagen between LON and LL. Additionally, percent soluble collagen and soluble collagen content did not (P > 0.20) differ between 0 and 42 d, but soluble collagen increased 40% by feeding cows a high-concentrate diet for 84 d. Even though total collagen content and insoluble collagen content were not (P > 0.05) affected by days on a concentrate diet, percent insoluble collagen decreased (P < 0.01) after cull cows were on feed for 84 d, likely due to the increase in the soluble collagen fraction. Boleman et al. (1996) and Cranwell et al. (1996a) both reported increases in percent soluble collagen as time on feed increased. Aberle et al. (1981) concluded that cattle fed high-energy diets experience rapid rates of protein synthesis and, therefore, would be expected to produce beef with a high proportion of newly synthesized, heat-liable collagen.
Warner-Bratzler Shear Force There were no days on concentrate × muscle × aging period (P > 0.80) or days on concentrate × aging period (P > 0.60) interactions for WBS; therefore, data were pooled to examine the days on concentrate × muscle interaction (P = 0.01) presented in Table 4. There was no difference (P > 0.05) in WBS values between treatments for IF, triceps brachii lateral head, PS, RF, and tensor fascia latae. The WBS values for the GM did not (P > 0.20) differ between cows fed for 0 and 42 d, but WBS decreased in the GM of cows slaughtered after 84 d. Shear force values actually increased
Carcass attributes of concentrate-fed cull beef cows
Table 3. Collagen content least squares means for the main effect of days on feed of muscles (longissimus lumborum and triceps brachii long head) from cull cows on a concentrate diet for 0, 42, or 84 d Days on feed Trait Total, mg/g Soluble, mg/g Insoluble, mg/g Soluble,1 % Insoluble,1 % a,b 1
0d
42 d
84 d
SEM
3.64 0.09b 3.54 2.69b 97.31a
2.73 0.09b 2.64 3.32b 96.68a
3.01 0.15a 2.85 5.48a 94.52b
0.32 0.01 0.31 0.36 0.36
Least squares means within a row with different superscripts differ (P < 0.05).
Expressed as a percent of total collagen.
(P < 0.05) in the LON during the first 42 d, but WBS values for the LON from cows slaughtered after 84 d were intermediate to the 0 and 42 d groups. Warner-Bratzler shear force values for the vastus lateralis were lowest (P < 0.05) in cows slaughtered initially (0 d on a concentrate diet) and greatest (P < 0.05) in cows fed 84 d, whereas WBS values for the LL decreased 3.7 kg between 0 and 84 d. For cows that did not receive concentrate feed before slaughter,
the LL was the least tender (P < 0.01) muscle, whereas after 42 d, the vastus lateralis had the lowest (P < 0.05) WBS values. Although the LL did not (P < 0.05) differ from the GM, triceps brachii lateral head, and LON, WBS values for the LL were greater (P < 0.01) than for the IF, PS, and RF. The PS and IF had lower (P < 0.01) WBS values than all the other muscles when cows were fed for 84 d.
Table 4. Least squares means for Warner-Bratzler shear force (in kilograms) interaction of treatment by muscle of muscles from cull cows on a concentrate diet for 0, 42, or 84 d1 Days on feed Muscle2 GM IF LAT LON LL PS RF TFL VL
0d
42 d
84 d
6.09avw 3.37az 5.28awx 5.32bwx 9.00au 3.17az 4.32ay 4.78axy 6.79bv
6.59aw 3.25az 6.02awx 6.26awx 6.15bwx 2.78az 4.63ay 5.65ax 7.54abv
4.61by 3.62az 5.54ax 5.61abx 5.30bxy 3.19az 5.25axy 5.21axy 7.79aw
a,b
Least squares means within a row with different superscripts differ (P < 0.05).
u-z
Least squares means within a column with different superscripts differ (P < 0.05).
1
Standard error of least squares means for all treatment by muscle interactions = 0.33.
2
GM = gluteus medius, IF = infraspinatus, LAT = triceps brachii lateral head, LON = triceps brachii long head, LL = longissimus lumborum, PS = psoas major, RF = rectus femoris, TFL = tensor fasciae latae, and VL = vastus lateralis.
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Most of the current literature on muscle characteristics of realimented cows was conducted on the LM (Matulis et al., 1987; Boleman et al., 1996; Cranwell et al., 1996a). Brown and Johnson (1991) reported that increased energy supplementation did not decrease shear force values for the LM in cull cows; however, Miller et al. (1987) demonstrated that increased energy supplementation before slaughter decreased longissimus shear force. Moreover, Matulis et al. (1987), Boleman et al. (1996), and Cranwell et al. (1996a) all reported that concentrate feeding of cull cows before slaughter decreased longissimus shear force. The improvements in WBS observed in the current study, as well as in many others’ research, may be partially attributed to an increase in heat-liable collagen (Table 3) that forms as a result of increases in lean accretion. Bailey (1985) suggested that old collagen is not completely catabolized, but, for the most part, is retained and pushed apart to allow expansion of newly synthesized collagen as lean accretion occurs; however, this would cause total collagen to increase, which was not seen in the present study. For muscles other than the longissimus, Dryden et al. (1979) reported that realimentation of cull cows before slaughter only improved the WBS of semimembranosus and biceps femoris after 108 d on a concentrate diet. Shear force values decreased (P < 0.01) 0.23 kg after 20 d of aging compared with steaks that were aged for 10 d (Table 5). Huff-Lonergan et al. (1995) reported the degradation of titin and nebulin occurred at a faster rate after 3 d postmortem in steaks from steers when compared with steaks from cows. Therefore, extended postmortem aging of cow beef, as in the current study, may be beneficial to maximize tenderness.
Sensory Attributes No difference (P > 0.30) was observed for overall tenderness scores between 0 and 42 d; however, overall tenderness scores increased (P <
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Table 5. Warner-Bratzler shear force and sensory attribute least squares means for the main effects of treatment and days of aging of muscles from cull cows on a concentrate diet for 0, 42, or 84 d Days on feed Trait
0d 1
Warner-Bratzler shear, kg Overall tenderness2 Beef flavor intensity2 Overall juiciness2 Off-flavor3 a,b
42 d a
84 d
a
5.35 4.27b 5.32 5.21 5.10b
Days of aging
a
5.43 4.47b 5.27 4.99 5.45a
5.13 4.99a 5.49 4.99 5.49a
SEM
10 d
20 d
y
0.17 0.13 0.07 0.09 0.05
SEM
z
5.42 4.47z 5.33 5.08 5.34
5.19 4.68y 5.39 5.05 5.36
0.11 0.08 0.05 0.07 0.04
Least squares means within a row with different superscripts differ (P < 0.05).
y,z
Least squares means in same row for days of aging with different superscripts differ (P < 0.05).
