Effects of ractopamine hydrochloride and zilpaterol hydrochloride ...

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Nov 24, 2014 - (114, Teres major removed); beef chuck shoulder tender. (IM; 114F); chuck ..... type II muscle fibers to β-agonists (Smith et al., 1995) and the ...

Published November 24, 2014

Effects of ractopamine hydrochloride and zilpaterol hydrochloride supplementation on carcass cutability of calf-fed Holstein steers1 S. T. Howard,*2 D. R. Woerner,*3 D. J. Vote,† J. A. Scanga,‡ R. J. Acheson,* P. L. Chapman,§ T. C. Bryant,# J. D. Tatum,* and K. E. Belk* *Department of Animal Science, Colorado State University, Fort Collins 80523-1171; †JBS USA, LLC., Greeley, CO 80634; ‡Elanco Animal Health, Greenfield, IN 46140; §Department of Statistics, Colorado State University, Fort Collins 80523-1877; #JBS Five Rivers Cattle Feeding, LLC., Greeley, CO 80634

ABSTRACT: Effects of ractopamine hydrochloride (RH) and zilpaterol hydrochloride (ZH) on saleable yield of carcass sides from calf-fed Holstein steers were evaluated using steers implanted with a progesterone (100 mg) plus estradiol benzoate (10 mg) implant followed by a terminal trenbolone acetate (200 mg) plus estradiol (40 mg) implant. Steers were blocked by weight into pens (n = 32) randomly assigned to one of four treatments: control, RH fed at 300 mg∙steer-1/d-1 (RH 300) or RH fed at 400 mg∙steer-1/d-1 (RH 400) the final 31 d of finishing, and ZH fed at 60 to 90 mg∙steer-1/d-1 (7.56 g/ton on a 100% DM basis) for 21 d with a 5 d withdrawal before harvest. Eight to nine carcass sides were randomly selected from each pen; carcass sides with excessive hide pulls, fat pulls or bruises were avoided. Cutout data were collected within a commercial facility using plant personnel to fabricate sides at a rate of one every 3 to 4 min into items typically merchandised by the facility. All lean, fat and bone were weighed and summed back to total chilled side weight with a sensitivity of ± 2% to be included in the data set. Compared to controls, β-agonists increased

saleable yield of whole-muscle cuts by 0.61%, 0.86% and 1.95% for RH 300, RH 400 and ZH, respectively (P < 0.05). Percent fat was less in carcasses from the ZH treatment compared to controls (P < 0.05); however, this difference was not observed between RH treatments and controls (P > 0.05). Percent bone was less in the ZH treatment due to increased muscle (P < 0.05). The percent of chilled side weight comprised of trimmings was unchanged between treatments, but on a 100% lean basis, RH 400 and ZH increased trim yields (P < 0.05). Analysis of saleable yield by primal showed a fundamental shift in growth and development. Beta-agonists caused a shift in proportion of saleable yield within individual primals, with a greater portion produced from the hindquarter relative to the forequarter, specifically in those muscles of the round (P < 0.05). Beta-agonists increased saleable yield, but these effects were not constant between all major primals. The cutout value gained by packers as a result of β-agonist use may be influenced more by reduced fatness and increased absolute weight if musculature is primarily increased in the lower priced cuts of the carcass.

Key words: calf-fed Holstein, ractopamine, steer, subprimal yield, zilpaterol © 2014 American Society of Animal Science. All rights reserved. J. Anim. Sci. 2014.92:369–375 doi:10.2527/jas2013-7104 INTRODUCTION Beta-agonists have been reported to increase subprimal yield of cattle bred specifically for beef pro1This project was funded by Elanco Animal Health, a Division of

Eli Lilly and Company and JBS USA. 2Present address: Department of Animal Science, Colorado State University, Fort Collins, 80523-1171 3Corresponding author: [email protected] Received September 2, 2013. Accepted October 21, 2013.

