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ANIMAL PRODUCTS |
,1
* Balanced Life Nutrition, Canyon, TX 79015;
and
Intervet Inc., a part of Schering-Plough Corporation, Millsboro, DE 19966;
and
Department of Animal Science, Oklahoma State University, Stillwater 74078; and
Department of Animal and Food Science, Texas Tech University, Lubbock 79409
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Abstract |
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 Top Abstract INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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Key Words: β-adrenergic agonist • beef cattle • carcass composition • tenderness • zilpaterol hydrochloride
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INTRODUCTION |
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TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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; Moloney et al., 1990; Chikhou et al., 1993), very little has been reported on zilpaterol hydrochloride effects on cutability and as a repartitioning agent. Plascencia et al. (1999) and Hilton et al. (2009) are the only studies available that have reported that zilpaterol hydrochloride increased beef carcass cutability of boneless closely trimmed primal and retail cuts.
As with any repartitioning agent, there is a concern of treatment effects on meat shear force and palatability. Other βAA such as clenbuterol, L-644,969, and cimaterol have been shown to have negative effects on beef shear force (Miller et al., 1988; Boucqué et al., 1994; Moloney et al., 1994). Even the β1-agonist ractopamine hydrochloride has been shown to increase beef LM Warner-Bratzler shear force and decrease sensory tenderness scores when supplemented at approximately 300 mg/animal per day (Schroeder et al., 2003a). Studies conducted with zilpaterol hydrochloride in cattle have shown increased beef LM shear force and decreased sensory tenderness scores, whereas effects on semitendinosus shear force and tenderness are much more variable (Strydom et al., 1998; Strydom and Nel, 1999; Hilton et al., 2009).
Because previous reports of zilpaterol hydrochloride are limited, the objective of these experiments was to increase information available about zilpaterol hydrochloride and to report on treatment effects on carcass composition and meat palatability. The studies were conducted on carcasses supplied by the studies reported by Montgomery et al. (2009).
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MATERIALS AND METHODS |
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TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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). Cattle
Experiments were conducted using 480 steers and 480 heifers at 3 study locations (Reedley, CA; Parma, ID; and Canyon, TX) as described by Montgomery et al. (2009). For each study location 160 steers and 160 heifers were selected primarily by BW and condition from a larger population of cattle for the experiments (cattle were predominantly English cross and Continental cross types of cattle). Cattle were stratified within sex by initial BW (study d -1) and assigned randomly within BW stratum to 1 of the 4 treatments in a randomized complete block design (4 blocks/treatment for each sex). The 4 treatments were arranged in a 2 (no zilpaterol vs. zilpaterol; 8.3 mg/kg, DM basis) x 2 (20- or 40-d duration of zilpaterol feeding) factorial. Animals were sorted to a newly assigned dirt floor pen (d 1 of the experiment), and each pen consisted of 10 animals. After treatments were complete, all cattle received a withdrawal basal diet for 5 consecutive days. At each site cattle were administered the zilpaterol or no zilpaterol treatments in a manner so that all cattle were slaughtered on the same day.
Slaughter
Differences in the slaughter process at each of the sites is explained by Montgomery et al. (2009). At slaughter, HCW was collected. For each set of control and zilpaterol treatment pens within a BW block (n = 20 carcasses) the HCW data were used to calculate a mean HCW. There were 16 mean HCW calculated per site. For selection purposes, a carcass weight selection window was calculated for each set of treatment and control pens by adding and subtracting 13.6 kg to the respective mean HCW. Because zilpaterol has been shown to increase BW and carcass weight, a carcass selection window was used to minimize the effect of zilpaterol treatment on carcass weight and the potential for autocorrelation of composition factors with carcass weight. After chilling, carcasses were ribbed at the 12th rib, and quality and yield grade traits were recorded (USDA, 1997). For each pen 2 carcasses were randomly selected from carcasses within the carcass weight selection window that graded USDA Select or low Choice. For each pen the 2 selected carcasses were railed off and separated from remaining carcasses. For each selected carcass the right carcass side was divided into the hindquarter and forequarter and each quarter was wrapped in plastic to reduce moisture evaporation and contamination. The other carcass side (left side) was fabricated at the slaughter facility and the strip loin [Institutional Meat Purchase Specifications (IMPS) #180] was collected. For each study site the selected right carcass side quarters and strip loins were shipped (0 to 9°C) together to the Texas Tech Meat Laboratory (Lubbock) and stored at 4°C until dissection.
