- Email: [email protected]
Effects of Steroid Implants on the Tenderness of Beef
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The Professional Animal Scientist Nichols et al. 18 (2002):202–210
: Effects of Steroid RImplants on the EVIEW
Tenderness of Beef W. T. NICHOLS*,1 , PAS, M. L. GALYEAN†, PAS, D. U. THOMSON‡, PAS, and J. P. HUTCHESON* *Intervet, Inc., Millsboro, DE 19966, †Department of Animal and Food Sciences, Texas Tech University, Lubbock, TX 79409, and ‡Cactus Feeders, Inc., Amarillo, TX 79116
Abstract
weight restrictions, and so on. By understanding how steroid implants All cattle in the suckling through work, coupled with knowledge of growth finishing phases of production respond to physiology, cattle genetics, and the implants. In feedlot cattle, implants market, a producer can use these tools to have been reported to improve ADG by fit many different feeding and economic 15 to 25% and feed efficiency by 10 to scenarios. There has been concern in the 15%. The resulting increase in saleable industry that androgenic implants, used carcass and the associated benefits in feed alone or in combination with estrogenic efficiency make a regular, systematic implants, might decrease marbling or implant program profitable for the affect other palatability factors. Based producer. Recent research with anabolic on the data we reviewed, the currently steroid implants has demonstrated that available growth-promoting implants growth occurs normally as a result of have limited, if any, effects on tenderness concomitant increases in bone, muscle, of beef as determined by Warnerand fat, with proportions of these compo- Bratzler shear force (WBS) or taste panel nents staying relatively the same, but evaluation of tenderness. Further increased absolute amounts being research should be conducted to evaluate deposited. In addition, feeding implanted the effects of growth-promoting implants (I) cattle longer so that they may reach on calpain and calpastatin activities in physiological endpoint has been shown to muscle. compensate for decreased marbling, allowing I cattle to grade similarly to (Key Words: Beef, Tenderness, non-implanted (NI) cattle. Nonetheless, I Implants, Carcass, Steroid.) cattle would be heavier at the same physiological endpoint, which could have both positive and negative effects on Estrogenic and androgenic steroids marketing schemes. The producer can have been used for the last halfadjust implant strategies to fit variable century to enhance the efficiency of market conditions, including high vs low beef production. Since 1954, many diet costs, live BW restrictions, carcass different combinations of dosages and ratios of estrogen with other steroids have been approved for use in confined and pastured beef cattle. 1To whom correspondence should be adSteroid implants are the best availdressed: [email protected] able non-nutritional management
Introduction
tools for a producer to increase biological and economical efficiency of beef cattle (41). The efficient production of safe, wholesome, and palatable beef products might well determine the future of the beef industry. Production efficiency can be defined as the return of saleable product per unit of feed input; however, composition of the product is an increasingly important factor in determining the product unit value and cost. Although final weights are significantly different, recent research indicates that the percentage of protein, adipose, and bone is similar in implanted (I) and non-implanted (NI) animals when finished to the same physiological end point (5, 19, 37). The mechanisms involved in this increase in the growth curve of I cattle include modification of priorities for nutrient use for protein vs fat deposition, alteration of tissue turnover, modification of daily tissue deposition limits, and modification of nutrient supply (19, 37, 54). Recently, tenderness and palatability of beef products have been recognized as potentially important issues affecting the beef industry. The palatability of beef products is related to flavor, juiciness, and tenderness. Marbling is an important component of flavor and juiciness, and, because growthpromoting implants enhance both
REVIEW: Steroid Implants and Beef Tenderness
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both I and NI cattle consume enough energy to maximize fat accretion rates; hence, implants would not be expected to affect fat accretion markedly. Anabolic implants that contain estrogens, androgens, or a combination of the two do not have a direct lipolytic effect on adipose tissue. At equal physiological maturity, carcass composition will be similar between I (TBA/E2, TBA, or E2) and NI cattle (19, 37). Loy et al. (29) and Preston (40) showed that steroid implants containing estrogens increased the mature body size of steers. Both small- and large-framed steers that were implanted regularly with estrogenic steroids had increased BW gains, hip heights (40), and BW:height ratios compared with NI steers. Preston (40) fed cattle for up to 486 d, and the NI steers never equaled the I steers for hip height, indicating that estrogenic implants increase mature body size. Roeder et al. (46) reported that anabolic steroids do not directly stimulate protein synthesis in rat muscle cells, and Thomson et al. (52) found the same to be true for beef muscle cells cultured in vitro and treated directly with estradiol-17ß (E2), TBA alone, or the combination. Thomson et al. (51) treated fetal Mechanism of Action of Steroids. muscle cells with serum from steers Steroid implants increase protein implanted with TBA:E2 and bovine somatotropin (bST) alone and in synthesis and decrease protein combination. Steroids indirectly degradation. Johnson et al. (21) increased protein synthesis, with no reported that I steers [trenbolone acetate (TBA)/estradiol (E2) vs NI] had effect on protein degradation, which increased protein and bone deposiagrees with the in vivo effects of E2 and TBA on protein turnover retion relative to NI steers. Moreover, ported by Hayden et al. (14). carcass