1
Days on feed × muscle interaction (P < 0.01).
2
1 = extremely tough, extremely bland, and extremely dry; 2 = very tough, very bland, and very dry; 3 = moderately tough, moderately bland, and moderately dry; 4 = slightly tough, slightly bland, and slightly dry; 5 = slightly tender, slightly intense, and slightly juicy; 6 = moderately tender, moderately intense, and moderately juicy; 7 = very tender, very intense, very juicy; and 8 = extremely tender, extremely intense, and extremely juicy. 1 = extreme off-flavor, 2 = strong off-flavor, 3 = moderate off-flavor, 4 = slight off-flavor, 5 = threshold off-flavor, and 6 = no off-flavor detected.
3
0.01) after 84 d (Table 5). Beef flavor intensity and overall juiciness were not affected (P > 0.05) by days on concentrate, yet sensory off-flavor detection decreased (P < 0.01) after 42 d. There were no interactive effects among postmortem aging period and either days on a concentrate diet or
muscle for any sensory attribute. Moreover, neither beef flavor intensity (P > 0.03) nor off-flavors (P > 0.06) differed between steaks aged 10 and 20 d. Steaks that were aged for 20 d were more (P < 0.01) tender than steaks aged for 10 d postmortem. Several authors have reported that endogenous enzymes, such as lysozo-
mal proteases and collagenases, have the ability to degrade connective tissues in beef when stored postmortem (Dutson et al., 1980; Wu et al., 1981), which would improve overall tenderness. The RF and GM were rated the most (P < 0.05) tender, whereas the LL was rated the least (P < 0.01)
Table 6. Warner-Bratzler shear force and sensory attribute least squares means for the main effect of muscle for cull cows that were on a concentrate diet for 0, 42, or 84 d Muscle1 Trait Warner-Bratzler shear,2 kg Overall tenderness3 Beef flavor intensity3 Overall juciness3 Off-flavor4
GM
IF
5.76c 3.41f 4.83a — 5.67a — 5.12 — 5.33ab —
LAT 5.61cd — — — —
LON 5.73c 4.57b 5.48b 5.07 5.48a
LL
PS
6.82b 3.05f 4.01c — 5.11c — 4.96 — 5.24b —
RF
TFL
4.73e 5.22de 4.90a — 5.03c — 5.11 — 5.33ab —
VL
SEM
7.37a — — — —
0.19 0.10 0.07 0.09 0.05
a-f
Least squares means within a row with different superscripts differ (P < 0.05).
1
GM = gluteus medius, IF = infraspinatus, LAT = triceps brachii lateral head, LON = triceps brachii long head, LL = longissimus lumborum, PS = psoas major, RF = rectus femoris, TFL = tensor fasciae latae, VL = vastus lateralis.
2
Days on feed × muscle interaction (P < 0.01).
3
1 = extremely tough, extremely bland, and extremely dry; 2 = very tough, very bland, and very dry; 3 = moderately tough, moderately bland, and moderately dry; 4 = slightly tough, slightly bland, and slightly dry; 5 = slightly tender, slightly intense, and slightly juicy; 6 = moderately tender, moderately intense, and moderately juicy; 7 = very tender, very intense, and very juicy; and 8 = extremely tender, extremely intense, and extremely juicy. 1 = extreme off-flavor, 2 = strong off-flavor, 3 = moderate off-flavor, 4 = slight off-flavor, 5 = threshold off-flavor, and 6 = no off-flavor detected.
4
Carcass attributes of concentrate-fed cull beef cows
tender of the 4 muscles examined (Table 6). The GM had the most (P < 0.05) intense beef flavor, and the LL and RF received the lowest ratings for beef flavor intensity, but all values were within the slightly intense range. There was no difference (P > 0.40) among muscles for overall juiciness score, and the LL was rated as having more (P < 0.01) off-flavor than the LON. Three of the 4 muscles examined (GM, LL, and LON) increased (P < 0.05) in sensory tenderness ratings as days on a concentrate diet increased, and the LL was rated the least (P < 0.01) tender muscle after 0 and 42 d but exhibited the greatest improvement in sensory tenderness rating, becoming similar to the LON and RF after 84 d. Dryden et al. (1979) reported an increase in sensory tenderness scores for the GM and biceps femoris from realimented cows.
IMPLICATIONS Results of this experiment indicate that concentrate feeding of cull cows before slaughter improved carcass characteristics and muscle quality attributes. Several muscles from the chuck and round were comparable to the LL in tenderness and sensory characteristics, which may lead to greater product utilization of these muscles, and ultimately, increased value of cull cows. Maximum carcass compositional changes were realized after cull cows were on feed for 84 d, and results of this study show that processors can age beef from cull cows at least 20 d without detrimental effects to beef flavor. More research is warranted examining mechanisms to alter lean and fat accretion levels in favor of lean accretion, which may aid in making concentrate feeding of cull cows a more efficient production practice.
LITERATURE CITED Aberle, E. D., E. S. Reeves, M. D. Judge, R. E. Hunsley, and T. W. Perry. 1981. Palatability and muscle characteristics of cattle
with controlled weight gain: Time on a high energy diet. J. Anim. Sci. 52:757. AMSA. 1995. Research Guidelines for Cookery, Sensory Evaluation, and Instrumental Tenderness Measurements of Fresh Meat. Am. Meat Sci. Assoc., Chicago, IL. Apple, J. K. 1999. Influence of body condition score on live and carcass value of cull beef cows. J. Anim. Sci. 77:2610. Apple, J. K., J. C. Davis, J. Stephenson, J. E. Hankins, J. R. Davis, and S. L. Beaty. 1999. Influence of body condition score on carcass characteristics and subprimal yield from cull beef cows. J. Anim. Sci. 77:2660. Bailey, A. J. 1985. The role of collagen in the development of muscle and its relationship to eating quality. J. Anim. Sci. 60:1580. Bergman, I., and R. Loxley. 1963. Two improved and simplified methods for the spectrophotometric determination of hydroxyproline. Anal. Chem. 35:1961. 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. Brown, W. F., and D. D. Johnson. 1991. Effects of energy and protein supplementation of ammoniated tropical grass hay on the growth and carcass characteristics of cull cows. J. Anim. Sci. 69:348. Cranwell, C. D., J. A. Unruh, J. R. Brethour, and D. D. Simms. 1996a. Influence of steroid implants and concentrate feeding on carcass and longissimus muscle sensory and collagen characteristics of cull beef cows. J. Anim. Sci. 74:1777. Cranwell, C. D., J. A. Unruh, J. R. Brethour, D. D. Simms, and R. E. Campbell. 1996b. Influence of steroid implants and concentrate feeding on performance and carcass composition of cull beef cows. J. Anim. Sci. 74:1770.