Carcass Dissection
Because treatments were arranged in a 2 x 2 factorial, there were 4 different treatments within a BW block for steers and heifers at each site, with a total of 32 pens per site. For dissection a total of 8 carcasses consisting of the 4 different treatments from the same BW block for both steers and heifers were dissected for 8 consecutive days. There were 64 right carcass sides dissected for each of the 3 sites. Each carcass side was divided into the wholesale beef primals consisting of the chuck, rib, loin, and round. All soft tissue was dissected from the bone and cut into 5 cm3 cubes. The dissected tissue and bone for each carcass was weighed. Bone weight included bones, cartilage and heavy tendons, connective tissue, and elastin. All the tissue from one carcass side was placed into a large mixer/grinder (model 4200, Holymatic, Countryside, IL) and mixed for 5 min. After mixing, the soft tissue was coarse ground through a 1.3-cm plate. Next, the coarse-ground soft tissue was placed back in the mixer/grinder and mixed to homogeneity for 5 min. The mixed coarse-ground soft tissue then was fine ground through a 0.3-cm plate. From this fine-ground homogeneous tissue sample, an approximate 2.27-kg subsample was taken and subsampled further to approximately 200 g. The 200-g soft tissue sample was frozen in liquid N and homogenized to a fine powder in a 0.24-L Waring blender jar (model 4937, Sunbeam Products, Boca Raton, FL). The powdered homogeneous tissue samples were then stored at –80°C until analysis.
Chemical Analysis
Soft tissue moisture, protein, fat, and ash were determined in quadruplicate according to AOAC (1990; methods 992.15, 991.36, 920.153, and oven-drying methods, for CP, crude fat, ash, and moisture, respectively) techniques for each carcass selected. Tissue moisture was determined in quadruplicate using an approximate 4-g sample and drying samples at 100°C for at least 16 h in a drying oven. Tissue protein was determined in quadruplicate on approximately 0.7-g samples using a Leco protein analyzer (model FP-2000-602-600-400, Leco Corp., St. Joseph, MI). Tissue fat was determined in quadruplicate using an approximate 4-g sample using ether extraction. Tissue ash was determined in quadruplicate by placing an approximate 5-g sample in a crucible and drying at 100°C for at least 16 h. Samples were then ashed in a muffle furnace (model 5550-126 Isotemp muffle furnace, Fisher Scientific, Houston, TX) at 550°C for 1 h, and then cooled to room temperature. Samples were weighed before and after ashing. Carcass moisture, fat, protein, and ash weights were calculated by multiplying the respective soft tissue percentage by the soft tissue weight per animal.
Carcass moisture, fat, protein and ash percentages were calculated by dividing the respective soft tissue weights by the side weight and multiplying by 100. Carcass bone percentage was calculated by dividing the carcass bone weight by the carcass side weight and multiplying by 100. Protein to fat ratios were calculated by dividing carcass percentage protein by carcass percentage fat. Protein to bone ratios were calculated by dividing carcass percentage protein by carcass percentage bone.
Shear Force and Sensory Analysis
Upon receipt at the Texas Tech Meat Laboratory, each strip loin was stored at 4°C until 28 d postmortem. At 28 d postmortem the strip loins were frozen at –20°C. Each frozen strip loin was cut into 2.54-cm-thick steaks, placed in Cryovac B160 beef bags (Cryovac, Duncan, SC), and stored frozen until Warner-Bratzler shear force (WBSF) determination. Sensory evaluations were performed on steaks collected from the Idaho site only. Sensory panel evaluations and WBSF determinations were conducted according to American Meat Science Association guidelines (AMSA, 1995). Steaks for sensory and WBSF determinations were thawed slowly in a 2°C cooler for 18 to 24 h, and cooked on a MagiGrill belt grill (model TBG-60 electric conveyor grill, MagiKitch’n, Quakertown, PA) for 5 min and 40 s with a grill-plate thickness of 2.16 cm and grill-plate temperature of 163°C to an internal steak temperature of 71°C. Individual steaks were weighed before and after cooking to determine cooking loss on WBSF steaks.
Once cooked, steaks for WBSF evaluation were placed on plastic trays, covered with polyvinyl chloride film, and chilled for 18 to 24 h at 2°C. Six round 1.27-cm-diameter cores were removed from each LM steak parallel to the muscle fiber orientation, and sheared once with a WBSF instrument (GR Elec. Mfg. Co., Manhattan, KS). The multiple shear force determinations for each steak were then averaged for statistical analysis.