water was greater in I steers The anabolic response of rumibecause water is deposited with nants to androgens and estrogens, in protein. Johnson et al. (21) also addition to the direct effects noted reported that the anabolic implant had no effect on carcass fat accretion previously, might result from indirect actions (e.g., alterations in blood during the feeding period. At the concentrations of growth factors end of the feeding period, NI steers had decreased fat deposition, whereas such as growth hormone or soI cattle were continuing to deposit fat matomedins). Several studies have indicated that estrogens stimulate at a linear rate, indicating that the growth hormone secretion (8, 18, 54) NI cattle had reached physiological and growth hormone receptor maturity sooner than the I cattle. numbers in the liver (4). Because the Owens (38) suggested that cattle have a maximum limit for fat deposi- liver also is a primary source of somatomedins, an estrogenic stimution. During the finishing phase,
lus might ultimately increase somatomedin concentrations. Direct effects of implants via specific receptors in muscle tissue might also occur because androgen and estrogen receptors have been identified in the striated muscle of rats (27) and pigs (49), and estrogen receptors have been reported in cattle (32). Trenkle (55) reported that anabolic steroids increase the size of the pituitary and increase the number of acidophils. There are three types of acidophils located in the anterior pituitary: somatotropes [secrete growth hormone (GH)], lactotropes [secrete prolactin (PRL)], and mammosomatotropes (secrete GH and PRL). Thomson et al. (50) implanted steers 24 d before slaughter with TBA (200 mg):estradiol benzoate (28 mg). Anterior pituitaries were harvested at slaughter, and the reverse plaque assay (26) was used to examine the composition of the acidophils. Implanted steers had an increased percentage of somatotropes and a decreased percentage of mammosomatotropes relative to NI steers, but implanting had no effect on lactotropes. Implants increased the overall percentage of cells that secreted GH by 30% compared with NI steers. Therefore, TBA:E2 implants seem to be working, at least in part, through the GH pathway by increasing the size of the anterior pituitary and changing its composition by increasing the percentage of somatotropes. Some data suggest that both increased production of insulin-like growth factor-1 (IGF-I) and a higher number of actively proliferating (activated) muscle satellite cells might be involved in anabolic steroidinduced muscle growth (22, 23). Circulating concentrations of the potent anabolic growth factor IGF-I and steady-state hepatic IGF-I mRNA concentrations were significantly higher in steers implanted with a combination of TBA and E2 than in NI steers (20). Moreover, steady-state IGF-I mRNA concentrations in the longissimus (LD) of I steers were higher than in the corresponding
ADG and feed conversion, I cattle often have less marbling and lower quality grades than NI cattle when slaughtered on a time-constant basis (16, 28, 29, 30, 33, 39, 42, 48, 57). In contrast, more recent research has demonstrated that feeding I and NI cattle to equal physiological end points can alleviate these negative effects on marbling (5, 37). Therefore, flavor and juiciness have not been much of an issue because marbling seems to correlate well with these two variables (15); however, tenderness does not seem to correlate with the current quality standards for beef products. Because the issue of potential negative effects of steroid implants on beef tenderness has become a concern (45), the objective of this paper is to review the literature regarding the effects of steroid implants on the tenderness of beef. To understand the role that steroid implants might play in affecting tenderness, it is important to understand the mechanisms by which they might affect the growth physiology of cattle; thus, a brief review of the mechanism of action of steroid implants will be included.
Review and Discussion
204
muscle of NI steers. Thus, muscle tissue might produce higher concentrations of IGF-I in E2/TBA-treated steers (22). In addition, a greater number of actively proliferating satellite cells could be isolated from the semimembranosus muscle of I steers than from the corresponding muscle of NI steers (23). The ability of TBA/E2 to increase circulating and muscle IGF-I concentrations and to increase the number of activated satellite cells could play a critical role in anabolic steroid-induced muscle growth in beef cattle. Growth factors other than IGF-I, such as hepatocyte growth factor and fibroblast growth factor, also might be involved in anabolic steroid-induced muscle growth (8). How do these changes in metabolism that are responsible for increased growth in beef cattle relate to the effects of steroids on beef tenderness? The mechanism of action of steroid implants seems to be to increase protein and bone deposition through shifting the mature body size of cattle by increasing GH secretion, increasing IGF-I concentrations in the liver and muscle cells, increasing satellite cell proliferation, and so on. If implants decrease the tenderness of beef, is it also possible that largerframed, rapidly growing animals within a breed would differ in tenderness from smaller-framed animals in the same breed? Effects of frame size on beef tenderness do not seem to have been critically evaluated and might warrant further study. Effects of Implants on Tenderness. Beef tenderness is typically measured in one of two ways: 1) Warner Bratzler shear force (WBS) and 2) taste panel evaluation of tenderness. In addition, calpain and calpastatin activities in muscle tissue might be related to tenderness (13, 24). Our summary of the literature focused on WBS determinations and taste panel evaluations of tenderness. Limited data on muscle calpain and calpastatin activities were included to illustrate what is currently known about the effects of implants on these variables. Criteria used to
Nichols et al.