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Hill, F. 1966. The solubility of intramuscular collagen in meat animals of various ages. J. Food Sci. 31:161. Hilton, G. G., J. D. Tatum, S. E. Williams, K. E. Belk, F. L. Williams, J. W. Wise, and G. C. Smith. 1998. An evaluation of current and alternative systems for quality grading carcasses of mature slaughter cows. J. Anim. Sci. 76:2094. Huff-Lonergan, E., F. C. Parrish Jr, and R. M. Robson. 1995. Effects of postmortem aging time, animal age, and sex on degradation of titin and nebulin in bovine longissimus muscle. J. Anim. Sci. 73:1064. Matulis, R. J., F. K. McKeith, D. B. Faulkner, L. L. Berger, and P. George. 1987. Growth and carcass characteristics of cull cows after different times-on-feed. J. Anim. Sci. 65:669. Miller, M. F., H. R. Cross, J. D. Crouse, and T. G. Jenkins. 1987. Effect of feed energy intake on collagen characteristics and muscle quality of mature cows. Meat Sci. 21:287. MLC. 2002. Beef carcass authentication service leaflet. Meat and Livestock Commission, Milton Keynes, UK. http://store.mlc.org.uk/ index.asp?50479 Accessed Oct. 2, 2003. NCA. 1994. National Non-Fed Beef Quality Audit. Natl. Cattle Assoc., Englewood, CO. NCBA. 1999. Executive Summary of the 1999 National Market Cow and Bull Quality Audit. Natl. Cattle Beef Assoc., Englewood, CO. NRC. 1996. Nutrient Requirements of Beef Cattle. 7th ed. Natl. Acad. Press, Washington, DC. Richards, M. W., J. C. Spitzer, and M. B. Warner. 1986. Effect of varying levels of nutrition and body condition at calving on subsequent reproductive performance. J. Anim. Sci. 62:300.
Cross, H. R., Z. L. Carpenter, and G. C. Smith. 1973. Effects of intramuscular collagen and elastin on bovine muscle tenderness. J. Food Sci. 38:998.
Roeber, D. L., P. D. Mies, C. D. Smith, K. E. Belk, T. G. Field, J. D. Tatum, J. A. Scanga, and G. C. Smith. 2001. National market cow and bull beef quality audit–1999: A survey of producer-related defects in market cows and bulls. J. Anim. Sci. 79:658.
Dryden, F. D., J. A. Marchello, A. Tinsley, C. B. Martins, R. A. Wooten, C. B. Roubicek, and R. S. Swingle. 1979. Acceptability of selected muscles from poor condition and realimented cull range cows. J. Food Sci. 44:1058.
Sawyer, J. E., C. P. Mathis, and B. Davis. 2004. Effects of feeding strategy and age on live animal performance, carcass characteristics, and economics of short-term feeding programs for culled beef cows. J. Anim. Sci. 82:3646.
Dutson, T. R., G. C. Smith, and Z. L. Carpenter. 1980. Lysosomal enzyme distribution in electrically stimulated ovine muscle. J. Food Sci. 45:1097.
Swingle, S. 1979. Acceptability of selected muscles from poor condition and realimented cull range cows. J. Food Sci. 44:1058.
Faulkner, D. B., F. K. McKeith, L. L. Berger, D. J. Kesler, and D. F. Parrett. 1989. Effect of testosterone propionate on performance and carcass characteristics of heifers and cows. J. Anim. Sci. 67:1907.
Wu, J. J., T. R. Dutson, and Z. L. Carpenter. 1981. Effect of postmortem time and temperature on the release of cytosomal enzymes and their possible effect of bovine connective tissue components of muscle. J. Food Sci. 46:1132.
E fFeed fects of Days on Concentrate and Postmortem Aging on Carcass and Palatability Characteristics of Selected Muscles from Cull Beef Cows1 A. M. Stelzleni,2 D. D. Johnson, and T. A. Thrift Department of Animal Sciences, University of Florida, Gainesville 32611
ABSTRACT Twenty-four beef cows were selected to examine the effects of concentrate feeding on performance and to examine the effects of concentrate feeding and postmortem aging (10 or 20 d) on the triceps brachii lateral and long heads, infraspinatus, longissimus lumborum, psoas major, gluteus medius, tensor fascia latae, rectus femoris, and vastus lateralis. Cows were randomly assigned to a concentrate diet for 0, 42, or 84 d. Carcass characteristics were measured and Warner-Bratzler shear force, sensory evaluation, and collagen analyses were performed on selected muscles. Cow BW, ADG, and BCS increased (P < 0.02) after 84 d. Hot carcass weight, ribeye area, fat thickness, marbling, and muscling increased (P < 0.02) after 84 d. Soluble collagen content increased (P < 0.01) in the triceps brachii-long head and longissimus lumborum after 84 d. There was a days on concentrate × muscle interaction (P < 0.01) for Warner-Bratzler shear force with the 1 This research was funded in part by America’s beef producers through contributions made to the Beef Checkoff. 2 Corresponding author: [email protected]
longissimus lumborum and gluteus medius decreasing with increasing days. Sensory evaluation showed that steaks became more tender (P < 0.01) after 84 d and exhibited less (P < 0.01) off-flavor after 42 d. Extended postmortem aging (20 d) decreased (P < 0.01) WarnerBratzler shear force and increased (P < 0.01) sensory tenderness; however, postmortem aging did not increase (P > 0.05) sensory off-flavor detection. Concentrate feeding of cull cows for 84 d improved carcass characteristics and the tenderness of several muscles. These muscles may be aged for 20 d postmortem to achieve maximal tenderness without detrimental off-flavor production. Key words: concentrate feeding, cull cow, carcass characteristics, tenderness, palatability
INTRODUCTION Many of the cull cows entering the market are sold at a BCS of 4 or lower on a 9-point scale (NCBA, 1999). Increasing BCS to 6 before marketing may be advantageous to both producers and processors (Apple, 1999; Apple et al., 1999). Recent
cattle audits have identified several economical concerns for cull cow carcasses, including light muscling, low QG, light carcass weights, and yellow fat (NCA, 1994; Roeber et al., 2001). Short-term feeding is a practical management tool for achieving moderate BCS and improving carcass and quality characteristics. Shortterm feeding before slaughter has been known to decrease shear force values and increase sensory tenderness, soluble collagen content, and percent soluble collagen in the LM of cull beef cows (Miller et al., 1987). Short-term feeding after culling and before slaughter has also been shown to improve carcass and beef quality characteristics of cull cows (Brown and Johnson, 1991). However, little research has focused on the effects of realimentation on the quality of muscles other than the LM (Dryden et al., 1979). It was hypothesized that realimentation and postmortem aging would improve the quality and sensory characteristics of selected muscles from cull beef cow carcasses, thus increasing their utility beyond ground or comminuted products. Therefore, the objectives of this
Carcass attributes of concentrate-fed cull beef cows
Table 1. Least squares means of cull cow live traits before and after concentrate feeding for 0, 42, or 84 d Days on feed Item Age, yr Starting BCS1 Ending BCS1 Starting BW, kg Ending BW, kg ADG, kg/d a-c 1
0d 5.25 4.9 4.9c 491.3 491.3b 0.00b
42 d
84 d
SEM
5.50 4.7 5.4b 485.3 500.7b 0.37b
5.63 4.4 6.0a 497.8 581.1a 0.99a
0.47 0.20 0.17 20.86 22.96 0.16
Least squares means within a row with different superscripts differ (P < 0.05).