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duction (Avendaño-Reyes et al., 2006; Scramlin et al., 2010; Arp, 2012). Specific to calf-fed Holstein steers, improvements in cutability following β-agonist use have been documented in populations fed zilpaterol hydrochloride (ZH), but have never been explored in a contemporary group fed both ractopamine hydrochloride (RH) and ZH. Work that has evaluated the effect of ZH on subprimal yield of calf-fed Holstein steers found improved cutability in cattle fed ZH (Boler et al., 2009; Garmyn et al., 2010), with substantial increases in percent of HCW comprised of cuts of the round and

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loin (Boler et al., 2009), as well as decreased percent fat and bone (Garmyn et al., 2010). Haneklaus et al. (2011) determined that the cutability advantage gained from use of ZH in calf-fed Holstein steers was primarily achieved in the carcass to subprimal cutout, but not in the subprimal to retail conversion. This indicated that β-agonists add weight; however, the retailer may be purchasing cuts that are simply heavier, not more profitable in terms of retail yield. Rathmann et al. (2009) found increased cutability in carcasses of beef-breed cattle supplemented with ZH, and noted that the most dramatic changes occurred in muscles of the round. Little doubt surrounds the ability of β-agonists to improve subprimal yield; however, if a majority of change occurs in less valuable cuts of the round, the ultimate value of these compounds to the beef industry may be reduced. The objective of this study was to determine the effect of both RH and ZH on subprimal yield of calf-fed Holstein steers. MATERIALS AND METHODS Animal handling protocols at the feedlot met the standards published in the Guide for the Care and Use of Agricultural Animals in Agricultural Research and Teaching (FASS, 1999). Experimental Design Steers were fed for a total of 360 to 380 d in southern AZ, finished during November and December 2012, and harvested at a nearby commercial facility. On arrival, steers were implanted with a progesterone (100 mg) plus estradiol benzoate (10 mg) combination implant (Synovex®-C; Zoetis, Florham Park, NJ). Steers were re-implanted with a terminal trenbolone acetate (200 mg) plus estradiol (40 mg; Revalor®-XS; Merck Animal Health, Summit, NJ) implant and blocked by weight into pens (n = 32) of 90 steers each. Eight blocks were present in the study with each treatment represented once within each block. Pens within blocks were randomly assigned to 1 of 4 treatments: no β-agonist (control), RH fed at 300 mg∙steer-1/d-1 (RH 300) for the final 31 d of finishing, or RH fed at 400 mg∙steer-1/d-1 (RH 400) as a top dress for the final 31 d of finishing, and ZH fed at 60 to 90 mg∙steer-1/d-1 (7.56 g/ton on a 100% DM basis) for 21 d with a 5-d withdrawal before harvest. Slaughter and Carcass Sampling Steers were harvested over four wk with two pens/ treatment represented each week. Steers were harvested by pen, in random order, under inspection by USDA-FSIS. Carcasses were exposed to electrical stimulation before being chilled for 48 h. Carcasses were ribbed between the 12th and 13th rib and grade data were collected online us-

ing a portable VBG 2000 VIA system (e+v Technology GmbH and Co. KG, Oranienburg, Germany). Nine carcasses per pen were randomly selected for subprimal yield determination. Carcass sides that had excessive trim, hide pulls, or abnormalities such as “fat-pulls” were excluded. Cutout data were collected within a commercial facility using plant personnel to fabricate sides into items typically merchandised by the facility. Subprimals evaluated, with NAMP number listed parenthetically, included the following: boneless chuck eye (116A, PSO 1); shoulder clod (114, Teres major removed); beef chuck shoulder tender (IM; 114F); chuck tender (IM; 116B); short ribs (130); under blade center-cut (IM; 116G, PSO 1); deckle-off, boneless (120); ribeye, lip-on (112A); back ribs (124); short ribs (123); rib fingers (124A); hanging tender (140); blade meat (109B); short plate (121); outside skirt (IM; 121C); inside skirt (IM; 121D); strip loin, boneless (180, PSO 5); top sirloin butt, boneless (184); bottom sirloin butt, tri-tip, boneless, defatted (IM; 185D); tenderloin, full, side muscle on, defatted (189A); bottom sirloin butt, flap, boneless (IM; 185A); steak tail (176); top (inside), cap off (169A); outside round (flat; 171B); eye of round (IM); 171C); outside round, heel (171F, PSO 1); Superficial digital flexor, bell knuckle (Quadriceps), flank steak (193); and Cutaneous omobrachialis. Sides were fabricated at a rate of one side every 3 to 4 min in ascending order of quality grade with no randomization of lot within Quality Grade. Chilled side weight was collected on entry onto the fabrication floor; primal weights were obtained for each carcass side; subprimal, trim, fat, and bone weights were summed back to chilled side weight with an acceptability range for weigh back (i.e., the sum of all of the parts in relation to the initial weight) of ± 2.0%. Trim was evaluated for percent fat using a MeatMaster (FOSS, Hilleroed, Denmark). Trim samples were evaluated by the MeatMaster in plastic bags that contained trim components from each carcass side. Statistical Methods Plots of residuals and the W-statistic (Shapiro and Wilk, 1965) were evaluated to determine homogeneity of variance and normality for all data. Denominator degrees of freedom were calculated using the Kenward-Roger approximation (Kenward and Roger, 1997) and means were separated using pairwise t tests and a significance level of 0.05. The software SAS 9.3 (SAS Inst. Inc., Cary, NC) was used for all data analysis. Mixed models were analyzed using the MIXED procedure. Cutout data were analyzed using a mixed model that included random block and fabrication day effects. Models included a random treatment by block interaction to separate an appropriate pen-level error term for testing treatment effects. Models used to evaluate developmental changes as a result of β-agonists included a covariate for whole-muscle saleable yield.

