- Email: [email protected]
Feeding Ractopamine Hydrochloride to Cull Cows: Effects on Carcass Composition, Warner-Bratzler Shear Force, and Yield
The Professional Animal Scientist 24 (2008):634–638 ©2008 American Registry of Professional Animal Scientists
C Ractopamine S : Feeding Hydrochloride to ase
tudy
Cull Cows: Effects on Carcass Composition, Warner-Bratzler Shear Force, and Yield R. D. Dijkhuis,*1 D. D. Johnson,* and J. N. Carter† *Department of Animal Sciences, University of Florida, Gainesville, 32611; and †North Florida Research and Education Center, University of Florida, Marianna 32446
ABSTRACT Culled beef cows (n = 95, 10.5 ± 1.2 yr), were randomly sorted into 1 of 4 pens based on level of ractopamine (RAC) supplementation including control (no RAC), 100, 200, or 300 mg/d of RAC for the final 30 d of a 48-d feeding period. At 24 h postmortem, carcass data were collected, carcasses were fabricated, and 9 muscles (adductor, gracilis, infraspinatus, longissimus thoracicus, rectus femoris, semimembranosus, teres major, triceps brachii, and vastus lateralis) were removed. The triceps brachii was further separated into the long and lateral heads. Feeding RAC had little effect on carcass characteristics or Warner-Bratzler shear force (P > 0.05) at any treatment level. Percentage of fatfree lean increased (P < 0.05) for RAC at 300 mg when compared with controlfed. Overall, feeding RAC had little to no effect on carcass characteristics. This study shows that producers feeding RAC to cull cows will not directly benefit from increased carcass performance compared with cull cows not supplemented with
1
Corresponding author: [email protected]
RAC. In contrast, packers will indirectly benefit from cull cows being fed RAC at 300 mg/d per head for the final 30 d of a 48-d feeding period due to the increase in percent fat-free lean. Key words: carcass composition, cull cows, ractopamine, Warner-Bratzler shear force, yield
INTRODUCTION Cull cows, a byproduct of the beef cow-calf industry, can represent 10 to 20% of a producer’s income (Sawyer et al., 2004). Often times cull cows are marketed due to health or structural related problems or because they did not conceive. Cull cows are typically marketed when they are in poor body condition, resulting in less than optimal revenues at sale. Previous research has shown that feeding cull cows a concentrate diet will increase hot carcass weights (HCW), longissimus muscle area, intramuscular fat (IMF), subcutaneous fat, and fat-free soft tissue (Wooten et al., 1979; Matulis et al., 1987; Miller et al., 1987; Faulkner et al., 1989; Cranwell et al., 1996b; Schnell
et al., 1997; Gonzalez et al., 2007; Jurie et al., 2007; Stelzleni et al., 2007). Supplementation with a type I β-adrenergic receptor agonist (ractopamine-HCl; RAC) increases protein accretion 25 to 30% at the expense of fat storage (Mersmann, 1998; Bridge et al., 1998). Also, Eisemann et al. (1988) reported that dosage level and dose duration of β agonists can influence receptor expression. The objective of this study was to determine whether feeding increased dietary levels of RAC for 30 d will increase lean accretion and decrease fat accretion, therefore increasing total lean yields of cull cows.
MATERIALS AND METHODS Experimental Animals Two truckloads (n = 48 each; 10.5 ± 1.2 yr) of cull crossbred cows (predominately Beefmaster and Brangus) were transported from a commercial cow-calf operation in south Florida (Okeechobee, FL) to a designated feeding facility in Williston, FL. Upon arrival, cows were weighed and treated with a pour-on endectocide (Decto-
Ractopamine hydrochloride effect on cull cow composition
max Pfizer Inc., New York, NY). Cull cows were randomly assigned to 1 of 4 treatments for the final 30 d of feeding consisting of control (CON; no supplemental RAC), RAC 100 (100 mg RAC/d per head), RAC 200 (200 mg RAC/d per head), and RAC 300 (300 mg RAC/d per head). Each treatment group was penned and fed together ad libitum from a self-feeder for a total of 48 d including RAC supplementation. The basal diet was comprised of the following ingredients: soybean hulls, citrus pulp, cracked corn, wheat middlings, cottonseed hulls, cottonseed meal, molasses, tallow, and urea. The diet contained approximately 87.6% DM, 14% CP (DM basis), and 79.5% TDN. On d 49, cows were transported to a commercial slaughter facility (Central Packing, Center Hill, FL) and harvested in a conventional manner.
Muscle Sample Preparation and CIE (Comission Internationale de l’Eclairage) L*, a*, and b* Color At 24 h postmortem, carcasses were fabricated and 9 muscles [adductor; gracilis (GRA); infraspinatus (INF); longissimus thoracicus (LM); rectus femoris (REF); semimembranosus (SMB); teres major (TEM); triceps brachii, lateral and long heads (TRB, TRBlat and TRBlong); and vastus lateralis] were removed and transported to the University of Florida’s Meat Processing Center (Gainesville, FL). Commodity (0.64 cm fat trim level) weights were recorded from the selected muscles, which were then trimmed to a zero (0.0 cm) fat level to determine denuded weights. During the denuding process, the TRB was further separated in lateral and long heads. The 9-10-11th-rib section was removed according to Hankins and Howe (1946) for compositional analysis. Each muscle was then wet-aged at 3.8 ± 2°C for 14 d in a cryovac B2570T bag (Sealed Air Corp., Duncan, SC) and then was frozen at −40°C. Steaks 2.54 cm thick were cut frozen from the anterior end of each muscle, with the exception of
the TEM and GRA, which were utilized whole due to size limitations for Warner-Bratzler shear force (WBSF) determination. The CIE L*, a*, and b* color scores were captured with a Minolta Chroma meter (Model CR310, Minolta Corp., Ramsey, NJ) 24 h postmortem to determine if objective lean color changes occurred due to treatment.