Richards et al., 1986.
research were to 1) determine the effects of realimentation on physical, chemical, and sensory characteristics of key muscles from cull beef cows; and 2) evaluate the effects of postmortem aging on various muscles from cull beef cows realimented for 0, 42 or 84 d.
MATERIALS AND METHODS The following research and protocols were reviewed and approved by the University of Florida Institutional Animal Care and Use Committee.
Animal Selection and Treatment Twenty-four beef cows were selected from the 2 University of Florida (Gainesville, FL) beef herds after being culled from the herds in late October due to failure to conceive after 2 consecutive years. Angus × Brahman cows were selected based upon the criterion that they previously had produced at least 2 calves. Cull cows selected for the experiment were weighed and assigned BCS (Richards et al., 1986) and were randomly allotted to 1 of 3 realimentation groups (n = 8 per group): 1) 0 d on concentrate feed, 2) 42 d on concentrate feed, and 3) 84 d on concentrate feed. Cow age, BCS, and BW were similar for all groups (Table 1), and all cows had been previously pastured on common Bahiagrass (Paspalum ssp.) and Ber-
mudagrass (Cynodon ssp.) throughout the summer and early fall. Cows that were fed for 42 and 84 d received pour-on anthelmintic (Eprinex-Ivomec, Merial, Iselin, New Jersey) at a rate of 10 mL/100 kg of BW, and were placed in a semidrylot environment allowing 0.06 ha per cow at the University of Florida Beef Teaching Unit (Gainesville, FL). All cows were fed as one group from bunks that allowed 1.0 m/cow of bunk space. Ad libitum access to water and shade canopy was provided at all times. Cows (42 and 84 d groups) were fed before the start of the trial at 11.3 kg/d per cow after a 7-d diet acclimation period during which the cows were fed 3.8 kg/d per cow for 3 d, 7.5 kg/d per cow for 2 d, and 11.3 kg/d per cow for the final 2 d. The diet consisted of 84.5% whole corn, 7.5% cottonseed hulls, 7.5% CP pellet, and 0.05% trace minerals. The diet was formulated to provide, on a DM basis, 75.1% TDN, 11.9% CP, 6.5% crude fiber, 3.3% crude fat, 9.9% ADF, 16.1% NDF, 0.17% Ca and 0.28% P (NRC, 1996). During the one-week acclimation period, 0-d cows were pastured on common bahiagrass. Cows had ad libitum access to a mineral supplement (Nutrebeef, Nutrena, Cargill Inc., Minneapolis, MN) in a covered mineral feeder. Individual BW and BCS were recorded on d 0, 42, and 84. On d 0 of the study the first group of cows was transported 3.22 km to the Univer-
335
sity of Florida Meats Processing Center (Gainesville, FL) for slaughter.
Carcass and Muscle Treatment At the end of each feeding period, the respective cows were transported 3.22 km to the University of Florida Meats Processing Center (Gainesville, FL) for slaughter. Cows were held without feed but were allowed ad libitum access to water for the final 24 h before slaughter. Following slaughter, individual hot carcass weights (HCW) were recorded before carcasses were chilled (0°C). After a 24-h chill, the left side of each carcass was ribbed at the 12th to 13th rib juncture and allowed to bloom for 30 min before carcass data collection. Quantitative carcass data collected included HCW, DP, ribeye area (REA), fat thickness (FT), lean maturity, bone maturity, and marbling. Subjectively scored carcass data included lean texture (1 = very fine, 2 = fine, 3 = slightly fine, 4 = slightly course, and 5 = course), lean firmness (1 = very firm, 2 = firm, 3 = slightly firm, 4 = slightly soft, and 5 = soft), and muscle score based on European Union beef carcass classification system (MLC, 2002). Objective color (L* measures lightness where 0 = black and 100 = white; a* measures the red to green spectrum where positive numbers are more red and negative numbers are more green; and b* measures the yellow to blue spectrum where positive numbers are more yellow and negative numbers are more blue) of lean and fat was measured with a Minolta Chromo Meter (CR-310; Minolta Co. Ltd., Osaka, Japan) with illuminant D65, 2° viewing angle, and 50-mm diameter measuring area. The Minolta was calibrated against a standard white tile each day before data collection. Subjective color score (1 = extremely dark red, 2 = dark red, 3 = moderately dark red, 4 = slightly dark cherry red, 5 = slightly bright cherry red, 6 = moderately bright cherry red, 7 = bright cherry red, and 8 = extremely bright cherry red) and objective color measurements were taken on the LM at the 12th to 13th
336 rib juncture. Additionally, fat color scores (1 = while, 2 = creamy white, 3 = slightly yellow, 4 = moderately yellow, and 5 = yellow) were representative of the external fatness of the entire carcass, whereas objective fat color was measured 5 cm distal of the chine bone opposite the longissimus lumborum (LL). The right side of each carcass was fabricated according to the North American Meat Processors Association (NAMP) specifications, and the triceps brachii long head (LON) and lateral head and infraspinatus (IF) were removed from the wholesale chuck (NAMP #113). The LL and psoas major (PS), as well as the gluteus medius (GM), were removed from the short-loin (NAMP #174) and sirloin (NAMP #184), respectively, and the tensor fascia latae, rectus femoris (RF), and vastus lateralis were removed from the wholesale round (NAMP #158). Muscles were trimmed to 0.0-cm fat and denuded of all visible surface connective tissues. The IF was separated medially and longitudinally, and the thick medial sheet of connective tissue was removed.