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Beta-agonist, cutability, Holstein, yield

Table 1. Percent of chilled side weight comprised of saleable yield, trim, fat and bone in carcasses from calf-fed Holstein steers managed with or without supplementation in the diet with beta-agonists

Subprimal Yield2 Round Loin Rib Chuck Forequarter Hindquarter Trim Fat Bone a–dLeast

Control 0.00c 0.00d 0.00b 0.00 0.00ab 0.00a 0.00c 0.00 0.00a 0.00a

Treatment1 RH 300 RH 400 0.61b 0.86b 0.22c 0.54b -0.07b 0.10ab -0.22 -0.24 0.04a -0.28bc -0.18a -0.51b 0.14c 0.64b 0.04 0.01 -0.56a -0.63a -0.17a -0.30ab

ZH 1.96a 1.0a 0.23a -0.24 -0.52c -0.76b 1.22a -0.02 -1.32b -0.69b

SEM 0.18 0.12 0.06 0.08 0.11 0.11 0.12 0.24 0.25 0.19

Treatment < 0.0001 < 0.0001 0.0141 0.1037 0.0017 0.0002 < 0.0001 0.9620 0.0054 0.0106

P-Value β-Agonist 0.0003 0.0028 0.3278 0.0270 0.0963 0.0031 0.0038 0.8811 0.0032 0.0402

RH vs. ZH < 0.0001 0.0020 0.0205 0.9027 0.0101 0.0141 < 0.0001 0.6836 0.0076 0.0134

squares means within a row lacking a common letter superscript differ (P < 0.05).

1Control—implanted with Revalor®-XS; RH 300—Revalor®-XS + Ractopamine hydrochloride (RH) at 300 mg/hd/d; RH 400—Revalor®-XS + RH at 400 mg/

hd/d; ZH—Revalor®-XS + Zilpaterol hydrochloride at 7.56 g/ton on a 100% DM basis. 2Saleable yield from whole muscle cuts, division by primal represents percent of total saleable yield accounted for by each major primal.

RESULTS AND DISCUSSION To preface, works that have evaluated subprimal cutout yields of cattle fed β-agonists have typically investigated only one of the two commercially available compounds (Boler et al., 2009; Holmer et al., 2009; Kellermeier et al., 2009; Rathmann et al., 2009; Garmyn et al., 2010; Hilton et al., 2010), applied these compounds to only populations comprised of beef breeds (Arp, 2012), or used carcass sampling procedures that were not totally random. This study is the only work that has evaluated both commercially available β-agonists in calf-fed Holsteins, determined subprimal yield based on data generated within a commercial facility, and done so using selection criteria that were totally random. Although not presented here, treatment had no effect on marbling score of the sample population (P > 0.05; Howard, 2013). Compared to controls, β-agonists increased saleable yield of whole-muscle cuts by 0.61%, 0.86%, and 1.95% for RH 300, RH 400, and ZH, respectively (P < 0.05; Table 1). Percent fat was lower in carcasses from the ZH treatment compared to controls (P < 0.05); however, this difference was not observed between RH treatments and controls (P > 0.05). Percent bone was lower in the ZH treatment due to increased muscle (P < 0.05). The percent of chilled side weight comprised of trimmings was unchanged between treatments (P < 0.05), but on a 100% lean basis, RH 400 and ZH increased trim yields (P < 0.05; Table 2). Analysis of saleable yield by primal showed a fundamental shift in growth and development. Beta-agonists caused a shift in distribution of saleable yield by primal, with a greater portion produced from the hindquarter relative to the forequarter (P < 0.05; Table 1; Fig. 1). In bovine animals, although increases in animal size and weight may occur (such as those following admin-