Sensory steaks were cut into 1-cm3 cubes immediately after cooking and stored in warming pans (approximately 5 min) until served (at approximately 50°C) to the trained sensory panel (AMSA, 1995). Samples were evaluated by a 6- to 8-member panel trained according to the standards of Cross et al. (1978). Steaks were evaluated for overall juiciness, overall tenderness, flavor intensity, beef flavor (8 = extremely juicy, tender, intense, characteristic beef flavor; 1 = extremely dry, tough, bland, uncharacteristic beef flavor), as well as off flavor (5 = extremely off flavor; 1 = no off flavor).
Calculations and Statistical Analyses
Empty BW, empty body fat, and final shrunk BW adjusted to 28% empty body fat were calculated as described by Guiroy et al. (2002) using the carcass measurements of the current study carcasses. Carcass measurements are presented in Montgomery et al. (2009).
Empty BW, empty body fat, adjusted final shrunk BW, carcass composition, LM cooking loss, LM WBSF, and sensory traits were analyzed using a 2 (no zilpaterol vs. zilpaterol) x 2 (20- or 40-d duration of zilpaterol feeding) factorial arrangement of treatments in a randomized complete block design, where pen was the experimental unit. Data for steers and heifers were analyzed separately. Data were pooled across all experimental sites for statistical analysis. For the pooled analysis the ANOVA was performed using the MIXED procedure (SAS Inst. Inc., Cary, NC). Heterogeneity among experiment locations was tested using a residual and random component. Because no experiment heterogeneity was observed, an unweighted mixed model analysis was conducted for all response variables. The model included yijklm = µ + Li + Dj + Tk + Bl(Li) + (LD)ij + (LT)ik + (DT)jk + (LDT)ijk + eijkl, where y is the observed value, µ the total mean, L the random effect of location, D the fixed effect of treatment duration, T the fixed effect of zilpaterol treatment, B(L) the random effect of block within location, and e is the residual variation. Predicted empty body fat was regressed on observed empty body fat using the GLM procedure of SAS.
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RESULTS |
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TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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Steers.
There were no zilpaterol x duration of zilpaterol feeding interactions (P 
0.14) for compositional data in steers (Table 1). Side weight, soft tissue weight, and bone weight were not affected (P 0.17) by feeding zilpaterol hydrochloride, most likely because of the specific selection criteria used to select the carcasses for these experiments. Feeding zilpaterol hydrochloride increased (P 
0.02) soft tissue protein percentage and weight, carcass protein percentage, and protein to bone ratio of steers. In addition, carcass ash percentage tended (P = 0.07) to be greater when zilpaterol was fed to steers. Percentage soft tissue moisture, fat, and ash were not affected (P 0.10) by zilpaterol feeding of steers, and soft tissue fat weight was not affected (P = 0.37) by the zilpaterol treatment. Carcass moisture and fat percentage were not affected (P 0.11) by the zilpaterol treatment, and zilpaterol feeding did not influence (P 0.14) carcass bone percentage or protein to fat ratio of steers.
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0.15) bone weight, soft tissue moisture, fat or protein percentages, soft tissue fat weight, carcass moisture, fat, or protein percentages, carcass bone percentage, protein:fat ratio, or protein:bone ratio of steers.
Heifers.
There were no zilpaterol x duration of zilpaterol feeding interactions (P 0.47) for compositional data in heifers (Table 2). Feeding zilpaterol hydrochloride increased (P 0.01) the carcass side weight and soft tissue weight of heifers, whereas bone weight was not affected (P = 0.24) by zilpaterol. Soft tissue protein percentage was increased (P = 0.01) for heifers fed zilpaterol, although soft tissue ash percentage was not affected (P = 0.66). The zilpaterol treatment tended (P = 0.10) to increase soft tissue moisture percentage and tended to decrease (P = 0.08) soft tissue fat percentage. Feeding zilpaterol hydrochloride increased (P 0.004) soft tissue moisture and soft tissue protein weights. However, soft tissue fat and ash weights were not influenced (P 0.23) by zilpaterol treatment of heifers. Carcass percentage moisture and protein were increased (P 0.04) in heifers fed zilpaterol, whereas carcass percentage bone was decreased (P = 0.02). Carcass percentage fat and ash were not influenced (P 0.12) by zilpaterol treatment. Protein:moisture and protein:bone ratios were increased (P 0.01) in heifers fed zilpaterol, whereas protein:fat ratio tended (P = 0.10) to be increased by the zilpaterol treatment.