determine whether a study was included in this review were that the study must have included a NI control vs an I strategy in which at least one of the strategies used an implant that contained some level of TBA or a TBA implant treatment. A majority of the studies also included an estrogen-only implant treatment. These criteria were used because a majority of cattle receive a TBAcontaining implant sometime during the beef production period (9, 12). Treatments that included TBA were 1) no initial implant with a TBAcontaining implant as a final implant, 2) estrogen-only implant as the initial implant with a TBAcontaining implant as the final implant, 3) a TBA-containing implant as the initial implant with no final implant, and 4) a TBA-containing implant as both the initial and final implant. One trial was evaluated in which three implants were used, all of which contained TBA. Estrogen-only (E2) implants for this review included those that contained zeranol, Estradiol-17β, and estradiol benzoate without TBA. The TBA implants (or TBA treatments) included all implants or treatments that contained TBA. This would include TBA/E2 implants with both hormones in the same implant; TBAonly implants used in conjunction with an E2-only implant; TBA-only implants used in conjunction with melengestrol acetate (MGA), a progestin which increases endogenous estrogen through its action on the endocrine system; and TBA only. The control treatments in all studies did not receive any type of implant. Effects of Implants on WBS. Warner-Bratzler shear force has been used for many years as an index of beef tenderness. A WBS value of <3.85 kg is deemed to represent beef in the very tender category, values of 3.9 to 4.54 kg are considered tender, and a value of >4.54 kg is considered to represent tough beef (15, 35). The WBS comparisons for the published reports included in this review are shown in Table 1. There were 19 studies that met the criteria for
summarization. Three studies found a significant detrimental effect of one or more implant strategies on WBS (36, 45, 47), and two studies (25, 43) reported a positive effect of implants on WBS (lower score). Despite individual implant treatment differences from nonimplant treatments, there were no studies with multiple implant treatments in which a significant deleterious effect on WBS was noted with all implant treatments vs non-implant treatment. Samber et al. (47) reported that steaks from steers that had been implanted with TBA/E2 as the initial and the terminal implant (2X), or as the initial, intermediate, and the terminal implant (3X) had higher WBS values (P<0.05) than steaks from steers that were not implanted (2X = 3.00, 3X = 2.91, 3X = 3.00, NI = 2.58 kg, respectively). However, the WBS of steaks from steers that had an E2 implant initially, followed by a TBA/ E2 implant at time of re-implant did not differ from steaks of the control steers (2.63 and 2.58 kg, respectively). Similarly, steaks from steers implanted with two doses of E2 as the initial and intermediate implant, followed by a TBA/E2 as the terminal, or one dose of E2 as the initial and followed by two doses of TBA/E2 as the intermediate and terminal implant did not differ from steaks from NI steers (2.73, 2.74, and 2.58 kg, respectively). The authors reported that 91% of the loin steaks tested had WBS values <3.85 kg. Hence, the significance of these changes in WBS with implants to the consumer would likely be negligible. Kerth et al. (25) found that implanting heifers with TBA/E2 as the initial implant with no re-implant or TBA/ E2 as the initial implant and reimplanting with TBA/E2 decreased WBS, resulting in steaks with a lower WBS (P<0.05) than steaks from NI heifers (2.92, 3.17, and 3.48 kg, respectively). Steaks from all other implant strategies, not implanted initially and re-implantation withTBA/E2, a low dose of TBA/E2 initially and re-implantation with TBA/E2, and E2 initially and re-
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TABLE 1. Summary of published experiments that have evaluated the effects of steroid implants on WarnerBratzler shear force (WBS) values (kg). Reference
Year
N
Crouse et al. Trenkle Apple et al. Huck et al. Huffman et al. Hunt et al. Gerken et al.g Cranwell et al. Kerth et al. Milton et al. Milton et al. Nichols et al. Samber et al. Foutz et al.h Beirman et al. Pruneda et al. Pritchard Roeber et al. Kerth et al.
1987 1990 1991 1991 1991 1991 1995 1996 1996 1996 1996 1996 1996 1997 1999 1999 2000 2000 2002
77 150 72 80 46 30 24 60 12 480 216 600 560 140 480 100 310 298 320
Sexa
Control
E2b
h s s s s s s cc s s s h s s s s s s h
5.45 2.86 4.01 3.68 4.82 3.40 4.16 5.10w 2.07 3.64 3.85 3.71w 2.58w 4.00 5.41 3.38 4.02x 2.97w 3.49w
— 3.22 3.97 3.90 5.50
0/TBAc
— — — — — — 4.56 — 4.90x — — — 3.79 3.89 — — — — — 4.43 — — 5.36 — — 3.84w — 3.19wx 3.42wx — 3.53w
E 2/TBAd
TBA/0e
TBA/TBAf
TBA x 342
— 3.67 — 3.90 — — — — — 3.81 3.76 — 2.69wx — — — 4.06xw 3.35wx 3.39wx
5.37 3.31 4.23 — 5.98 3.25 4.29 4.85x 2.35 — 3.82 3.91x — 4.20 5.76 3.56 — 3.51x 2.92x
— 3.40 — 3.71 — — — — — 3.81 3.87 — 3.01y — 5.37 3.55 4.15x 3.27wx 3.18x
— — — — — — — — — — — 2.89xy — — — — — —
aSex
of animals in trial: s = steers, h = heifers, and cc = cull cows. estradiol (E2)-only treatment. cInitial implant was none, and re-implant was a trenbolone acetate (TBA) treatment. dInitial implant was estradiol, and re-implant was a TBA treatment. eInitial implant was a TBA treatment, and there was no re-implant. fInitial implant and re-implant were TBA treatments. gAverage WBS values for three cuts of meat: strip loin, top sirloin, and top round. hControl vs all implants (P<0.05); control vs TBA (P<0.10). w,x,yMeans within a row with different superscripts differ (P<0.05). bAny
implantation with TBA/E2 were intermediate and not different than steaks from the NI steers (3.52, 3.33, 3.38, and 3.48 kg, respectively). Hunt et al. (18) reported that implants improved tenderness in bulls as measured by WBS, whereas there was no significant difference with the same implant in steers (NI = 3.40, TBA = 3.30, and TBA/E2 = 3.20 kg for steers, respectively). In a review article by Morgan (35), steaks from I cattle had a 0.49 kg higher WBS than steaks from NI cattle. The NI cattle had an average WBS of 3.62 kg. Adding the average increase (0.49 kg) in shear force resulting from implants would yield a WBS for steaks from I cattle of 4.13 kg, which is still in the “tender” category. However, Morgan (35) did