Collagen Analysis After carcass fabrication, one 2.54-cm thick steak was cut from the LL and LON for collagen analysis. Steaks were labeled, vacuumpackaged, and immediately stored at −40°C until analyses were conducted. Heat labile, soluble, insoluble and total collagen content for the LL and LON were extracted and separated following the methods outlined by Hill (1966). Duplicate 5-g samples from each muscle were mixed with 0.25-strength Ringer’s solution (0.86% NaCl, 0.03% KCl, and 0.02% CaCl2) and heated in a 77°C water bath for 63 min. Samples were then placed in a centrifuge at 13,200 × g for 20 min at 4°C. The supernatant was decanted and the pellet fraction was recentrifuged in 0.25-strength Ringer’s solution at 13, 200 × g for an additional 20 min. Again, the supernatant was decanted with the previous supernatant and marked as the
Stelzleni et al.
soluble collagen fraction. The residue pellet was combined with 25 mL of 6 M HCL and labeled as the insoluble collagen fraction. The supernatant was combined with 20 mL of 12 M HCL and placed in an autoclave at 103.42 kPa and 121°C for 18 h to hydrolyze the proteins. All samples were then filtered with 2 g of 1:2 charcoal:Lewatit Monoplus MP500 (Sigma-Aldrich, St. Louis, MO), and subsequently filtered through Whatman #41 filter paper, evaporated, and neutralized with distilled water and 3 N NaOH to a pH of 6.5. Hydroxyproline determination was carried out following the procedures outlined by Bergman and Loxley (1963) using a Jasco V-530 spectrophotometer and VWS 580 Spectra Manager for Windows (Tokyo, Japan) to read absorbance at 558 nm. The spectrophotometer was calibrated using a distilled water blank sample, and readings were determined by standard curves prepared for each day of analysis. Total and fractional collagen content was determined by multiplying the hydroxyproline content of the soluble supernatant by 7.25 and the residual insoluble fraction hydroxyproline content by 7.52 (Cross et al., 1973).
Warner-Bratzler Shear Force After carcass fabrication, 2 steaks were cut 2.54-cm thick perpendicular to muscle fiber orientation from all 9 muscles and subsequently labeled and vacuum-packaged (B-620 series; 30 to 50 mL O2/m2 per 24 h; 101325 Pa; 23°C; Cryovac, Duncan, SC) using a Mutivac C500 (Multivac Inc., Kansas City, MO) vacuum packager. Steaks were then allowed to age for either 10 or 20 d postmortem at 2°C. At the end of the required aging period, steaks were frozen and stored at −40°C until cooking. Steaks were allowed to thaw for 18 h at 4°C before being cooked on Farberware Open-Hearth Broilers (Farberware Products, Nashville, TN) preheated for 20 min. Steaks were turned once when the internal temperature reached 35°C and then were allowed to finish cooking until
they reached an internal temperature of 71°C (AMSA, 1995). Internal temperatures were monitored by copper-constantan thermocouples (Omega Engineering Inc., Stamford, CT) placed in the geometric center of each steak and recorded using a 1100 Labtech Notebook for Windows 1998 (Computer Boards Inc., Middleboro, MA). Steaks were allowed to cool for 18 h at 4°C before six 1.27-cm diameter cores were removed parallel to the longitudinal orientation of the muscle fibers. Cores were sheared once perpendicular to the longitudinal orientation of the muscle fibers with a Warner-Bratzler shear head attached to an Instron Universal Testing machine (Instron Corp., Canton, MA) with a crosshead speed of 200 mm/min.
Sensory Attributes Four 2.54-cm-thick steaks were cut from the LON, LL, GM, and RF across the grain of the muscle for sensory panel evaluation. Steaks were labeled, vacuum-packaged, and allowed to age in a 2°C cooler for either 10 or 20 d postmortem. At the end of the assigned aging period, steaks were stored at −40°C until further analysis could be completed. Sensory steaks were treated and cooked to the same specifications as were Warner-Bratzler shear force (WBS) samples. Upon reaching 71°C internal temperature, steaks were served to panelists warm. Sensory panelists evaluated 6 samples (two 1.27-cm3 cubes/steak) served in warmed covered containers in a positive pressure ventilation room with cubicles designed for objective meat sensory panels. Sampling was designed so that at each sensory session, each panelist was served samples, in random order, from 0, 42, and 84 d treatments and 10 and 20-d aged muscle within a carcass. An 11-member sensory panel trained according to AMSA sensory evaluation guidelines (AMSA, 1995) evaluated each sample for overall tenderness, overall juiciness, and beef flavor intensity (1 = extremely tough, dry, and bland; 2 = very tough, dry, and
Carcass attributes of concentrate-fed cull beef cows
bland; 3 = moderately tough, dry, and bland; 4 = slightly tough, dry, and bland; 5 = slightly tender, juicy, and intense; 6 = moderately tender, juicy, and intense; 7 = very tender, juicy, and intense; and 8 = extremely tender, juicy, and intense), as well as off-flavor (1 = extreme off-flavor, 2 = strong off-flavor, 3 = moderate off-flavor, 4 = slight off-flavor, 5 = threshold off-flavor, and 6 = no offflavor detected).
Statistical Analysis Data were analyzed using the MIXED procedures of SAS V.9.1 (2002, SAS Inst. Inc., Cary, NC), and means were separated by the PDIFF option in LSMEANS for all analyses. Data for live and carcass traits were analyzed with animal or carcass as the experimental unit and random variable. For collagen analysis, muscle within carcass was the random variable. For WBS and sensory analysis steak was considered the experimental unit, and steak within muscle was considered the random variable. Differences among means were considered significant at P ≤ 0.05.