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0.12) by duration of feeding. Empty Body Fat
Steers.
There were no zilpaterol x duration of zilpaterol feeding interactions (P 0.53) for empty body fat or 28% adjusted final BW data in steers (Table 3). Empty BW was not affected (P = 0.17) by feeding zilpaterol hydrochloride. However, calculated percentage empty body fat and 28% adjusted final BW responded with a zilpaterol main effect (P 0.05). Feeding steers zilpaterol decreased calculated percentage empty body fat and increased 28% adjusted final BW. Averaged across duration, zilpaterol decreased (P = 0.02) empty body fat by 0.95 percentage units and increased (P = 0.05) 28% adjusted final BW by 28.5 kg compared with no zilpaterol. When compared over the different quality grades of the carcasses, zilpaterol did not affect (P 0.05) observed or predicted empty body fat percentage of steer carcasses (Table 4); however, the selection of only Select and low Choice carcasses for the study probably affected these findings. The effect of zilpaterol hydrochloride on the relationship between observed and predicted empty body fat percentage was tested using all the steer and heifer carcasses. The regression equation was y = –9.79 ± 2.56 + 1.35 ± 0.09x (R2 = 0.55; root mean square error = 3.00) for the relationship between observed and predicted empty body fat percentage (Figure 1). The same relationship for steers only was tested (Figure 2). The regression equation for control steers (line a) was y = –21.98 ± 4.49 + 1.74 ± 0.17x (R2 = 0.69; root mean square error = 2.88). The regression equation for steers fed zilpaterol hydrochloride (line b) was y = –1.47 ± 4.91 + 1.02 ± 0.18x (R2 = 0.43; root mean square error = 2.53).
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0.44) for empty body fat or 28% adjusted final BW data in heifers (Table 3
). Calculated empty body percentage and BW were not affected (P 0.13) by feeding zilpaterol hydrochloride. However, 28% adjusted final BW responded with a zilpaterol main effect (P < 0.03). Feeding zilpaterol to heifers increased 28% adjusted final BW. Averaged across duration, zilpaterol increased (P = 0.03) 28% adjusted final BW by 19 kg compared with no zilpaterol. When compared over the different quality grades of the carcasses, zilpaterol did not affect (P 0.05) predicted empty body fat percentage of the heifer carcasses. However, zilpaterol decreased (P = 0.01) observed empty body fat percentage of low Choice carcasses by 2.88 percentage units compared with controls. Observed empty body fat percentage was not affected in heifer carcasses for any other quality grades. The effect of zilpaterol hydrochloride on the relationship between observed and predicted empty body fat percentage was tested using heifer carcasses (Figure 3). The regression equation for control heifers (line a) was y = –8.31 ± 3.82 + 1.36 ± 0.13x (R2 = 0.69; root mean square error = 2.50). The regression equation for heifers fed zilpaterol hydrochloride was y = –0.13 ± 5.42 + 1.02 ± 0.19x (R2 = 0.37; root mean square error = 2.96).
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Steers.
There were no zilpaterol x duration of zilpaterol feeding interactions (P 0.17) or duration of zilpaterol feeding effects (P 0.39) for sensory and WBSF data in steers (Table 5). Feeding zilpaterol hydrochloride increased WBSF (P < 0.001) by 22% and decreased (P 0.03) overall trained sensory tenderness by 11% and flavor intensity scores by 4%. Trained sensory scores of zilpaterol-treated steers averaged slightly to moderately tender and moderately intense for overall trained sensory tenderness and flavor intensity scores, respectively. In addition, trained sensory overall juiciness scores tended (P = 0.06) to be decreased. Cooking loss percentage of the LM steaks and trained sensory panel scores for beef flavor were not affected (P 0.43) in steers fed zilpaterol.
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0.08) or duration of zilpaterol feeding effects (P 0.15) for sensory and WBSF data in heifers (Table 6). Feeding zilpaterol hydrochloride increased (P = 0.003) WBSF by 24% and decreased (P 0.02) overall juiciness, flavor intensity, and beef flavor trained sensory panel scores. Trained sensory scores of zilpaterol-treated heifers averaged slightly to moderately juicy, moderately to very intense, and moderately to very characteristic for overall juiciness, flavor intensity, and beef flavor trained sensory panel scores, respectively. Trained sensory panel scores for overall tenderness tended to be decreased (P = 0.06) when zilpaterol was fed to heifers.