Ether Extraction and WarnerBratzler Shear Force Ether extraction was performed on the soft tissue of the 9-10-11th rib section to estimate compositional changes of the carcass. Ether extraction was performed on a sample of the LM to determine percent IMF of the LM. Steaks for WBSF determination were thawed for 18 h at 3.8 ± 2°C and then broiled on a Hamilton Beach HealthSmart 317.5 cm2 grill (Hamilton Beach- Proctor Silex Inc., Washington, NC) to an internal temperature of 70°C. The steaks were turned once at 35°C during cooking. Internal temperature was monitored using a copper–constantan thermocouple placed in the geometric center of the steak, which was attached to a temperature recorder. The steaks were then chilled for 18 h at 3.8 ± 2°C in preparation for WBSF core extraction. Six 1.27 cm cores were extracted from each steak parallel to the muscle fiber orientation. Each core was then sheared utilizing a WBSF device (crosshead speed = 200 mm/ min) attached to an Instron Universal Testing machine (Model 1011, Instron Corp., Canton, MA).
Statistical Analysis The study was designed as a randomized complete block design with individual animal as the experimental unit. Data was analyzed using PROC MIXED, Least Squares Means procedure of SAS (SAS Inst. Inc., Cary, NC) with a significance level of P < 0.05 and trends indicated with an equal sign. Random effects in the model included animal and muscle within animal. Fixed effects in the
635
model were treatment group and muscle within treatment group. There was a significant treatment × muscle interaction for WBSF; therefore, means will be presented by muscle across each treatment group for this variable.
RESULTS AND DISCUSSION Carcass Traits No differences (P > 0.05) were observed for HCW or dressing percent (Table 1). Kutzler et al. (2006) reported no differences in either HCW or BW between controls and RAC fed cull cows (200 mg/d per head), which agrees with this study. In contrast, Talton et al. (2006) reported RAC (200 mg/d per head) feeding tended to increase HCW in fed heifers; these findings suggest that mature animals may not be as responsive to a β-agonist compared with younger animals. Adjusted preliminary YG, a measure of subcutaneous fat deposition (Table 1), was similar (P > 0.05) across all treatment groups. Significant differences (P < 0.05) were observed for commodity weights in the clod, SMB, sirloin tip, and the top round, but when expressed on a percentage of HCW, no significant (P > 0.05) differences were observed (data not shown). Talton et al. (2006) reported similar results in RAC fed heifers. Feeding RAC did not (P > 0.05) alter the HCW percentages for any of the individual denuded muscles evaluated in this study. Ribeye area (REA; Table 1) was similar (P > 0.05) for all treatment groups. These findings agree with Holmer et al. (2006), but are in contrast with Schroeder et al., (2003b) who reported increased (P < 0.05) REA in steers and heifers fed 300 mg RAC/d per head. When REA is expressed per 100 kilograms of HCW (indicator of muscling), all treatment groups were similar (Table 1).
9-10-11th Rib Composition Differences (P < 0.05) were observed in percent fatfree lean of the
Dijkhuis et al.
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Table 1. Least squares means of cull cow carcass traits fed 4 graded levels of ractopamine-HCl (RAC) Treatment1 Item 2
HCW DP APYG3 REA4 REA, cm2/100 kg HCW5 Bone maturity6 Lean maturity7
CON
RAC 100
RAC 200
RAC 300
275.7 ± 6.20 53.8 ± 0.82 2.6 ± 0.06 27.9 ± 0.81 10.1 ± 0.24 572.8 ± 7.84 423.3 ± 15.13
258.1 ± 6.05 53.2 ± 0.80 2.5 ± 0.06 26.7 ± 0.79 10.3 ± 0.23 564.0 ± 7.66 437.7 ± 14.79
258.6 ± 6.05 51.6 ± 0.80 2.6 ± 0.06 25.9 ± 0.79 10.0 ± 0.23 578.8 ± 7.66 419.6 ± 14.79
268.0 ± 6.20 52.0 ± 0.81 2.7 ± 0.06 28.2 ± 0.81 10.4 ± 0.24 586.8 ± 7.84 407.6 ± 15.13
1
CON = cull cows fed control diet; RAC 100, RAC 200, RAC 300 = cull cows fed control diet plus 100, 200, or 300 mg RAC/d per head, respectively.
2
HCW = hot carcass weight, measured in kilograms.
3
APYG = adjusted preliminary YG.
4
REA = ribeye area measured in cm2.
5
REA in cm2/100 kg of HCW is used as an indicator of muscling.
6
Bone maturity: A = 100; B = 200; C = 300; D = 400; E = 500.
7
Lean maturity: A = 100; B = 200; C = 300; D = 400; E = 500.