RESULTS AND DISCUSSION Live and Carcass Characteristics Neither ADG nor BW differed (P > 0.10) between cows fed for 0 or 42 d; however, cows fed for 84 d had greater (P < 0.01) ADG and BW than cows fed 0 or 42 d (Table 1). Cows fed for 42 d had a greater (P < 0.05) BCS than cows slaughtered initially (0 d on concentrate), and BCS continued to increase (P < 0.05) when cows were fed for 84 d. Cows fed for 42 d exhibited a 0.7 unit increase in BCS from their initial score, whereas cows fed for 84 d exhibited a 1.6 unit increase in BCS during the entire realimentation period. Boleman et al. (1996) reported that BW increased for cull cows fed a concentrate diet for 28, 56, and 84 d, and Cranwell et al. (1996b) also reported increased cull cow BW as time on
feed increased over 0, 28, and 56 d. Similar to the current study, Apple (1999) reported that cull cow BW increased as BCS increased from 5 to 6. In contrast, Faulkner et al. (1989) reported an increase in cull cow BW from 0 to 42 d on concentrate, but observed no further BW increase from 42 to 84 d, with ADG of 2.74 and 1.60 kg, respectively. The difference in BW recorded for the current study is attributed to the low ADG observed for the cows fed for 42 d and the increased ADG observed for the cows fed for 84 d. Even though Faulkner et al. (1989) reported greater ADG during the first 42 d than the last 42 d (2.74 vs. 1.60 kg/d), cull cows fed 84 d gained more rapidly for the last 42 d than the first 42 d (0.75 kg/d vs. 1.23 kg/d) in the present study. Additionally, Matulis et al. (1987) reported that cull cows fed concentrate diets had the greatest ADG between 29 and 56 d and then had decreased ADG between 57 and 84 d. The reasons for the increased gains in the 84-d cull cows over the 42-d cows in the present study are not easily explained. One possibility could be the nutritional status of the cows entering the feeding trial. All cows were in a BCS of 4 or 5 at the beginning of the trial; therefore, large compensatory gains were not observed. Another possibility could be that the transition in diet from 100% forage to a highconcentrate diet (consisting of only 7.5% roughages) required a greater acclimation period than the 7 d allowed in the present trial. Sawyer et al. (2004) reported negative ADG and G:F for the first 14 d on concentrate, and they attributed the negative responses in live animal performance to a decrease in gut fill. This coupled with the previous reason could partially explain the low BW gains for cows during the first 42 d. Hot carcass weight did not (P > 0.05) differ between cows from 0 and 42 d on concentrate, but cows slaughtered after 84 d produced heavier (P < 0.01) carcasses than cows fed 0 or 42 d (Table 2). Dressing percent increased (P < 0.01) from 0 to 42 d but
337
no additional increase was observed. The increased carcass DP of the cows on feed for 42 d could be explained by numerical increases in HCW, REA, FT, and carcass muscling, which could combine to provide an additive effect leading to the differences in DP observed after 42 d on feed. Although REA and carcass muscling were only different (P < 0.05) for carcasses from cows fed for 84 d compared with 0 or 42 d, numerical increases were observed in both traits by 42 d. Boleman et al. (1996) reported increased FT, REA, HCW, and YG as days on a concentrate diet increased to 84 d. Additionally, Cranwell et al. (1996b) reported increases in HCW, FT, REA, and YG as days on a concentrate diet increased from 0 to 56 d. Bone maturity did not (P > 0.30) differ among any of the 3 treatments; however, lean maturity was lower (P < 0.01) in carcasses from cows fed for 84 d than carcasses from cows fed 0 or 42 d (Table 2). Lean texture was not different (P > 0.05) among any of the treatments, but the lean became firmer (P < 0.05) in carcasses from cows fed for 84 d compared with carcasses from cows slaughtered initially (0 d on a concentrate diet). Marbling score increased (P < 0.01) in carcasses derived from cows fed for 84 d compared with carcasses from cows that were slaughtered directly off pasture; however, carcasses from cows fed for 42 d had a mean marbling score of Slight12, which did not differ (P > 0.10) from carcasses from cows fed 0 or 84 d. Carcasses from both 42- and 84-d treatments had QG that fell within USDA Utility QG, whereas carcasses from cows that were not fed had an average QG of USDA Cutter. The increase in QG from USDA Cutter to USDA Utility or greater may be enough of an increase in quality to add value to the carcasses from cull cows (Apple, 1999). Subjective lean color scores show that the lean became brighter and more cherry-red in color (P < 0.05) as days on a concentrate diet increased from 0 to 84 d (Table 2). The lean from carcasses of cows fed 42 d had
Stelzleni et al.
338
Table 2. Least squares means for carcass characteristics of cull cows on a concentrate diet for 0, 42, or 84 d Days on feed Trait Hot carcass wt, kg DP Ribeye area, cm2 Fat thickness, cm Lean maturity Bone maturity Lean color Subjective1 L*2 a*2 b*2 Fat color Subjective3 L*2 a*2 b*2 Marbling4 Lean texture5 Lean firmness6 Muscling7 a-c
0d
42 d
84 d
SEM
229.3b 47.7b 64.35b 0.24b D 63a D 61
261.6b 53.4a 72.02ab 0.41b D 95a D 90
311.1a 54.8a 78.87a 0.95a C 60b E 14
12.61 1.15 2.89 0.11 20.39 26.15
5.3a 35.68c 24.48b 9.72b
4.9ab 37.75a 25.97a 10.66a
4.1b 36.97b 26.12a 10.50a
0.30 0.15 0.16 0.09
5.0c 78.85a 3.17c 27.92a 255b 4.5 3.8a 388b
3.9b 76.15b 9.90b 24.64b 312ab 4.3 2.6ab 488b
2.8a 74.13c 12.60a 22.70c 359a 3.8 2.4b 650a
0.29 0.55 0.57 0.55 23.93 0.28 0.37 53.31
Least squares means within a row with different superscripts differ (P < 0.05).
1
1 = extremely dark red, 2 = dark red, 3 = moderately dark red, 4 = slightly dark cherry red, 5 = slightly bright cherry red, 6 = moderately bright cherry red, 7 = bright cherry red, and 8 = extremely bright cherry red. 2
L* = measurement of lightness where 0 = black and 100 = white; a* = color measurement in the red to green spectrum where more positive numbers are in the red spectrum and more negative numbers are in the green spectrum; b* = color measurement in the yellow to blue spectrum where more positive numbers are in the yellow spectrum and more negative numbers are in the blue spectrum.
3
1 = white, 2 = creamy white, 3 = slightly yellow, 4 = moderately yellow, and 5 = yellow.
4
100 = Practically devoid, 200 = Traces, 300 = Slight, 400 = Small, 500 = Modest, 600 = Moderate, 700 = Slightly abundant, and 800 = Moderately abundant.
5
1 = very fine, 2 = fine, 3 = slightly fine, 4 = slightly course, and 5 = course.
6
1 = very firm, 2 = firm, 3 = slightly firm, 4 = slightly soft, and 5 = soft.