istration of hormone-based implants), the proportion of total musculature comprised of individual muscle groups remains relatively constant between animals (Berg and Butterfield, 1976). In contrast, findings of the present study suggest that β-agonists cause a shift in muscle growth and development patterns. Beta-agonists increased the proportion of whole-muscle saleable yield comprised of muscles of the hindquarter relative to those of the forequarter, specifically affecting muscles of the round (Fig.  1). Of the weight added to total whole-muscle saleable yield as a result of β-agonist use, almost half was found in the round (Fig. 2). Berg and Butterfield (1976) summarized works that primarily used whole carcass dissection to calculate total muscle weight. The present study did not result in separation of the carcass into individual muscles totally trimmed of fat and connective tissue; however, the weight of cuts that were relatively free of seam fat depots (shoulder clod [114, Teres major removed]; beef chuck shoulder tender [IM; 114F]; chuck tender [IM; 116B]; outside skirt [IM; 121C]; inside skirt [IM; 121D]; strip loin, boneless [180, PSO 5]; top sirloin butt, boneless [184]; bottom sirloin butt, tri-tip, boneless, defatted [IM; 185D]; tenderloin, full, side muscle on, defatted [189A]; bottom sirloin butt, flap, boneless [IM; 185A]; top [inside], cap off [169A]; outside round [flat; 171B]; eye of round [IM; 171C]; outside round, heel [171F, PSO 1]; Superficial digital flexor; bell knuckle; flank steak [193]) all increased with increasing weight of total saleable yield (P < 0.05). Models including effects of β-agonist treatment and the weight of total saleable yield as a covariate showed that only the weights of the round heel, eye of round, top round, loin flap, and Teres major increased as dose and potency of β-agonist increased (P < 0.05). Use of total saleable yield as a covariate adjusted all observations to a compositionally equal endpoint in terms

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Table 2. Subprimal yield of carcasses from calf-fed Holstein steers managed with or without supplementation in the diet with beta-agonists1 Item (NAMP #) Chuck Eye (116A, PSO 1) Bone-In Short Rib (130) Chuck Flap (116G, PSO 1) Pectoral Shank Meat- Forequarter Clod (114)3 Chuck Tender (116B) Teres Major (114F) Brisket (120) Total Chuck Trim Total Chuck Fat Total Chuck Bone Ribeye Roll (112A) Back Ribs (124) Short Rib (123) Lifter Meat (109B) Hanging Tender (140) Rib Fingers (124A) Total Rib Fat Total Rib Trim Total Rib Bone Navel (121) Outside Skirt (121C) Inside Skirt (121D) Strip Loin (180, PSO 5) Top Butt (184) Tri-Tip (185D) Flap Meat (185A) Tenderloin (189A) Flank (193) Rose Meat Total Loin Fat Total Loin Trim Total Loin Bone Top Round (169A) Bottom Round (171B) Eye of Round (171C) Quadriceps/Bell Knuckle Heel (171F, PSO 1) Superficial digital flexor Shank Meat- Hindquarter Total Round Trim Total Round Fat Total Round Bone 100% Lean Trim4 a–cLeast

Control 0.00 0.00 0.00 0.00b 0.00 0.00b 0.00b 0.00b 0.00 0.00 0.00a 0.00a 0.00b 0.00 0.00 0.00b 0.00 0.00 0.00 0.00 0.00 0.00a 0.00 0.00 0.00 0.00c 0.00c 0.00 0.00b 0.00c 0.00 0.00a 0.00 0.00 0.00c 0.00c 0.00c 0.00c 0.00c 0.00b 0.00b 0.00b 0.00a 0.00a 0.00c