9-10-11th rib section (Table 2), an indicator cut used to relate body composition changes between treatments. The RAC 300 treatment was 6.3% higher in fat-free lean compared with the CON treatment, and the RAC 100 and RAC 200 treatments were intermediate of the CON and RAC 300 treatments. With higher levels of RAC, lean accretion is generated at a faster rate than fat deposition. This would be expected considering RAC is a β-adrenergic agonist that redirects nutrients away from fat production and applies nutrients toward lean accretion (Eisemann et al., 1988; Miller et al., 1988; Mersmann, 1998).
Carcass Quality Percent IMF, marbling, color, texture, and firmness score was not significantly different (P > 0.05) among the treatment groups (Table 3). These results agreed with previous studies conducted on heifers (Schroeder et al., 2003b; Talton et al., 2006), with the exception of the Schroeder et al. (2003b) study which reported improvements (P < 0.06) in muscle color based on a subjective acceptability muscle color scale for heifers treated at all (100, 200, or 300 mg/d per head) RAC dose levels. The CIE L*, a*, and b* color scores (Table 3)
were not (P > 0.05) different when CON treatment was compared with RAC treatments.
Warner-Bratzler Shear Force Empirical data on WBSF reveals that RAC affects individual muscles (Table 4) rather than specific muscle groups such as muscles of locomotion or muscles of support. The INF, REF, SMB, and TRBlat all had significant (P < 0.05) differences for WBSF across treatment groups. WarnerBratzler shear force values for adductor, GRA, LM, TEM, TRBlong and vastus lateralis were not significantly
Table 2. Least squares means of the 9-10-11th rib composition from cull cows fed 4 graded levels of ractopamine-HCl (RAC) Treatment1 Item % Bone % Fat % FFL2 a,b
CON
RAC 100
RAC 200
RAC 300
18.8 ± 0.66 26.4 ± 1.87 54.8b ± 1.79
18.2 ± 0.66 22.4 ± 1.87 59.3ab ± 1.79
18.4 ± 0.73 24.4 ± 2.10 57.2ab ± 2.01
17.3 ± 0.66 21.6 ± 1.87 61.1a ± 1.79
Means in the same row having different superscripts differ (P < 0.05).
1
CON = cull cows fed control diet; RAC 100, RAC 200, RAC 300 = cull cows fed control diet plus 100, 200, or 300 mg RAC/d per head, respectively.
2
FFL = fat-free lean.
Ractopamine hydrochloride effect on cull cow composition
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Table 3. Least squares means of carcass quality traits: marbling, percent intramuscular fat, lean color, texture, firmness, and L*, a*, and b* color scores from the longissimus dorsi in between the 12th and 13th rib from cull cows fed 4 graded levels of ractopamine-HCl (RAC) Treatment1 Item 2
Marbling % IMF3 Color4 Texture5 Firmness6 L*, a*, b* color scores L*7 a*8 b*9
CON
RAC 100
RAC 200
RAC 300
261.9 ± 14.51 4.5 ± 0.55 4.6 ± 0.24 4.9 ± 0.23 3.5 ± 0.18
222.7 ± 14.18 3.5 ± 0.55 4.4 ± 0.24 4.6 ± 0.23 3.5 ± 0.17
246.4 ± 14.18 4.3 ± 0.61 4.6 ± 0.24 5.1 ± 0.23 3.0 ± 0.17
249.1 ± 14.51 4.4 ± 0.54 4.3 ± 0.24 5.0 ± 0.23 3.1 ± 0.18
40.3 ± 0.63 25.9 ± 0.38 10.4 ± 0.32
38.9 ± 0.63 24.9 ± 0.38 9.5 ± 0.32
38.6 ± 0.71 24.8 ± 0.42 9.5 ± 0.35
39.9 ± 0.63 24.9 ± 0.38 9.6 ± 0.32
1
CON = cull cows fed control diet; RAC 100, RAC 200, RAC 300 = cull cows fed control diet plus 100, 200, or 300 mg RAC/d per head, respectively.
2
Slightly abundant = 700; moderate = 600; modest = 500; small = 400; slight = 300; traces = 200; practically devoid = 100.
3
IMF = intramuscular fat.
4
Lean color: 1 = bright cherry red; 8 = extremely dark red.
5
Lean texture: 1 = very fine; 7 = extremely course.
6
Lean firmness: 1 = very firm; 7 = extremely soft.
7
Lightness/darkness: 0 = black; 100 = white.
8
a* value = green (−a), red (+a).
9
b* value = blue (−b), yellow (+b).