not provide statistical information, so it is unclear whether the 0.49-kg increase reported with implants was statistically significant. Similarly, Duckett et al. (10) reviewed 29 trials with regard to WBS means of I and NI cattle. Overall, no differences (P=0.79) were noted between WBS for I and NI cattle. The overall mean change in WBS for NI vs all I strategies was 0.26 kg, which did not differ statistically. Of the 29 studies evaluated, only five comparisons consisting of two types E2, TBA/E2, E2/TBA, or E2/TBA followed by TBA implants had increased (P<0.05) WBS compared with that of NI steers. Duckett et al. (10) further stated that their review illustrated the lack of evidence to suggest any detrimental effects of implanting on beef tenderness or
marbling. Similarly, Belk and Cross (3) found that only two E2 steroid implant treatments from 1 of 16 studies they examined negatively affected beef tenderness. Belk and Cross (3) concluded that there was no consistent pattern with respect to the effects of implants on beef tenderness. One problem with addressing the effects of steroids on tenderness of beef is the inconsistency between and within trials. For example, Roeber et al. (45) evaluated eight different implant combinations using 298 finishing beef steers. The only implant regimen that increased (P<0.05) WBS over that of the NI cattle was the use of TBA/E2 as the initial implant with no re-implantation (3.51 vs 2.97 kg). However, the
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use of TBA/E2 as the initial implant followed by TBA/E2 at re-implantation and a high dose of TBA/E2 implant as the initial with no reimplantation did not statistically affect WBS relative to NI steers (3.27, 3.28, and 2.97 kg, respectively). If the effects of implants on growth are related to tenderness, then one might hypothesize that implant strategies that produce more rapid gains would have the most negative effects on tenderness, which was not the case in these data. Kerth et al (25) demonstrated that steaks from heifers that were re-implanted with TBA/E2 in succession were more tender, as measured by WBS, than steaks from NI heifers. Therefore, as these data demonstrate that the implant dose response relationship with respect to WBS values is unknown and may not exist. When comparing the difference in WBS of steaks from I and NI cattle, it is important to note that tenderness is a threshold value, with the cut-off for tender vs tough at 4.54 kg. In most of the studies we reviewed (2, 11, 31, 34, 36, 43, 44, 45, 56), no differences were found as a result of implant strategy in the percentage of steaks that would be classified as tough. For example, in the study by Foutz et al. (11), in which differences in average WBS values between steaks from I and NI steers were noted, no differences were found in the percentage of tender steaks between these groups. Similarly, Nichols et al. (36) reported that steaks from NI cattle had a lower WBS value, but the percentage of tender steaks did not differ between I and NI cattle. Tenderness Measured by Taste Panels. Data from trials that measured tenderness using a sensory taste panel are shown in Table 2. Thirteen studies that met the criteria to be included in the review included sensory panel tenderness evaluations. Three of the 13 sensory panels found that steroid implants decreased the tenderness of steaks from I cattle relative to steaks from NI cattle (36, 45, 53). One study demonstrated an improvement in taste panel tender-
Nichols et al.
ness for I beef compared with NI beef (6). Roeber et al. (45) found that all implant treatments containing a TBA/E2 implant decreased tenderness; however, no significant differences were noted in flavor, flavor intensity, juiciness level, and perhaps most importantly like/dislike in steaks from I compared with NI steers. Thonney et al. (53) reported similar findings. Nichols et al. (36) reported that steaks from heifers implanted with TBA/E2 were less tender than steaks from the NI cattle. However, their study also showed that steaks from heifers implanted with TBA only and fed MGA were similar in sensory panel tenderness evaluation to steaks from NI heifers. In contrast, Cranwell et al (6) found that implanting cull cows with TBA only, TBA/E2, or E2 improved tenderness compared with NI cull cows. Although effects on tenderness have been noted in some taste panel evaluations, a clear effect of implants on overall acceptability of steaks from I cattle has not been demonstrated. The remaining nine studies that met the criteria to be included in this review showed no evidence that sensory panel tenderness evaluation differed between I and NI cattle (1, 7, 17, 18, 24, 25, 39, 53, 56). As with WBS, in the studies that measured overall like/dislike, overall palatability, or overall acceptability, none reported a significant difference between I cattle and NI cattle (1, 7, 24, 39, 53, 56). Removing genetic variation within a trial might be one means of obtaining a more precise estimate of the effects of implants on tenderness. The use of genetically identical animals (clones) might be one way of removing genetic variation to some degree. Gerken et al. (13), using cloned steers, found little difference in steak sensory panel tenderness evaluations among steers in NI, E2only, TBA-only, or TBA/E2 treatments. There were no differences in tenderness values for cuts from the strip loin or top round; however, the use of an E2 implant decreased the tenderness of steaks from the top
sirloin relative to NI cattle. These results tend to agree with those of Roeber et al. (45), in that the lower potency implant strategy had more effect on tenderness than an aggressive implant strategy. Calpain and Calpastatin. As noted previously, the measurement of endogenous proteases has been used recently to evaluate potential effects on beef tenderness. Calpain is a protease that has been associated with increasing the hydrolysis of myofibrillar proteins, which in turn might increase the tenderness of beef. Calpastatin is an inhibitor of calpain. Therefore, high levels of calpain should indicate that a muscle has more potential to yield a tender steak, whereas high levels of calpastatin should indicate that a muscle has more potential to be tough. Gerken et al. (13) found that steroid implants (Table 3) did not affect the activity of m- or µ-calpain in fresh LD relative to NI beef. However, muscles from steers implanted with TBA/E2 or E2 had higher (P<0.05) activity levels of calpastatin than muscles from NI steers. There was no difference in calpastatin activity level between muscles from the NI steers or steers implanted with TBA. Presumably because the differences in calpastatin activity levels were not of sufficient magnitude to affect either of the calpain postmortem activities, the authors suggested that these changes in calpastatin activity were probably not associated with differences in beef tenderness. Kerth et al. (24) reported that muscles from steers implanted with a high dose of TBA/E2 did not differ in m- or µ-calpain activity (Table 3) relative to muscles from the NI steers. In contrast to the study by Gerken et al. (13), Kerth et al. (24) found that muscles from NI steers had significantly higher levels of calpastatin activity than muscles from the steers implanted with TBA/E2. Although limited in scope, data from these two trials suggest that implanting cattle with steroids has little or no effect on