Treatment2 RH 300 RH 400 0.03 -0.01 0.01 0.01 0.00 -0.02 0.01b 0.01b 0.03 0.02 0.10a 0.07ab 0.01ab 0.02a 0.02a 0.01b 0.03 0.01 0.05 0.00 -0.05ab -0.14bc -0.04a -0.14ab 0.02b 0.07ab -0.01 -0.01 0.00 0.00 0.02b 0.02b -0.05 -0.07 -0.01 0.00 -0.11 -0.10 -0.05 -0.05 -0.04 -0.05 -0.05ab -0.09bc 0.01 0.01 0.01 0.02 -0.03 0.03 0.01bc 0.07b 0.04b 0.04b 0.03 0.03 0.02b 0.03b 0.01bc 0.02b 0.05 0.04 -0.22b -0.16b 0.05 0.05 -0.02 -0.05 0.09b 0.16b 0.07bc 0.11b 0.03bc 0.07b 0.05bc 0.11ab 0.01bc 0.03b 0.00ab 0.01a 0.02b 0.01b 0.12a 0.17a -0.11bc -0.08b -0.04a -0.04a 0.31bc 0.52ab

ZH 0.06 -0.02 0.00 0.04a 0.00 0.12a 0.03a 0.03a 0.04 0.00 -0.21c -0.28b 0.11a -0.03 -0.02 0.10a 0.00 0.00 -0.12 -0.11 -0.09 -0.16c 0.00 0.03 0.14 0.16a 0.07a 0.02 0.08a 0.04a 0.06 -0.46c 0.08 -0.09 0.37a 0.24a 0.14a 0.18a 0.07a 0.01a 0.08a 0.17a -0.21c -0.19b 0.73a

SEM 0.06 0.02 0.01 0.01 0.05 0.03 0.01 0.003 0.03 0.09 0.05 0.07 0.03 0.02 0.03 0.02 0.02 0.01 0.08 0.10 0.03 0.04 0.01 0.01 0.02 0.03 0.01 0.01 0.02 0.01 0.03 0.09 0.08 0.03 0.03 0.03 0.02 0.03 0.01 0.004 0.03 0.04 0.04 0.04 0.21

Treatment 0.4985 0.4425 0.1200 0.0055 0.8617 0.0343 0.0090 < 0.0001 0.3432 0.9312 0.0033 0.0385 0.0293 0.1668 0.3457 0.0004 0.0839 0.9530 0.1916 0.1300 0.0603 0.0093 0.1093 0.0765 0.2345 < 0.0001 0.0002 0.0864 0.0080 0.0003 0.1361 0.0014 0.4019 0.2178 < 0.0001 < 0.0001 < 0.0001 0.0002 < 0.0001 0.0194 0.0418 0.0076 0.0068 0.0026 0.0085

P-Value β-Agonist 0.3934 0.8496 0.4065 0.0442 0.6678 0.0023 0.0020 0.0046 0.2253 0.7583 0.0426 0.0906 0.0509 0.1297 0.6541 0.0246 0.1613 0.6900 0.0797 0.0996 0.0634 0.0090 0.0393 0.0256 0.4139 0.0165 0.0002 0.0134 0.0076 0.0021 0.0302 0.0067 0.1320 0.1586 0.0005 0.1746 0.1851 0.0018 0.0143 0.0052 0.1104 0.0158 0.0101 0.0728 0.0051

RH vs. ZH 0.3033 0.1019 0.4242 0.0047 0.5031 0.3093 0.0749 0.0056 0.3144 0.7681 0.0297 0.0294 0.0164 0.1314 0.0303 0.0003 0.2604 0.8117 0.7423 0.0607 0.1126 0.0024 0.1535 0.2025 0.0004 0.0005 0.0103 0.3742 0.0044 0.0025 0.8516 0.0092 0.4815 0.1764 < 0.0001 0.0004 0.0008 0.0104 < 0.0001 0.3701 0.0203 0.6378 0.0285 0.0011 0.1092

squares means within a row lacking a common letter superscript differ (P < 0.05). expressed as a percent change from control of total chilled side weight. 2Control—implanted with Revalor®-XS; RH 300—Revalor®-XS + Ractopamine hydrochloride (RH) at 300 mg/hd/d; RH 400—Revalor®-XS + RH at 400 mg/hd/d; ZH– Revalor®-XS + Zilpaterol hydrochloride at 7.56 g/ton on a 100% DM basis. 3Teres major removed. 4100% Lean Trim = (% trim of chilled side weight)*(trim % lean). Trim percent lean calculated based on output from a MeatMaster (FOSS, Hilleroed, Denmark). 1Values