Table 4. Least squares means of Warner-Bratzler shear force values1 from cull cows fed 4 graded levels of ractopamine-HCl (RAC) Treatment3 Muscle2
CON
RAC 100
RAC 200
RAC 300
ADD GRA INF LM REF SMB TEM TRBlat TRBlong VAL
49.0 ± 3.24 40.2 ± 3.43 27.5b ± 3.24 37.3 ± 3.14 52.0ab ± 3.24 56.9a ± 3.24 46.1 ± 3.92 43.1ab ± 3.24 45.1 ± 3.24 53.9 ± 3.24
50.0 ± 1.77 36.3 ± 3.24 36.3a ± 3.33 44.1 ± 3.24 56.9a ± 3.33 46.1b ± 3.24 43.1 ± 3.24 50.0a ± 3.24 46.1 ± 3.24 52.0 ± 3.14
48.1 ± 3.92 35.3 ± 3.82 38.2a ± 3.82 45.1 ± 3.63 44.1b ± 3.92 50.0ab ± 3.92 45.1 ± 4.12 44.1ab ± 3.63 45.1 ± 3.63 53.0 ± 3.92
46.1 ± 3.43 38.2 ± 3.43 36.3a ± 3.33 44.1 ± 3.43 53.0ab ± 3.43 48.1ab ± 3.63 41.2 ± 3.63 39.2b ± 3.24 47.1 ± 3.43 55.9 ± 3.43
a,b 1
Means within rows with different superscripts differ at (P < 0.05).
Warner–Bratzler shear force measured in kilograms and converted to Newtons.
2
Muscle: adductor (ADD), gracilis (GRA), infraspinatus (INF), longissimus thoracicus (LM,), rectus femoris (REF), semimembranosus (SMB), teres major (TEM), triceps brachii lateral and long (TRBlat, TRBlong), and vastus lateralis (VAL).
3
CON = cull cows fed control diet; RAC 100, RAC 200, RAC 300 = cull cows fed control diet plus 100, 200, or 300 mg RAC/d per head, respectively.
Dijkhuis et al.
638 (P > 0.05) affected by RAC treatment. The INF decreased (P < 0.05) in tenderness with RAC treatment compared with CON. In contrast, with RAC supplementation the SMB was more (P < 0.05) tender for the RAC 100 treatment level compared with CON treatment. The REF and TRBlat experienced interactions between RAC treatments. The REF in the RAC 100 group had less (P < 0.05) tender WBSF values compared with the RAC 200 group, which had the most tender WBSF values of all treatment groups. The TRBlat was similar, indicating that the RAC 100 group produced less (P < 0.05) tender WBSF values in comparison to the RAC 300 group. Schroeder et al. (2003a) reported WBSF values increased in the LM from steers and heifers as RAC dosage increased. The data for the REF and TRBlat do not support the Schroeder et al. (2003a) findings. Shear values are independent of fat, which would eliminate cold shortening as a potential explanation. Possibly protein turnover diluted the existing crosslinked collagen content in the RAC 200 and RAC 300 treatment groups compared with the RAC 100, which would have more crosslinked collagen causing the RAC 100 treatment to be tougher in muscles of locomotion. Cranwell et al. (1996a,b) reported implanted fed cull cows with higher lean gains had more soluble collagen compared with control cows. Those findings do support those of the RAC 300 group due to the 6% increase in fat-free lean compared with the CON group; however, this is only speculation because the present study did not investigate collagen content.
IMPLICATIONS Feeding RAC at the 100, 200, or 300 mg/d per head to cull beef cows for the last 30 d on feed had little effect on carcass characteristics compared with CON treatment and had inconsistent effects on WBSF values, but RAC did increase total fat-free lean percentage. Because some of the results found from this study were
insignificant, it would not be advantageous for producers to feed RAC to cull cows at the levels and time period used in this study. However, the 6% increase of fat-free lean in the RAC 300 group would prove to be a plus for the packer producing lean trimmings intended for further processing.
LITERATURE CITED Bridge, K. Y., C. K. Smith II, and R. B. Young. 1998. Beta-adrenergic receptor gene expression in bovine skeletal muscle cells in culture. J. Anim. Sci. 76:2382. Cranwell, C. D., J. A. Unruh, J. R. Brethour, D. D. Simms, and R. E. Campbell. 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. Eisemann, J. H., G. B. Huntington, and C. L. Ferrell. 1988. Effects of dietary clenbuterol on metabolism of the hindquarters in steers. J. Anim. Sci. 66:342. Faulkner, D. B., F. K. McKeith, L. L. Berger, D. J. Kesler, and D. F. Parrett. 1989. Effects of testosterone propionate on performance and carcass characteristics of heifers and cows. J. Anim. Sci. 67:1907. Gonzalez, J. M., J. N. Carter, D. D. Johnson, S. E. Ouellette, and S. E. Johnson. 2007. Effect of ractopamine-hydrochloride and trenbolone acetate on longisssimus muscle fiber area, diameter, and satellite cell numbers in cull beef cows. J. Anim. Sci. 85:1893. Hankins, O. G., and P. F. Howe. 1946. Estimation of the composition of beef carcasses and cuts. USDA Tech. Bull. No. 926. USDA, Washington, D. C. Holmer, S. F., J. Holmer, L. L. Berger, M. S. Brewer, F. K. McKeith, and J. Killefer. 2006. Effects of feeding regimen and enhancement on live performance, carcass characteristics, and meat quality in beef cull cows. p. 49 in Proc. 59th Reciprocal Meats Conference, Champaign-Urbana, IL. Jurie, C., B. Picard, J. F. Hocquette, E. Dransfield, D. Micol, and A. Listrat. 2007. Muscle and meat quality characteristics of Holstein and Salers cull cows. Meat Sci. 77:459. Kutzler, L. W., S. F. Holmer, C. M. Leick, F. K. McKeith, and J. Killefer. 2006. Effects of feeding regimens on animal growth, longissimus muscle DNA and protein concentration and gene expression in beef cull cows. p. 30