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DISCUSSION |
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TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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first reported that zilpaterol hydrochloride treatment of steers significantly improved carcass cutability of boneless, closely trimmed subprimal cuts including the neck, inside skirt, top sirloin, knuckle, and top round. In agreement, Hilton et al. (2009) reported that zilpaterol treatment of steers resulted in a significant increase in subprimal cutability of the shoulder clod, chuck tender, knuckle, top round, outside round, eye of the round, strip loin, top sirloin butt, bottom sirloin butt, ball tip, full tenderloin, and flank steak, whereas trimmable fat was decreased. However, Avendaño-Reyes et al. (2006) showed that zilpaterol treatment of steers in Mexico did not affect percentage lean, fat, or bone when carcasses were dissected. The lack of effect on carcass composition in the Avendaño-Reyes et al. (2006) may have been because of the low 60 mg/animal per day dose of zilpaterol or perhaps the genetic make-up of the cattle (approximately 20% Bos indicus) when compared with the present study and studies by Hilton et al. (2009) and Plascencia et al. (1999). In the present experiment, steer and heifer carcasses were dissected and all soft tissue was homogenized and chemical analysis conducted. Zilpaterol hydrochloride increased soft tissue protein concentration of carcasses in the present study, and increased protein to bone ratio, which would be indicative of increased lean deposition and meat cutability. However, the βAA zilpaterol did not affect carcass fat or protein to fat ratio in the present study, and only tended to affect carcass moisture, ash, and bone percentages. In contrast to the present study, Hilton et al. (2009) reported that estimated carcass fat from 9th, 10th, and 11th rib dissections was significantly decreased, whereas estimated carcass moisture was significantly increased by zilpaterol treatment. Thus, the present study indicates that zilpaterol hydrochloride functions as a repartitioning agent mainly through increased protein and muscle deposition.
Evidence of other βAA repartitioning capacity in cattle is well documented. An increase in carcass protein and moisture with a decrease in carcass fat percentage has been shown with clenbuterol (Ricks et al., 1984), cimaterol (Boucqué et al., 1994; Fiems et al., 1995; Dawson et al., 1997), and ractopamine (Parrott et al., 1990; Schroeder et al., 2003b,c). Additionally, Moloney et al. (1990) showed an increase in lean and a decrease in fat due to treatment with the βAA L644,969. Typically, use of other βAA has not affected carcass ash percentage (Dawson et al., 1997; Schroeder et al., 2003b,c), which is similar to the effect of zilpaterol treatment in the present study. In addition, carcass percentage bone was shown to be decreased in heifers of the present study and by other βAA because of an increase in soft tissue mass (Fabry and Sommer, 1990; Moloney et al., 1990).
Use of other βAA has resulted in an increase in lean to bone ratio and decreases in lean to fat ratio (Moloney et al., 1990; Dawson et al., 1997). The present study data indicated that zilpaterol is a repartitioning agent, although not as strong as other β2-agonists. In the present study zilpaterol hydrochloride resulted in an increase in carcass protein deposition, whereas fat deposition was not affected. However, Hilton et al. (2009) noted a decrease in trimmable fat from wholesale cuts from steers fed zilpaterol. Although zilpaterol hydrochloride treatment of cattle has been shown (Casey et al., 1997b; Hilton et al., 2009) to decrease trimmable subprimal fat, differences in trimmable fat due to the βAA treatment are apparently not large enough to significantly decrease total carcass fat percentage. In contrast, other β2-agonists have their strongest repartitioning effect reflected in a decrease in carcass fat percentage. Thus, zilpaterol hydrochloride is a β2-agonist and repartitioning agent that primarily functions through an increase in protein deposition, which is in agreement with the complementary carcass data (Montgomery et al., 2009).