Beta-agonist, cutability, Holstein, yield

Figure 1. Change from Control in distribution of total saleable yield comprised of whole-muscle cuts from each primal of calf-fed Holstein steers managed with or without supplementation in the diet with β-agonists. Control—implanted with Revalor®-XS; RH 300—Revalor®-XS + Ractopamine hydrochloride (RH) at 300 mg/hd/d; RH 400—Revalor®-XS + RH at 400 mg/hd/d; ZH—Revalor®-XS + Zilpaterol hydrochloride at 7.56 g/ ton on a 100% DM basis. Least squares means not lacking a common letter superscript differ (P < 0.05), those with an (*) do differ from Control.

of total musculature. Berg and Butterfield (1976) summarized that the percentage of total musculature comprised of different muscles of the carcass did not differ between “highly improved” breeds of domesticated cattle and farel populations that had no influence of genetic selection for over 70 yr. The finding of Berg and Butterfield (1976) indicated that development is influenced by total weight, but, proportionally, the tissue distribution of muscles is comparable among cattle of diverse phenotype and genotype. Consequently, when total saleable yield was used as a covariate, the effect of β-agonist treatment should have been nonsignificant if β-agonists only resulted in increased muscle size and muscle weight. This was obviously not true; however, the muscles that were influenced by β-agonists independent of total weight of saleable yield were not among the more valuable cuts of the carcass, potentially indicating the advantages gained by β-agonist use are more limited than some previous works have reported. Trends found in some muscle groups for the effect of increasing dose and potency of β-agonists reported in Table 2 were actually reversed when total saleable yield was used as a covariate. The clod was heavier in control and RH 300 treatments when weight of total saleable yield was used as a covariate (P < 0.05), and weight of the strip loin was not different between control and ZH treatments when the same covariate was included (P < 0.05). These findings indicated that increased size of individual muscles following feeding of β-agonists is relatively proportional to the changes in total musculature, except in the round heel, eye of round, top round, loin flap, and Teres major. The differing effects of β-agonists on individual muscle groups could be due to increased sensitivity of

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Figure 2. Distribution of whole-muscle saleable yield added from controls by primal in calf-fed Holstein steers managed with or without supplementation in the diet with β-agonists. Control—implanted with Revalor®-XS; RH 300—Revalor®-XS + Ractopamine hydrochloride (RH) at 300 mg/hd/d; RH 400—Revalor®-XS + RH at 400 mg/hd/d; ZH—Revalor®XS + Zilpaterol hydrochloride at 7.56 g/ton on a 100% DM basis.

type II muscle fibers to β-agonists (Smith et al., 1995) and the relatively high content of white muscle fibers in muscles of the hindquarter (Kirchofer et al., 2002). However, the changes in development observed in the present study were not identical to those found by Arp (2012), who explored the same growth promotants in a population of beef-breed type steers. The different response to β-agonists based on breed type could be due to muscle fiber demographics; however, published research has reported conflicting evidence to support this hypothesis. Spindler et al. (1980) reported that smaller diameters of white muscle fibers were present in Holstein steers compared to Angus and Hereford cattle. The same study also reported relatively unchanged percentages of white muscle fibers between breeds (Spindler et al., 1980). If the white fibers present in Holstein steers are indeed smaller, they could lend themselves more readily to muscle hypertrophy. However, if percentage is more important, these findings may not support increased response of Holstein steers to β-agonists. Dreyer et al. (1977) reported an increased percentage of type II fibers in Holstein cattle compared to Afrikaner cattle, a Bos indicus breed that may not be comparable to breeds traditionally used in the U.S. for beef production. Other studies have reported that an increased plane of nutrition can result in a greater percentage of type II muscle fibers (Seideman and Crouse, 1986). Management of calf-fed Holstein steers dictates higher planes of nutrition throughout life compared to those of beef breeds. This, coupled with the potential for increased percentages of white muscle fibers, could explain an increased sensitivity of Holstein steers to β-agonists. If calf-fed Holstein steers are indeed more sensitive to β-agonists, this could result in added return on investment for producers supplementing Holstein steers with β-agonists.