in Proc. 59th Reciprocal Meats Conference, Champaign-Urbana, IL. 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. Mersmann, H. J. 1998. Overview of the effects of β-adrenergic receptor agonists on animal growth including mechanisms of action. J. Anim. Sci. 76:160. 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. Miller, M. F., D. K. Garcia, M. E. Coleman, P. A. Ekeren, D. K. Lunt, K. A. Wagner, M. Procknor, T. H. Welsh Jr, and S. B. Smith. 1988. Adipose tissue, longissimus muscle and anterior pituitary growth and function in clenbuterol-fed heifers. J. Anim. Sci. 66:12. 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. Schnell, T. D., K. E. Belk, J. D. Tatum, R. K. Miller, and G. C. Smith. 1997. Performance, carcass, and palatability traits for cull cows fed high-energy concentrate diets for 0, 14, 28, 42, or 56 Days. J. Anim. Sci. 75:1195. Schroeder, A. L., D. M. Polser, S. B. Laudert, and G. J. Vogel. 2003a. Effects of optaflexx on sensory properties of beef trial summary. Elanco Animal Health, Greenfield, IN. Schroeder, A. L., D. M. Polser, S. B. Laudert, G. J. Vogel, T. Ripberger, and M. T. Van Koevering. 2003b. Effect of optaflexx on growth performance and carcass traits of steers and heifers trial summary. Elanco Animal Health, Greenfield, IN. Stelzleni, A. M., L. E. Patten, D. D. Johnson, C. R. Calkins, and B. L. Gwartney. 2007. Benchmarking carcass characteristics and muscles from commercially identified beef and dairy cull cow carcasses for Warner-Bratzler shear force and sensory attributes. J. Anim. Sci. 85:2631. Talton, C. S., T. D. Pringle, G. M. Hill, C. R. Kerth, J. N. Shook, and M. E. Pence. 2006. Effects of ractopamine hydrochloride and ovariectomy on animal performance, carcass traits, and yields of carcass subprimals and value cuts in feedlot heifers. p. 34 in Proc. 59th Reciprocal Meats Conference, Champaign-Urbana, IL. Wooten, R. A., C. B. Roubicek, J. A. Marchello, F. D. Dryden, and R. S. Swingle. 1979. Realimentation of cull range cows. 2. Changes in carcass traits. J. Anim. Sci. 48:823.
C Ractopamine S : Feeding Hydrochloride to ase
tudy
Cull Cows: Effects on Carcass Composition, Warner-Bratzler Shear Force, and Yield R. D. Dijkhuis,*1 D. D. Johnson,* and J. N. Carter† *Department of Animal Sciences, University of Florida, Gainesville, 32611; and †North Florida Research and Education Center, University of Florida, Marianna 32446
ABSTRACT Culled beef cows (n = 95, 10.5 ± 1.2 yr), were randomly sorted into 1 of 4 pens based on level of ractopamine (RAC) supplementation including control (no RAC), 100, 200, or 300 mg/d of RAC for the final 30 d of a 48-d feeding period. At 24 h postmortem, carcass data were collected, carcasses were fabricated, and 9 muscles (adductor, gracilis, infraspinatus, longissimus thoracicus, rectus femoris, semimembranosus, teres major, triceps brachii, and vastus lateralis) were removed. The triceps brachii was further separated into the long and lateral heads. Feeding RAC had little effect on carcass characteristics or Warner-Bratzler shear force (P > 0.05) at any treatment level. Percentage of fatfree lean increased (P < 0.05) for RAC at 300 mg when compared with controlfed. Overall, feeding RAC had little to no effect on carcass characteristics. This study shows that producers feeding RAC to cull cows will not directly benefit from increased carcass performance compared with cull cows not supplemented with
1
Corresponding author: [email protected]
RAC. In contrast, packers will indirectly benefit from cull cows being fed RAC at 300 mg/d per head for the final 30 d of a 48-d feeding period due to the increase in percent fat-free lean. Key words: carcass composition, cull cows, ractopamine, Warner-Bratzler shear force, yield
INTRODUCTION Cull cows, a byproduct of the beef cow-calf industry, can represent 10 to 20% of a producer’s income (Sawyer et al., 2004). Often times cull cows are marketed due to health or structural related problems or because they did not conceive. Cull cows are typically marketed when they are in poor body condition, resulting in less than optimal revenues at sale. Previous research has shown that feeding cull cows a concentrate diet will increase hot carcass weights (HCW), longissimus muscle area, intramuscular fat (IMF), subcutaneous fat, and fat-free soft tissue (Wooten et al., 1979; Matulis et al., 1987; Miller et al., 1987; Faulkner et al., 1989; Cranwell et al., 1996b; Schnell
et al., 1997; Gonzalez et al., 2007; Jurie et al., 2007; Stelzleni et al., 2007). Supplementation with a type I β-adrenergic receptor agonist (ractopamine-HCl; RAC) increases protein accretion 25 to 30% at the expense of fat storage (Mersmann, 1998; Bridge et al., 1998). Also, Eisemann et al. (1988) reported that dosage level and dose duration of β agonists can influence receptor expression. The objective of this study was to determine whether feeding increased dietary levels of RAC for 30 d will increase lean accretion and decrease fat accretion, therefore increasing total lean yields of cull cows.