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TABLE 2. Summary of published experiments that have evaluated the effects of steroid implants on sensory taste panel evaluation of tenderness. Reference
Crouse et al.g Trenkleg Apple et al.g Huffman et al.g Hunt et al.g Perry et al.g Thonney et al.g Gerken et al.g,h Cranwell et al.g Kerth et al.i Nichols et al.g Roeber et al.i Kerth et al.i
Year
1987 1990 1991 1991 1991 1991 1991 1995 1996 1996 1996 2000 2002
Animals (no.) 77 300 72 46 30 72 64 24 60 12 600 298 320
Sexa
Control
h s s s s s s s cc s h s h
5.35 6.70 6.50 5.10 6.10 6.26 5.84x 4.30 5.20y 6.10 5.96x 3.90x 5.80
E2 b
5.70 6.35 5.20
4.03 5.50x 4.25xy
0/TBAc
E 2/TBAd
TBA/0e
TBA/TBAf
— — — — — — — — — — — 4.48y 6.00
— 5.40 — — — — — — — — — 4.49y 5.60
5.32 6.00 6.23 5.00 6.05 6.12 5.19y 4.32 5.60x 6.10 5.78y 4.49y 6.00
— 5.60 — — — — — — — — — 4.53y 6.00
aSex
of animals in trial: h = heifers, s = steers, and cc = culled cows. estradiol (E2)-only treatment. cInitial implant was none, and re-implant was a trenbolone acetate (TBA) treatment. dInitial implant was estradiol, and re-implant was a TBA treatment. eInitial implant was a TBA, and there was no re-implant. fInitial implant and reimplant were TBA treatments. g1 = Extremely tough to 8 = extremely tender. hControl vs E (P<0.05) for top sirloin only. 2 i1 = Extremely tender to 9 = extremely tough. x,yMeans within a row with different superscripts differ (P<0.05). bAny
m- or µ-calpain activity. Moreover, the effects of steroids on calpastatin activity are not clear because the two trials had opposite results with respect to the effects of implants. Neither group of researchers considered the calpastatin activity between beef from I nor NI steers to be sufficient to decrease tenderness. Summary and Conclusions. It is clear from this review that the doseresponse surface for the effects of implants on beef tenderness is not defined. The trials summarized in this review do not indicate a clear response as to the effects of increasing implant potency (with respect to growth promotion) having a greater or more consistent effect on tenderness. It seems plausible that if implants have a negative effect on beef tenderness, the more aggressive implant strategies would amplify this effect; however current data do not support this hypothesis. Three of the
19 papers we reviewed indicated that steaks from I cattle had higher WBS values than steaks from NI cattle, and three of the 13 studies using taste panel evaluations found that implants decreased the tenderness of beef. Two of the studies found an increase in beef tenderness with I cattle as measured by WBS, and one study demonstrated an improvement in tenderness with beef from I cattle as measured by sensory taste panels. None of these studies reported a difference in overall taste panel acceptability of the beef steaks analyzed. Furthermore, no study demonstrated that all implant strategies in a particular experiment negatively affected either WBS or sensory taste panel evaluations. We interpret both the WBS and sensory taste panel results to suggest that the currently available growth-promoting implants have limited, if any, effects on tenderness of beef. To receive
approval for sale and use of implants to increase ADG and improve feed efficiency in feedlot cattle or to increase ADG by pasture cattle, the safety and efficacy of implants must be documented to the federal U.S. Food and Drug Administration. This response is measurable and repeatable. The trials reviewed herein do not establish this same level of consistency or repeatability with respect to the effects of implants on beef tenderness and palatability. As noted previously, implants increase the mature BW of cattle and shift the growth curve higher than in NI cattle. It might be expected that if implants decrease tenderness, beef from larger-framed cattle with heavier final BW at physiological maturity also might be less tender than beef from a smaller-framed animal that would finish at a lighter BW. This should also be true of cattle within the same breed. The effect of frame-
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TABLE 3. Effects of steroid implants on m-calpain, m-calpain, and calpastatin activity in muscles of cattle. Reference
Item
Control
TBA/E2a
Gerken et al.
m-calpain, unit/g µ-calpain, unit/g calpastatin, unit/g m-calpain, unit/g µ-calpain, unit/g calpastatin, unit/g
0.51 0.71 2.90x 0.90 0.97 1.86x
0.49 0.67 3.35y 0.65 0.76 1.20y
Kerth et al.
aTBA
= Trenbolone acetate; E2 = estradiol. in a row with different superscripts differ (P<0.05).
x,yMeans
size or BW at physiological maturity on beef tenderness has not been thoroughly investigated and warrants further study.
Literature Cited
8. Dayton, W. R., B. J. Johnson, M. E. White, and M. R. Hathaway. 1999. Effect of anabolic steroid implantation on muscle growth in feedlot steers. In Minnesota Feeders Day Rep. p 1. Dep. Anim. Sci., Univ. of Minnesota, St. Paul, MN. 9. Doane Marketing Research, Inc. 2001. Shaker Heights, OH. Doane Marketing Research, Inc., Marketing Report: Implant Utilization. 10. Duckett, S. K., D. G. Wagner, F. N. Owens, H. G. Dolezal and D. R. Gill. 1996. Effects of estrogenic and androgenic implants on performance, carcass traits and meat tenderness in feedlot steers: A review. Prof. Anim. Sci. 12:205. 11. Foutz, C. P., H. G. Dolezal, T. L. Gardner, D. R. Gill, J. L. Hensley, and J. B. Morgan. 1997. Anabolic implant effects on steer performance, carcass traits, subprimal yields and longissmus muscle properties. J. Anim. Sci. 75:1256. 12. Galyean, M. L. 1996. Protein levels in beef finishing diets: Industry application, university research, and systems results. J. Anim. Sci. 74:2860.