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Howard et al.

Changes in development were reflected by an increased percentage of chilled side weight comprised of muscles from the round when calf-fed Holstein steers were treated with β-agonists (P < 0.05; Table 2). Top round, bottom round, eye of round, heel, and knuckle subprimals all comprised a greater percentage of chilled side weight in RH 400 and ZH treatments compared to controls (P < 0.05), and top round, bottom round, eye of round, and heel comprised a greater percent of chilled side weight in ZH-treated cattle than in any other treatment (P < 0.05). Previous research has reported nearly identical findings in Holstein steers and beef breeds supplemented with ZH and/ or RH (Boler et al., 2009; Hilton et al., 2009; Kellermeier et al., 2009; Rathmann et al., 2009; Garmyn et al., 2010; Hilton et al., 2010; Scramlin et al., 2010; Arp, 2012). The current findings are in relative agreement with the previous studies in that the loin flap, or Obliquus abdominis interni, was not affected by β-agonists, except when weight of total saleable yield was used as a covariate. This finding was interesting considering that Berg and Butterfield (1976) reported the Obliquus abdominis interni was a high impetus muscle, which the authors summarized to be used more heavily as weight increases. If weight is more influential to this muscle than hormone-based mediators of growth, this could explain the lack of response. Interestingly, no effect of β-agonists on the percent of chilled side weight comprised of the strip loin was observed (P > 0.05). Due to the shallow shape of the Longissimus dorsi in medial sections of the strip loin of calf-fed Holstein steers, excess subcutaneous fat may have been included in strip loins from certain treatments, which could have negated the effect of β-agonists on this cut. Carcasses from steers treated as controls or with RH did not differ in percent of chilled side weight comprised of tenderloin (P > 0.05); however, tri-tip and top sirloin butt accounted for a greater percentage of chilled side weight in RH 400 compared to controls (P < 0.05). Most loin cuts (except strip loin and loin flap) from carcasses of steers treated with ZH comprised a greater percentage of chilled side weight compared to all other treatments (P < 0.05). Relative to trim components, fat from the loin and round was lower in carcasses of steers supplemented with β-agonists (P < 0.05), but not different between RH treatments (P > 0.05). Zilpaterol hydrochloride reduced percent bone in the round (P > 0.05), but not in the loin (P > 0.05). Percent trim (100% lean basis) from the round was higher in the carcasses of steers treated with β-agonists compared to controls (P < 0.05). To summarize, increased dose or potency of β-agonists caused an increased percentage of chilled side weight to be present in the form of cuts from the hindquarter. Effects of β-agonists on the cuts of the forequarter were less pronounced. This was likely caused in part by fabrication styles that allowed for inclusion of seam fat depots within several cuts of the chuck and rib in

carcasses of nontreated steers. These depots may have artificially increased cut weight, despite advantages in lean value found in cuts derived from carcasses of steers treated with β-agonists. The current study found that the shoulder clod (Triceps brachii and Infraspinatus), Teres major, and Supraspinatus generally comprised a greater percentage of chilled side weight in RH and ZH treatments (P < 0.05). These effects were neither linear nor uniform as dose and potency of β-agonist increased, possibly indicating reduced sensitivity of these muscles to β-agonists. The dorsal portion of the deep pectoral muscle that remained attached to the under blade comprised a greater percentage of chilled side weight for carcasses of steers in the ZH treatment (P < 0.05), although no difference existed between carcasses of steers in the control and RH treatments (P < 0.05). The ribeye roll and Latissimus dorsi comprised a greater percentage of chilled side weight for carcass sides of steers in the ZH treatment (P < 0.05); however, no differences were observed between carcasses of steers treated with RH and controls in the same muscles the previous. Fat and bone from the chuck were lower for carcasses of steers in the ZH treatment relative to controls (P < 0.05), however, not different between carcasses of steers treated with RH and controls (P > 0.05). Previous works reported more mixed responses of cuts of the forequarter to ZH and RH. Boler et al. (2009) reported no differences in percent of chilled side weight comprised of cuts from the chuck following administration of ZH to calf-fed Holstein steers for 20 d. However, the same work found an increase in percent of chilled side weight comprised of the ribeye roll in carcasses from cattle fed ZH. Arp (2012) reported no effect of β-agonists on percent of chilled side weight made up of any cut from the forequarter. When ZH was administered to beef steers, several workers found similar results to those presented herein (Hilton et al., 2009; Kellermeier et al., 2009; Rathmann et al., 2009; Garmyn et al., 2010; Scramlin et al., 2010). The only thin meat (flank, inside and outside skirt) cut that increased in percent of total chilled side weight as a result of individual treatment was the flank (P < 0.05). Outside skirts were generally unchanged between treatments; however, percent of chilled side weight comprised of inside skirt tended to be higher in carcasses of cattle fed ZH. Percent of chilled side weight comprised of inside skirt was higher in β-agonist treated steers compared to controls (P < 0.05). The response of the inside skirt to ZH was reported by Kellermeier et al. (2009), Rathmann et al. (2009), Hilton et al. (2009), and Garmyn et al. (2010). However, Boler et al. (2009) and Arp (2012) reported no effect of ZH on thin meat yields. Cuts merchandized from the plate, or navels, comprised a greater percentage of chilled side weight in controls (P < 0.05), likely due to increased fat content within this cut.