7
100 = light-, 200 = lighto, 300 = light+ represents P; 400 = medium-, 500 = mediumo, 600 = medium+ represents O; and 700 = heavy-, 800 = heavyo, 900 = heavy+ represents R (MLC, 2002).
the greatest (P < 0.01) L* values, and the lean from cows slaughtered initially (0 d on a concentrate diet) had the lowest (P < 0.01) L* values. Additionally, the lean from cull cows fed 84 d was lighter (P < 0.01) than the lean from cull cows in the 0-d onfeed group. Lean became redder (P < 0.01) and more yellow (P < 0.01) in color after 42 d on feed, but no additional improvements in instrumental
color were noted after 84 d on feed. Subjective fat color scores indicated that carcass fat became whiter (P < 0.01) as days on a concentrate diet increased from 0 to 84 d, whereas L* and b* values of subcutaneous fat decreased (P = 0.02), and a* values increased (P < 0.01) as days on a concentrate diet increased from 0 to 42 d and 42 to 84 d. Hilton et al. (1998) reported that fat color can be
correlated to other sensory traits, with yellow fat being indicative of decreased tenderness and increased off-flavors.
Collagen Content There was not (P > 0.01) a days on concentrate × muscle interaction for total collagen content; however, the LON had more (P < 0.01) soluble, insoluble, and total collagen than the LL (Table 3). Conversely, there was no difference (P > 0.50) in percent soluble or percent insoluble collagen between LON and LL. Additionally, percent soluble collagen and soluble collagen content did not (P > 0.20) differ between 0 and 42 d, but soluble collagen increased 40% by feeding cows a high-concentrate diet for 84 d. Even though total collagen content and insoluble collagen content were not (P > 0.05) affected by days on a concentrate diet, percent insoluble collagen decreased (P < 0.01) after cull cows were on feed for 84 d, likely due to the increase in the soluble collagen fraction. Boleman et al. (1996) and Cranwell et al. (1996a) both reported increases in percent soluble collagen as time on feed increased. Aberle et al. (1981) concluded that cattle fed high-energy diets experience rapid rates of protein synthesis and, therefore, would be expected to produce beef with a high proportion of newly synthesized, heat-liable collagen.
Warner-Bratzler Shear Force There were no days on concentrate × muscle × aging period (P > 0.80) or days on concentrate × aging period (P > 0.60) interactions for WBS; therefore, data were pooled to examine the days on concentrate × muscle interaction (P = 0.01) presented in Table 4. There was no difference (P > 0.05) in WBS values between treatments for IF, triceps brachii lateral head, PS, RF, and tensor fascia latae. The WBS values for the GM did not (P > 0.20) differ between cows fed for 0 and 42 d, but WBS decreased in the GM of cows slaughtered after 84 d. Shear force values actually increased
Carcass attributes of concentrate-fed cull beef cows
Table 3. Collagen content least squares means for the main effect of days on feed of muscles (longissimus lumborum and triceps brachii long head) from cull cows on a concentrate diet for 0, 42, or 84 d Days on feed Trait Total, mg/g Soluble, mg/g Insoluble, mg/g Soluble,1 % Insoluble,1 % a,b 1
0d
42 d
84 d
SEM
3.64 0.09b 3.54 2.69b 97.31a
2.73 0.09b 2.64 3.32b 96.68a
3.01 0.15a 2.85 5.48a 94.52b
0.32 0.01 0.31 0.36 0.36
Least squares means within a row with different superscripts differ (P < 0.05).
Expressed as a percent of total collagen.
(P < 0.05) in the LON during the first 42 d, but WBS values for the LON from cows slaughtered after 84 d were intermediate to the 0 and 42 d groups. Warner-Bratzler shear force values for the vastus lateralis were lowest (P < 0.05) in cows slaughtered initially (0 d on a concentrate diet) and greatest (P < 0.05) in cows fed 84 d, whereas WBS values for the LL decreased 3.7 kg between 0 and 84 d. For cows that did not receive concentrate feed before slaughter,
the LL was the least tender (P < 0.01) muscle, whereas after 42 d, the vastus lateralis had the lowest (P < 0.05) WBS values. Although the LL did not (P < 0.05) differ from the GM, triceps brachii lateral head, and LON, WBS values for the LL were greater (P < 0.01) than for the IF, PS, and RF. The PS and IF had lower (P < 0.01) WBS values than all the other muscles when cows were fed for 84 d.
Table 4. Least squares means for Warner-Bratzler shear force (in kilograms) interaction of treatment by muscle of muscles from cull cows on a concentrate diet for 0, 42, or 84 d1 Days on feed Muscle2 GM IF LAT LON LL PS RF TFL VL
0d
42 d
84 d
6.09avw 3.37az 5.28awx 5.32bwx 9.00au 3.17az 4.32ay 4.78axy 6.79bv
6.59aw 3.25az 6.02awx 6.26awx 6.15bwx 2.78az 4.63ay 5.65ax 7.54abv
4.61by 3.62az 5.54ax 5.61abx 5.30bxy 3.19az 5.25axy 5.21axy 7.79aw
a,b
Least squares means within a row with different superscripts differ (P < 0.05).
u-z
Least squares means within a column with different superscripts differ (P < 0.05).
1
Standard error of least squares means for all treatment by muscle interactions = 0.33.
2
GM = gluteus medius, IF = infraspinatus, LAT = triceps brachii lateral head, LON = triceps brachii long head, LL = longissimus lumborum, PS = psoas major, RF = rectus femoris, TFL = tensor fasciae latae, and VL = vastus lateralis.
339
Most of the current literature on muscle characteristics of realimented cows was conducted on the LM (Matulis et al., 1987; Boleman et al., 1996; Cranwell et al., 1996a). Brown and Johnson (1991) reported that increased energy supplementation did not decrease shear force values for the LM in cull cows; however, Miller et al. (1987) demonstrated that increased energy supplementation before slaughter decreased longissimus shear force. Moreover, Matulis et al. (1987), Boleman et al. (1996), and Cranwell et al. (1996a) all reported that concentrate feeding of cull cows before slaughter decreased longissimus shear force. The improvements in WBS observed in the current study, as well as in many others’ research, may be partially attributed to an increase in heat-liable collagen (Table 3) that forms as a result of increases in lean accretion. Bailey (1985) suggested that old collagen is not completely catabolized, but, for the most part, is retained and pushed apart to allow expansion of newly synthesized collagen as lean accretion occurs; however, this would cause total collagen to increase, which was not seen in the present study. For muscles other than the longissimus, Dryden et al. (1979) reported that realimentation of cull cows before slaughter only improved the WBS of semimembranosus and biceps femoris after 108 d on a concentrate diet. Shear force values decreased (P < 0.01) 0.23 kg after 20 d of aging compared with steaks that were aged for 10 d (Table 5). Huff-Lonergan et al. (1995) reported the degradation of titin and nebulin occurred at a faster rate after 3 d postmortem in steaks from steers when compared with steaks from cows. Therefore, extended postmortem aging of cow beef, as in the current study, may be beneficial to maximize tenderness.