Implications The use of anabolic implants has proven in a number of well-conducted trials to improve growth and growth efficiency in all phases of beef cattle production. These improvements in production, ultimately improves profitability for those in the beef cattle industry. This review of the current data suggests that the effects of implants on beef tenderness, as measured by WBS and tastepanel tenderness evaluations has been negligible when detected, and most of the studies reviewed did not detect any deleterious effects. The dose response surface of implants on beef tenderness has not been defined and warrants further study. Such studies should be designed so that all treatments are tested at equal physiological maturities. This type of design would allow for an accurate test of the dose response surface or effect of implants on tenderness of beef, without the potential confounding effects of differences in marbling, age, or physiological maturity.
7. Crouse, J. D., B. D. Schanbacher, H. R. Cross, S. C. Seideman, and S. B. Smith. 1987. Growth and carcass traits of heifers as affected by hormonal treatment. J. Anim. Sci. 64:1434.
1. Apple, J. K., M. E. Dikeman, D. D. Simms, and G. Kuhl. 1991. Effects of synthetic hormone implants, singularly or in combinations, on performance, carcass traits, and longissmus muscle palatability of Holstein steers. J. Anim. Sci. 69:4437.
13. Gerken, C. L., J. D. Tatum, J. B. Morgan, and G. C. Smith. 1995. Use of genetically identical (clone) steers to determine the effects of estrogenic and androgenic implants on beef quality and palatability characteristics. J. Anim. Sci. 73:3317.
2. Beirman, S. J., R. H. Pritchard, and R. T. Brandt. 1999. Influences of delaying initial implant or re-implant date on production characteristics and carcass traits of steers fed high grain content diets. J. Anim. Sci. 77(Suppl. 1):77(Abs.).
14. Hayden, J. M., W. G. Bergen, and R. A. Merkel. 1992. Skeletal muscle protein and serum somatotropin, insulin, cortisol concentrations in growing steers implanted with estradiol-17β, trenbolone acetate or estradiol-17β plus trenbolone acetate. J. Anim. Sci. 70:2109.
3. Belk, K. E., and H. R. Cross. 1988. Effects of anabolic growth promotants on beef carcass merit. In A Review from the Meats and Muscle Biology Section. p 1. Dep. Anim. Sci., Texas A&M Univ., College Station, TX. 4. Brier, B. H., P. D. Gluckman, and J. J. Bass. 1988. The somatotrophic axis in young steers: influence of nutritional status and estradiol-17 beta on hepatic high-and-low affinity somatotrophic binding sites. J. Endocrinol. 116:169. 5. Bruns, K. W., and R. H. Pritchard. 2001. The effect of anabolic implant use on Allometeric growth and carcass composition of steer calves. In Plains Nutr. Council. Pub. No. AREC 01-23. Texas A&M Res. and Ext. Center, Amarillo, TX.
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17. Huffman, R. D., R. L. West, D. L. Pritchard, R. S. Sand, and D. D. Johnson. 1991. Effect of Finaplix and Synovex implantation on feedlot performance and carcass traits. In Florida Beef Cattle Res. Rep. 91. p 45. Anim. Sci. Dept., Univ. Florida, 6. Cranwell, C. D., J. A. Unruh, J. R. Brethour, Gainsville, FL. and D. D. Simms. 1996. Influence of steroid implants and concentrate feeding on carcass 18. Hunt, D. W., D. M. Henricks, G. C. and longissmus muscle sensory and collagen Skelley, and L. W. Grimes. 1991. Use of characteristics of cull beef cows. J. Anim. Sci. trenbolone acetate and estradiol in intact and 74:1777.
REVIEW: Steroid Implants and Beef Tenderness
castrate male cattle: Effects on growth, serum hormones, and carcass characteristics. J. Anim. Sci. 69:2452. 19. Hutcheson, J. P, D. E. Johnson, C. L. Gerken, J. B. Morgan, and J. D. Tatum. 1997. Anabolic implant effects on visceral organ mass, chemical body composition, and estimated energetic efficiency in cloned (genetically identical) beef steers. J. Anim. Sci. 75:2620. 20. Johnson, B. A., M. R. Hathaway, P. T. Anderson, J. C. Mieske, and W. R. Dayton. 1996. Stimulation of circulating insulin-like growth factor-I (IGF-I) and insulin-like growth factor binding proteins (IGFBP) due to administration of a combined trenbolone acetate and estradiol implant in feedlot cattle. J. Anim. Sci. 74:372. 21. Johnson, B. J., P. T. Anderson, J. C. Meiske, and W. R. Dayton. 1996. Effects of a combined trenbolone acetate and estradiol implant on feedlot performance, carcass characteristics, and carcass composition of feedlot steers. J. Anim. Sci. 74:363. 22. Johnson, B. J., N. Halstead, M. E. White, M. R. Hathaway, and W. R. Dayton. 1998. Activation state of muscle satellite cells isolated from steers implanted with a combined trenbolone acetate and estradiol implant. J. Anim. Sci. 76:2779. 23. Johnson, B. J., M. E. White, M. R. Hathaway, C. J. Christians, and W. R. Dayton. 1998. Effect of a combined trenbolone acetate and estradiol implant on steady-state IGF-1 mRNA concentrations in the liver of wethers and the longissimus muscle of steers. J. Anim. Sci. 76:491. 24. Kerth, C. R., M. A. Carr, M. F. Miller, D. U. Thomson, R. L. Preston, and C. S. Whisnant. 1995. Short term effects of implants on carcass characteristics, sensory traits, shear values, and the calcium-dependent protease system. In Texas Tech University Res. Rep. T5-356:x. Texas Tech Univ., Lubbock, TX. 25. Kerth, C. R., J. L. Montgomery, K. J. Morrow, M. L. Galyean, and M. F. Miller. 2001. Protein turnover and sensory traits of longissimus muscle from implanted and nonimplanted heifers. J. Anim. Sci. (Submitted). 26. Kineman, R. D., W. J. Faught, and L. S. Frawley. 1991. Mammosomatotropes are abundant in bovine pituitaries: Influence of gonadal status. Endocrinology 128:2229. 27. Kreig, M. 1976. Characterization of the androgen receptor in the skeletal muscle of rats. Steroids 28:261. 28. Kuhl, G. 1997. Carryover and lifetime effects of growth promoting implants. Synposium: Impact of implants on performance and carcass value of beef cattle. In Oklahoma Agric. Exp. Stn. P-957. p 51. Oklahoma State Univ., Stillwater, OK. 29. Loy, D. D., H. W. Harpster, and E. H. Cash. 1988. Rate, composition, and efficiency of growth in feedlot steers reimplanted with growth stimulants. J. Anim. Sci. 66:2668.