Beta-agonist, cutability, Holstein, yield

Our findings were in agreement with many previous works that have reported decreased fatness and increased subprimal yields following supplementation in the diet with β-agonists. Distribution of subprimal yield was influenced by dose and potency of β-agonists, with an increased proportion of saleable yield comprised of those muscles of the round relative to the chuck. This finding represented a change in growth and development that is influential to the effect of β-agonists on cutout value. The distribution of saleable yield between the rib and loin was not consistent based on β-agonist treatment. Several cuts of the loin were influenced by β-agonists; however, those from the rib typically were not and generally accounted for a lower percent of total saleable yield in treated cattle. Beta-agonists increased weight, which clearly adds value, but it is noteworthy that this did not occur on a proportional basis between the high- and low-priced cuts of the carcass. If the weight gain in cattle fed β-agonists occurs mainly in the low-priced cuts of the round (Fig. 2) and the proportion of total saleable yield accounted for by the high-priced middle meats is mostly similar between treated and nontreated cattle (Fig. 1), the advantage β-agonists provide to packers may relate more to decreased fat and increased absolute carcass weight, and less to increased percent muscle in high-value cuts. Decreased external fat would also isolate the advantages of β-agonist use primarily to packers and not retailers since most cuts are merchandised at a standard trim level. LITERATURE CITED Arp, T. S. 2012. Effect of dietary beta-agonist supplementation on live performance, carcass characteristics, carcass fabrication yields, and strip loin tenderness and sensory traits. PhD Diss. Colo. State Univ., Fort Collins. Avendaño-Reyes, L., V. Torres-Rodríguez, F. J. Meraz-Murillo, C. Pérez-Linares, F. Figueroa-Saavedra, and P. H. Robinson. 2006. Effects of two β-adrenergic agonists on finishing performance, carcass characteristics, and meat quality of feedlot steers. J. Anim. Sci. 84:3259–3265. Berg, R. T., and R. M. Butterfield. 1976. New concepts of cattle growth. Sydney Univ. Press, Sydney, N.S.W., Australia. Boler, D. D., S. F. Holmer, F. K. McKeith, J. Killefer, D. L. VanOverbeke, G. G. Hilton, R. J. Delmore, J. L. Beckett, J. C. Brooks, R. K. Miller, D. B. Griffin, J. W. Savell, T. E. Lawrence, N. A. Elam, M.N. Streeter, W. T. Nichols, J. P. Hutcheson, D. A. Yates, and D. M. Allen. 2009. Effects of feeding zilpaterol hydrochloride for twenty to forty days on carcass cutability and subprimal yield of calf-fed Holstein steers. J. Anim. Sci. 87:3722–3729. Dreyer, J. H., R. T. Naude, J. W. N. Henning, and E. Rossouw. 1977. The influence of breed, castration and age on muscle fibre type and diameter in Friesland and Afrikaner cattle. S. Afr. J. Anim. Sci. 7:171–180. FASS. 1999. Guide for the Care and Use of Agricultural Animals in Agricultural Research and Teaching. 1st rev. ed. Fed. Anim. Sci. Soc., Savoy, IL.

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