MATERIALS AND METHODS Experimental Animals Two truckloads (n = 48 each; 10.5 ± 1.2 yr) of cull crossbred cows (predominately Beefmaster and Brangus) were transported from a commercial cow-calf operation in south Florida (Okeechobee, FL) to a designated feeding facility in Williston, FL. Upon arrival, cows were weighed and treated with a pour-on endectocide (Decto-
Ractopamine hydrochloride effect on cull cow composition
max Pfizer Inc., New York, NY). Cull cows were randomly assigned to 1 of 4 treatments for the final 30 d of feeding consisting of control (CON; no supplemental RAC), RAC 100 (100 mg RAC/d per head), RAC 200 (200 mg RAC/d per head), and RAC 300 (300 mg RAC/d per head). Each treatment group was penned and fed together ad libitum from a self-feeder for a total of 48 d including RAC supplementation. The basal diet was comprised of the following ingredients: soybean hulls, citrus pulp, cracked corn, wheat middlings, cottonseed hulls, cottonseed meal, molasses, tallow, and urea. The diet contained approximately 87.6% DM, 14% CP (DM basis), and 79.5% TDN. On d 49, cows were transported to a commercial slaughter facility (Central Packing, Center Hill, FL) and harvested in a conventional manner.
Muscle Sample Preparation and CIE (Comission Internationale de l’Eclairage) L*, a*, and b* Color At 24 h postmortem, carcasses were fabricated and 9 muscles [adductor; gracilis (GRA); infraspinatus (INF); longissimus thoracicus (LM); rectus femoris (REF); semimembranosus (SMB); teres major (TEM); triceps brachii, lateral and long heads (TRB, TRBlat and TRBlong); and vastus lateralis] were removed and transported to the University of Florida’s Meat Processing Center (Gainesville, FL). Commodity (0.64 cm fat trim level) weights were recorded from the selected muscles, which were then trimmed to a zero (0.0 cm) fat level to determine denuded weights. During the denuding process, the TRB was further separated in lateral and long heads. The 9-10-11th-rib section was removed according to Hankins and Howe (1946) for compositional analysis. Each muscle was then wet-aged at 3.8 ± 2°C for 14 d in a cryovac B2570T bag (Sealed Air Corp., Duncan, SC) and then was frozen at −40°C. Steaks 2.54 cm thick were cut frozen from the anterior end of each muscle, with the exception of
the TEM and GRA, which were utilized whole due to size limitations for Warner-Bratzler shear force (WBSF) determination. The CIE L*, a*, and b* color scores were captured with a Minolta Chroma meter (Model CR310, Minolta Corp., Ramsey, NJ) 24 h postmortem to determine if objective lean color changes occurred due to treatment.
Ether Extraction and WarnerBratzler Shear Force Ether extraction was performed on the soft tissue of the 9-10-11th rib section to estimate compositional changes of the carcass. Ether extraction was performed on a sample of the LM to determine percent IMF of the LM. Steaks for WBSF determination were thawed for 18 h at 3.8 ± 2°C and then broiled on a Hamilton Beach HealthSmart 317.5 cm2 grill (Hamilton Beach- Proctor Silex Inc., Washington, NC) to an internal temperature of 70°C. The steaks were turned once at 35°C during cooking. Internal temperature was monitored using a copper–constantan thermocouple placed in the geometric center of the steak, which was attached to a temperature recorder. The steaks were then chilled for 18 h at 3.8 ± 2°C in preparation for WBSF core extraction. Six 1.27 cm cores were extracted from each steak parallel to the muscle fiber orientation. Each core was then sheared utilizing a WBSF device (crosshead speed = 200 mm/ min) attached to an Instron Universal Testing machine (Model 1011, Instron Corp., Canton, MA).
Statistical Analysis The study was designed as a randomized complete block design with individual animal as the experimental unit. Data was analyzed using PROC MIXED, Least Squares Means procedure of SAS (SAS Inst. Inc., Cary, NC) with a significance level of P < 0.05 and trends indicated with an equal sign. Random effects in the model included animal and muscle within animal. Fixed effects in the
635
model were treatment group and muscle within treatment group. There was a significant treatment × muscle interaction for WBSF; therefore, means will be presented by muscle across each treatment group for this variable.
RESULTS AND DISCUSSION Carcass Traits No differences (P > 0.05) were observed for HCW or dressing percent (Table 1). Kutzler et al. (2006) reported no differences in either HCW or BW between controls and RAC fed cull cows (200 mg/d per head), which agrees with this study. In contrast, Talton et al. (2006) reported RAC (200 mg/d per head) feeding tended to increase HCW in fed heifers; these findings suggest that mature animals may not be as responsive to a β-agonist compared with younger animals. Adjusted preliminary YG, a measure of subcutaneous fat deposition (Table 1), was similar (P > 0.05) across all treatment groups. Significant differences (P < 0.05) were observed for commodity weights in the clod, SMB, sirloin tip, and the top round, but when expressed on a percentage of HCW, no significant (P > 0.05) differences were observed (data not shown). Talton et al. (2006) reported similar results in RAC fed heifers. Feeding RAC did not (P > 0.05) alter the HCW percentages for any of the individual denuded muscles evaluated in this study. Ribeye area (REA; Table 1) was similar (P > 0.05) for all treatment groups. These findings agree with Holmer et al. (2006), but are in contrast with Schroeder et al., (2003b) who reported increased (P < 0.05) REA in steers and heifers fed 300 mg RAC/d per head. When REA is expressed per 100 kilograms of HCW (indicator of muscling), all treatment groups were similar (Table 1).