30. Mader, T. 1997. Carryover and lifetime effects of growth promoting implants. Synposium: Impact of implants on performance and carcass value of beef cattle. In Oklahoma Agric. Exp. Stn. P-957. p 88. Oklahoma State Univ., Stillwater, OK. 31. Martinez-Peraza, M. J., K. E. Belk, J. D. Tatum, and G. C. Smith. 1999. Effects of age at castration, implant strategy and aging on the tenderness of longissmus muscle steaks derived from steers, late castrates, and intact bulls. In Beef Program Report. p 135. Colorado State Univ., Ft. Collins, CO. 32. Meyer, H.H.D., and M. Rapp. 1985. Reversible binding of anabolic steroid trenbolone to steroid receptors. Acta Endocrin. 108(267):129. 33. Milton, C. T., R. T. Brandt, Jr., G. L. Kuhl, and P. T. Anderson. 1996. Implant strategies for finishing calves. In Kansas State University, Cattleman’s Day. p 108. Kansas State Univ., Manhattan, KS. 34. Milton, C. T., and D. Horton. 2000. Evaluation of Various Implant Programs for Finishing Steers on Performance, Carcass Merit and Beef Tenderness. Revalor-IS Technical Reference 1. Intervet, Inc, Millsboro, DE. 35. Morgan, J. B. 1997. Implant program effects on USDA beef carcass quality grade traits and meat tenderness. Symposium: Impact of implants on performance and carcass value of beef cattle. In Oklahoma Agric. Exp. Stn. P-957. p 147. Oklahoma State Univ., Stillwater, OK. 36. Nichols, W. T., M. I. Wray, T. H. Montgomery, B. Schutte, J. B. Morgan, H. G. Dolezal, and D. P. Hutcheson. 1996. The effects of anabolic agents alone and in combination on feedyard performance, carcass characteristics and meat quality of finishing heifers fed for 108, 131 or 143 days. In Revalor-H, Technical Bulletin 3. p 1. Hoechst-Roussel Agri-Vet., Co, Summerville, NJ. 37. Nichols, W. T., D. P. Hutcheson, F. M. Byers, W. L. Meis, and T. R. Kasari. 1991. Effects of anabolic growth promotants on rate and composition of growth in finishing beef steers. Ph.D. Dissertation. Texas A&M Univ., College Station, TX. 38. Owens, F. N., J. Hill, and C. Hanson. 1996. New management approaches to alter mature body size and body composition. In Composition of Growth of Beef Cattle. p 49. Elsevier Pub., Essex, England. 39. Perry, T. C., D. G. Fox, and D. H. Beerman. 1991. Effect of an implant of trenbolone acetate and estradiol on growth, feed efficiency, and carcass composition of Holstein and beef steers. J. Anim. Sci. 69:4696. 40. Preston, R. L. 1978. Possible role of DES on mature size of steers. J. Anim. Sci. 47(Suppl. 1):436. 41. Preston, R. L. 1987. Role of anabolic and repartitioning agents in the production of lean beef. In Univ. Arizona, Southwest Nutr
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and Mgmt Conf. Proc. p 12. Univ. Arizona, Tucson, AZ. 42. Preston, R. L., D. U. Thomson, R. Grant, and W. T. Nichols. 1996. Trenbolone acetate and estradiol dose titration study in feedlot steers. Texas Tech Univ. Res. Rep. T-5-447. Texas Tech Univ., Lubbock, TX. 43. Pritchard, R. H., K. W. Bruns, and C. P. Birkelo. 2000. A comparison of lifetime implant strategies on production and carcass characteristics in steers. J. Anim. Sci. 78(Suppl. 1):195(Abs.). 44. Pruneda, I., C. W. Walenciak, B. A. Gardner, H. G. Dolezal, F. N. Owens, and B. Freking. 1999. Time of implanting prior to harvest effects on meat tenderness. In Oklahoma State University Anim. Sci. Res. Rep. p 165. Oklahoma State University, Stillwater, OK. 45. Roeber, D. L, R. C. Cannell, K. E. Belk, R. K. Miller, J. D. Tatum, and G. C. Smith. 2000. Implant strategies during feeding: Impact on carcass and consumer acceptability. In Colorado State Univ. Anim Sci. Res. Rep. p 9. Colorado State Univ., Fort Collins, CO. 46. Roeder, R. A., S. D. Thorpe, F. M. Byers, G. T. Schelling, and J. M. Gunn. 1986. Influence of anabolic agents on protein synthesis and degradation in muscle cells grown in culture. Growth 50:485. 47. Samber, J. A., J. D. Tatum, M. I. Wray, W. T. Nichols, J. B. Morgan, and G. C. Smith. 1996. Implant program effects on performance and carcass quality of steer calves finished for 212 days. J. Anim. Sci. 74:1470. 48. Selk, G. 1997. Carryover and lifetime effects of growth promoting implants. Symposium: Impact of implants on performance and carcass value of beef cattle. In Oklahoma Agric. Exp. Stn. P-957. p 40. Oklahoma State Univ., Stillwater, OK. 49. Snochowski, M. K., K. Lundstrom, E. Dahlberd, and H. Peterson. 1981. Androgen and glucocorticoid receptors in porcine skeletal muscle. J. Anim. Sci. 53:80. 50. Thomson, D. U., C. S. Whisnant, R. L. Preston, M. F. Miller, M. A. Carr, and C. R. Kerth. 1995. Short term effect of trenbolone acetate and estradiol on finishing steers: Anterior pituitary cell transformation in finishing beef steers. Texas Tech Univ. Agric. Sci. Nat. Res. Tech. Rep. T-5-316. p 11. Texas Tech University, Lubbock, TX. 51. Thomson, D. U., R. L. Preston, and K. L. Morrow. 1996. Direct effects of cholesterol, trenbolone acetate, estradiol and progesterone on beef muscle cell protein synthesis. In Texas Tech Univ. Agric. Sci. Nat. Res. Tech. Rep. T-5-316. p 16. Texas Tech University, Lubbock, TX. 52. Thomson, D. U., R. L. Preston, and K. L. Morrow. 1996. Effect of serum from steers treated with a steroidal implant and somatotropin alone and in combination on in vitro muscle cell proliferation, protein synthesis and degradation. In Texas Tech Univ. Agric. Sci. Nat. Res. Tech. Rep. T-5-316. p 13. Texas Tech University, Lubbock, TX.