Guiroy et al. (2002) reported that increasing the anabolic implant dose increased the BW at which animals reached 28% empty body fat. Using the same approach, we calculated empty body fat and final shrunk BW adjusted to 28% empty body fat for steers fed zilpaterol during the last 25 or 45 d on feed. Similar to the data in implanted cattle, our data indicate that steers fed zilpaterol would reach the same empty body fat (as percentage of empty BW) at a greater BW compared with animals not fed zilpaterol. Calculated percentage empty body fat was 0.95-percentage-units less for steers fed zilpaterol, resulting from decreased 12th-rib fat thickness and quality grade, and increased HCW and LM area. Similarly, feeding zilpaterol for 30 d to steers decreased calculated percentage empty body fat by 0.70 percentage units (Hilton et al., 2009). These data suggest that zilpaterol increases mature body size of steers compared with steers not fed zilpaterol at a common body composition (Guiroy et al., 2002). Additionally, the current study indicated that 28% adjusted final BW of heifers was increased by zilpaterol, although calculated empty body fat percentage of heifers was not affected by zilpaterol. The present study seems to indicate that the formulas presented by Guiroy et al. (2002) for predicting empty body fat percentage using carcass data are accurate when compared with the observed tissue fat data collected in the dissection work in the present study (R2 = 0.55). However, predicted empty body fat tended to be numerically decreased when compared with predicted empty body fat of heifers. The tendency for the equations for calculating empty body fat percentage may tend to underestimate empty body fat percentage of heifers as only 10.8% of the data used to derive the original equations included carcass data from heifers (Guiroy et al., 2001).
Several other βAA have been shown to increase beef shear force including clenbuterol (Miller et al., 1988; Schiavetta et al., 1990; Luño et al., 1999), ractopamine when supplemented at 300 mg/animal per day (Schroeder et al., 2003a), and cimaterol (Fiems et al., 1990, 1995; Vestergaard et al., 1994). Clenbuterol has also been reported to increase meat compression and stress to such a degree that samples were never similar to controls even after significant postmortem aging (Berge et al., 1993). Additionally, treatment of steers and heifers with 300 mg/animal per day of ractopamine decreased initial and sustained tenderness sensory panel scores, whereas juiciness, beef flavor, and off-flavor were not affected by treatment (Schroeder et al., 2003a).
Zilpaterol increased LM WBSF in the present study. Additionally, trained sensory traits of tenderness, juiciness, and flavor intensity were decreased or tended to be decreased for steers and heifers fed zilpaterol. Effects on juiciness, flavor intensity, and beef flavor may have been attributable to alterations in the protein structure or function caused by zilpaterol treatment. Other reports on zilpaterol hydrochloride effects on beef tenderness have varied. For example, Strydom et al. (1998), Morón-Fuenmayor et al. (2002), Avendaño-Reyes et al. (2006), and Hilton et al. (2009) reported zilpaterol hydrochloride effects on LM shear force and sensory panel factors that were similar to the results of the present study. In contrast, Casey et al. (1997a, b) reported that zilpaterol hydrochloride did not affect LM WBSF. Increased WBSF values due to zilpaterol supplementation of cattle have been shown to be reduced with postmortem aging and electrical stimulation (Strydom and Nel, 1999; Hilton et al., 2009) in both LM and semitendinosus steaks. In the study reported by Hilton et al. (2009), although the zilpaterol βAA treatment decreased tenderness and increased LM WBSF, consumer acceptability was not different between the βAA and control steaks. Zilpaterol hydrochloride affects beef tenderness and other sensory traits, although effects of zilpaterol treatment on WBSF values tend to be below the limits that lead to diminished consumer acceptance (Miller et al., 2001). In the study by Hilton et al. (2009) zilpaterol treatment increased LM WBSF similar to the results in this study; however, consumer acceptability of zilpaterol treated beef was not negatively affected even though consumers could detect tenderness differences between control and zilpaterol-treated samples.
In conclusion, it seems from this experiment that feeding of the βAA zilpaterol hydrochloride for 20 to 40 d before slaughter at 8.3 mg/kg (DM basis) increases carcass muscle deposition and protein accretion as indicated by an increase in soft tissue protein. Zilpaterol hydrochloride is a repartitioning agent that functions through increased protein and muscle deposition; other composition factors of moisture, fat, and ash seem to be minimally or not affected. Although improvements in carcass composition are also associated with a decrease in sensory traits and an increase in meat shear force, protein deposition and lean muscle growth are enhanced in steers and heifers fed zilpaterol hydrochloride during the last 20 to 40 d of the finishing period.
1 Corresponding author: jayden.montgomery{at}targacept.com
Received for publication May 11, 2008. Accepted for publication September 24, 2008.
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LITERATURE CITED |
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TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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J. L. Montgomery, C. R. Krehbiel, J. J. Cranston, D. A. Yates, J. P. Hutcheson, W. T. Nichols, M. N. Streeter, D. T. Bechtol, E. Johnson, T. TerHune, et al. Dietary zilpaterol hydrochloride. I. Feedlot performance and carcass traits of steers and heifers J Anim Sci, April 1, 2009; 87(4): 1374 - 1383. [Abstract] [Full Text] [PDF]
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