9-10-11th Rib Composition Differences (P < 0.05) were observed in percent fatfree lean of the
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Table 1. Least squares means of cull cow carcass traits fed 4 graded levels of ractopamine-HCl (RAC) Treatment1 Item 2
HCW DP APYG3 REA4 REA, cm2/100 kg HCW5 Bone maturity6 Lean maturity7
CON
RAC 100
RAC 200
RAC 300
275.7 ± 6.20 53.8 ± 0.82 2.6 ± 0.06 27.9 ± 0.81 10.1 ± 0.24 572.8 ± 7.84 423.3 ± 15.13
258.1 ± 6.05 53.2 ± 0.80 2.5 ± 0.06 26.7 ± 0.79 10.3 ± 0.23 564.0 ± 7.66 437.7 ± 14.79
258.6 ± 6.05 51.6 ± 0.80 2.6 ± 0.06 25.9 ± 0.79 10.0 ± 0.23 578.8 ± 7.66 419.6 ± 14.79
268.0 ± 6.20 52.0 ± 0.81 2.7 ± 0.06 28.2 ± 0.81 10.4 ± 0.24 586.8 ± 7.84 407.6 ± 15.13
1
CON = cull cows fed control diet; RAC 100, RAC 200, RAC 300 = cull cows fed control diet plus 100, 200, or 300 mg RAC/d per head, respectively.
2
HCW = hot carcass weight, measured in kilograms.
3
APYG = adjusted preliminary YG.
4
REA = ribeye area measured in cm2.
5
REA in cm2/100 kg of HCW is used as an indicator of muscling.
6
Bone maturity: A = 100; B = 200; C = 300; D = 400; E = 500.
7
Lean maturity: A = 100; B = 200; C = 300; D = 400; E = 500.
9-10-11th rib section (Table 2), an indicator cut used to relate body composition changes between treatments. The RAC 300 treatment was 6.3% higher in fat-free lean compared with the CON treatment, and the RAC 100 and RAC 200 treatments were intermediate of the CON and RAC 300 treatments. With higher levels of RAC, lean accretion is generated at a faster rate than fat deposition. This would be expected considering RAC is a β-adrenergic agonist that redirects nutrients away from fat production and applies nutrients toward lean accretion (Eisemann et al., 1988; Miller et al., 1988; Mersmann, 1998).
Carcass Quality Percent IMF, marbling, color, texture, and firmness score was not significantly different (P > 0.05) among the treatment groups (Table 3). These results agreed with previous studies conducted on heifers (Schroeder et al., 2003b; Talton et al., 2006), with the exception of the Schroeder et al. (2003b) study which reported improvements (P < 0.06) in muscle color based on a subjective acceptability muscle color scale for heifers treated at all (100, 200, or 300 mg/d per head) RAC dose levels. The CIE L*, a*, and b* color scores (Table 3)
were not (P > 0.05) different when CON treatment was compared with RAC treatments.
Warner-Bratzler Shear Force Empirical data on WBSF reveals that RAC affects individual muscles (Table 4) rather than specific muscle groups such as muscles of locomotion or muscles of support. The INF, REF, SMB, and TRBlat all had significant (P < 0.05) differences for WBSF across treatment groups. WarnerBratzler shear force values for adductor, GRA, LM, TEM, TRBlong and vastus lateralis were not significantly
Table 2. Least squares means of the 9-10-11th rib composition from cull cows fed 4 graded levels of ractopamine-HCl (RAC) Treatment1 Item % Bone % Fat % FFL2 a,b
CON
RAC 100
RAC 200
RAC 300
18.8 ± 0.66 26.4 ± 1.87 54.8b ± 1.79
18.2 ± 0.66 22.4 ± 1.87 59.3ab ± 1.79
18.4 ± 0.73 24.4 ± 2.10 57.2ab ± 2.01
17.3 ± 0.66 21.6 ± 1.87 61.1a ± 1.79
Means in the same row having different superscripts differ (P < 0.05).
1
CON = cull cows fed control diet; RAC 100, RAC 200, RAC 300 = cull cows fed control diet plus 100, 200, or 300 mg RAC/d per head, respectively.
2
FFL = fat-free lean.