Sensory Attributes No difference (P > 0.30) was observed for overall tenderness scores between 0 and 42 d; however, overall tenderness scores increased (P <
Stelzleni et al.
340
Table 5. Warner-Bratzler shear force and sensory attribute least squares means for the main effects of treatment and days of aging of muscles from cull cows on a concentrate diet for 0, 42, or 84 d Days on feed Trait
0d 1
Warner-Bratzler shear, kg Overall tenderness2 Beef flavor intensity2 Overall juiciness2 Off-flavor3 a,b
42 d a
84 d
a
5.35 4.27b 5.32 5.21 5.10b
Days of aging
a
5.43 4.47b 5.27 4.99 5.45a
5.13 4.99a 5.49 4.99 5.49a
SEM
10 d
20 d
y
0.17 0.13 0.07 0.09 0.05
SEM
z
5.42 4.47z 5.33 5.08 5.34
5.19 4.68y 5.39 5.05 5.36
0.11 0.08 0.05 0.07 0.04
Least squares means within a row with different superscripts differ (P < 0.05).
y,z
Least squares means in same row for days of aging with different superscripts differ (P < 0.05).
1
Days on feed × muscle interaction (P < 0.01).
2
1 = extremely tough, extremely bland, and extremely dry; 2 = very tough, very bland, and very dry; 3 = moderately tough, moderately bland, and moderately dry; 4 = slightly tough, slightly bland, and slightly dry; 5 = slightly tender, slightly intense, and slightly juicy; 6 = moderately tender, moderately intense, and moderately juicy; 7 = very tender, very intense, very juicy; and 8 = extremely tender, extremely intense, and extremely juicy. 1 = extreme off-flavor, 2 = strong off-flavor, 3 = moderate off-flavor, 4 = slight off-flavor, 5 = threshold off-flavor, and 6 = no off-flavor detected.
3
0.01) after 84 d (Table 5). Beef flavor intensity and overall juiciness were not affected (P > 0.05) by days on concentrate, yet sensory off-flavor detection decreased (P < 0.01) after 42 d. There were no interactive effects among postmortem aging period and either days on a concentrate diet or
muscle for any sensory attribute. Moreover, neither beef flavor intensity (P > 0.03) nor off-flavors (P > 0.06) differed between steaks aged 10 and 20 d. Steaks that were aged for 20 d were more (P < 0.01) tender than steaks aged for 10 d postmortem. Several authors have reported that endogenous enzymes, such as lysozo-
mal proteases and collagenases, have the ability to degrade connective tissues in beef when stored postmortem (Dutson et al., 1980; Wu et al., 1981), which would improve overall tenderness. The RF and GM were rated the most (P < 0.05) tender, whereas the LL was rated the least (P < 0.01)
Table 6. Warner-Bratzler shear force and sensory attribute least squares means for the main effect of muscle for cull cows that were on a concentrate diet for 0, 42, or 84 d Muscle1 Trait Warner-Bratzler shear,2 kg Overall tenderness3 Beef flavor intensity3 Overall juciness3 Off-flavor4
GM
IF
5.76c 3.41f 4.83a — 5.67a — 5.12 — 5.33ab —
LAT 5.61cd — — — —
LON 5.73c 4.57b 5.48b 5.07 5.48a
LL
PS
6.82b 3.05f 4.01c — 5.11c — 4.96 — 5.24b —
RF
TFL
4.73e 5.22de 4.90a — 5.03c — 5.11 — 5.33ab —
VL
SEM
7.37a — — — —
0.19 0.10 0.07 0.09 0.05
a-f
Least squares means within a row with different superscripts differ (P < 0.05).
1
GM = gluteus medius, IF = infraspinatus, LAT = triceps brachii lateral head, LON = triceps brachii long head, LL = longissimus lumborum, PS = psoas major, RF = rectus femoris, TFL = tensor fasciae latae, VL = vastus lateralis.
2
Days on feed × muscle interaction (P < 0.01).
3
1 = extremely tough, extremely bland, and extremely dry; 2 = very tough, very bland, and very dry; 3 = moderately tough, moderately bland, and moderately dry; 4 = slightly tough, slightly bland, and slightly dry; 5 = slightly tender, slightly intense, and slightly juicy; 6 = moderately tender, moderately intense, and moderately juicy; 7 = very tender, very intense, and very juicy; and 8 = extremely tender, extremely intense, and extremely juicy. 1 = extreme off-flavor, 2 = strong off-flavor, 3 = moderate off-flavor, 4 = slight off-flavor, 5 = threshold off-flavor, and 6 = no off-flavor detected.
4
Carcass attributes of concentrate-fed cull beef cows
tender of the 4 muscles examined (Table 6). The GM had the most (P < 0.05) intense beef flavor, and the LL and RF received the lowest ratings for beef flavor intensity, but all values were within the slightly intense range. There was no difference (P > 0.40) among muscles for overall juiciness score, and the LL was rated as having more (P < 0.01) off-flavor than the LON. Three of the 4 muscles examined (GM, LL, and LON) increased (P < 0.05) in sensory tenderness ratings as days on a concentrate diet increased, and the LL was rated the least (P < 0.01) tender muscle after 0 and 42 d but exhibited the greatest improvement in sensory tenderness rating, becoming similar to the LON and RF after 84 d. Dryden et al. (1979) reported an increase in sensory tenderness scores for the GM and biceps femoris from realimented cows.
IMPLICATIONS Results of this experiment indicate that concentrate feeding of cull cows before slaughter improved carcass characteristics and muscle quality attributes. Several muscles from the chuck and round were comparable to the LL in tenderness and sensory characteristics, which may lead to greater product utilization of these muscles, and ultimately, increased value of cull cows. Maximum carcass compositional changes were realized after cull cows were on feed for 84 d, and results of this study show that processors can age beef from cull cows at least 20 d without detrimental effects to beef flavor. More research is warranted examining mechanisms to alter lean and fat accretion levels in favor of lean accretion, which may aid in making concentrate feeding of cull cows a more efficient production practice.
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