Ractopamine hydrochloride effect on cull cow composition
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Table 3. Least squares means of carcass quality traits: marbling, percent intramuscular fat, lean color, texture, firmness, and L*, a*, and b* color scores from the longissimus dorsi in between the 12th and 13th rib from cull cows fed 4 graded levels of ractopamine-HCl (RAC) Treatment1 Item 2
Marbling % IMF3 Color4 Texture5 Firmness6 L*, a*, b* color scores L*7 a*8 b*9
CON
RAC 100
RAC 200
RAC 300
261.9 ± 14.51 4.5 ± 0.55 4.6 ± 0.24 4.9 ± 0.23 3.5 ± 0.18
222.7 ± 14.18 3.5 ± 0.55 4.4 ± 0.24 4.6 ± 0.23 3.5 ± 0.17
246.4 ± 14.18 4.3 ± 0.61 4.6 ± 0.24 5.1 ± 0.23 3.0 ± 0.17
249.1 ± 14.51 4.4 ± 0.54 4.3 ± 0.24 5.0 ± 0.23 3.1 ± 0.18
40.3 ± 0.63 25.9 ± 0.38 10.4 ± 0.32
38.9 ± 0.63 24.9 ± 0.38 9.5 ± 0.32
38.6 ± 0.71 24.8 ± 0.42 9.5 ± 0.35
39.9 ± 0.63 24.9 ± 0.38 9.6 ± 0.32
1
CON = cull cows fed control diet; RAC 100, RAC 200, RAC 300 = cull cows fed control diet plus 100, 200, or 300 mg RAC/d per head, respectively.
2
Slightly abundant = 700; moderate = 600; modest = 500; small = 400; slight = 300; traces = 200; practically devoid = 100.
3
IMF = intramuscular fat.
4
Lean color: 1 = bright cherry red; 8 = extremely dark red.
5
Lean texture: 1 = very fine; 7 = extremely course.
6
Lean firmness: 1 = very firm; 7 = extremely soft.
7
Lightness/darkness: 0 = black; 100 = white.
8
a* value = green (−a), red (+a).
9
b* value = blue (−b), yellow (+b).
Table 4. Least squares means of Warner-Bratzler shear force values1 from cull cows fed 4 graded levels of ractopamine-HCl (RAC) Treatment3 Muscle2
CON
RAC 100
RAC 200
RAC 300
ADD GRA INF LM REF SMB TEM TRBlat TRBlong VAL
49.0 ± 3.24 40.2 ± 3.43 27.5b ± 3.24 37.3 ± 3.14 52.0ab ± 3.24 56.9a ± 3.24 46.1 ± 3.92 43.1ab ± 3.24 45.1 ± 3.24 53.9 ± 3.24
50.0 ± 1.77 36.3 ± 3.24 36.3a ± 3.33 44.1 ± 3.24 56.9a ± 3.33 46.1b ± 3.24 43.1 ± 3.24 50.0a ± 3.24 46.1 ± 3.24 52.0 ± 3.14
48.1 ± 3.92 35.3 ± 3.82 38.2a ± 3.82 45.1 ± 3.63 44.1b ± 3.92 50.0ab ± 3.92 45.1 ± 4.12 44.1ab ± 3.63 45.1 ± 3.63 53.0 ± 3.92
46.1 ± 3.43 38.2 ± 3.43 36.3a ± 3.33 44.1 ± 3.43 53.0ab ± 3.43 48.1ab ± 3.63 41.2 ± 3.63 39.2b ± 3.24 47.1 ± 3.43 55.9 ± 3.43
a,b 1
Means within rows with different superscripts differ at (P < 0.05).
Warner–Bratzler shear force measured in kilograms and converted to Newtons.
2
Muscle: adductor (ADD), gracilis (GRA), infraspinatus (INF), longissimus thoracicus (LM,), rectus femoris (REF), semimembranosus (SMB), teres major (TEM), triceps brachii lateral and long (TRBlat, TRBlong), and vastus lateralis (VAL).
3
CON = cull cows fed control diet; RAC 100, RAC 200, RAC 300 = cull cows fed control diet plus 100, 200, or 300 mg RAC/d per head, respectively.
Dijkhuis et al.
638 (P > 0.05) affected by RAC treatment. The INF decreased (P < 0.05) in tenderness with RAC treatment compared with CON. In contrast, with RAC supplementation the SMB was more (P < 0.05) tender for the RAC 100 treatment level compared with CON treatment. The REF and TRBlat experienced interactions between RAC treatments. The REF in the RAC 100 group had less (P < 0.05) tender WBSF values compared with the RAC 200 group, which had the most tender WBSF values of all treatment groups. The TRBlat was similar, indicating that the RAC 100 group produced less (P < 0.05) tender WBSF values in comparison to the RAC 300 group. Schroeder et al. (2003a) reported WBSF values increased in the LM from steers and heifers as RAC dosage increased. The data for the REF and TRBlat do not support the Schroeder et al. (2003a) findings. Shear values are independent of fat, which would eliminate cold shortening as a potential explanation. Possibly protein turnover diluted the existing crosslinked collagen content in the RAC 200 and RAC 300 treatment groups compared with the RAC 100, which would have more crosslinked collagen causing the RAC 100 treatment to be tougher in muscles of locomotion. Cranwell et al. (1996a,b) reported implanted fed cull cows with higher lean gains had more soluble collagen compared with control cows. Those findings do support those of the RAC 300 group due to the 6% increase in fat-free lean compared with the CON group; however, this is only speculation because the present study did not investigate collagen content.
IMPLICATIONS Feeding RAC at the 100, 200, or 300 mg/d per head to cull beef cows for the last 30 d on feed had little effect on carcass characteristics compared with CON treatment and had inconsistent effects on WBSF values, but RAC did increase total fat-free lean percentage. Because some of the results found from this study were
insignificant, it would not be advantageous for producers to feed RAC to cull cows at the levels and time period used in this study. However, the 6% increase of fat-free lean in the RAC 300 group would prove to be a plus for the packer producing lean trimmings intended for further processing.
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