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53. Thonney, M. L., T. C. Perry, G. Armbruster, D. H. Beerman, and D. G. Fox. 1991. Comparison of steaks from Holstein and Simmental × Angus steers. J. Anim. Sci. 69:4866 54. Trenkle, A. 1983. Mechanisms of action for the use of anabolics in animals. In Anabolics in Animal Production. E. Meissonnier (Ed.). p 65. Plenum Press, New York, NY.
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55. Trenkle, A. 1970. Plasma levels of somatotropin, insulin and plasma proteinbound iodine in finishing cattle. J. Anim. Sci. 31:389. 56. Trenkle, A. 1990. The evaluation of Synovex S, Synovex S – Finaplix S, and Revalor S implant programs in feedlot steers. In Iowa State Univ. Beef-Sheep Res. Rep. AS606:56. Iowa State University, Ames, IA.
57. Trenkle, A. 1990. Impact of implant strategies on performance and carcass merit of feedlot cattle. In Univ. Arizona Southwest Nutr. Mgmt. Conf. Proc. p 13. Univ. Arizona, Tucson, AZ.
The Professional Animal Scientist Nichols et al. 18 (2002):202–210
: Effects of Steroid RImplants on the EVIEW
Tenderness of Beef W. T. NICHOLS*,1 , PAS, M. L. GALYEAN†, PAS, D. U. THOMSON‡, PAS, and J. P. HUTCHESON* *Intervet, Inc., Millsboro, DE 19966, †Department of Animal and Food Sciences, Texas Tech University, Lubbock, TX 79409, and ‡Cactus Feeders, Inc., Amarillo, TX 79116
Abstract
weight restrictions, and so on. By understanding how steroid implants All cattle in the suckling through work, coupled with knowledge of growth finishing phases of production respond to physiology, cattle genetics, and the implants. In feedlot cattle, implants market, a producer can use these tools to have been reported to improve ADG by fit many different feeding and economic 15 to 25% and feed efficiency by 10 to scenarios. There has been concern in the 15%. The resulting increase in saleable industry that androgenic implants, used carcass and the associated benefits in feed alone or in combination with estrogenic efficiency make a regular, systematic implants, might decrease marbling or implant program profitable for the affect other palatability factors. Based producer. Recent research with anabolic on the data we reviewed, the currently steroid implants has demonstrated that available growth-promoting implants growth occurs normally as a result of have limited, if any, effects on tenderness concomitant increases in bone, muscle, of beef as determined by Warnerand fat, with proportions of these compo- Bratzler shear force (WBS) or taste panel nents staying relatively the same, but evaluation of tenderness. Further increased absolute amounts being research should be conducted to evaluate deposited. In addition, feeding implanted the effects of growth-promoting implants (I) cattle longer so that they may reach on calpain and calpastatin activities in physiological endpoint has been shown to muscle. compensate for decreased marbling, allowing I cattle to grade similarly to (Key Words: Beef, Tenderness, non-implanted (NI) cattle. Nonetheless, I Implants, Carcass, Steroid.) cattle would be heavier at the same physiological endpoint, which could have both positive and negative effects on Estrogenic and androgenic steroids marketing schemes. The producer can have been used for the last halfadjust implant strategies to fit variable century to enhance the efficiency of market conditions, including high vs low beef production. Since 1954, many diet costs, live BW restrictions, carcass different combinations of dosages and ratios of estrogen with other steroids have been approved for use in confined and pastured beef cattle. 1To whom correspondence should be adSteroid implants are the best availdressed: [email protected] able non-nutritional management
Introduction
tools for a producer to increase biological and economical efficiency of beef cattle (41). The efficient production of safe, wholesome, and palatable beef products might well determine the future of the beef industry. Production efficiency can be defined as the return of saleable product per unit of feed input; however, composition of the product is an increasingly important factor in determining the product unit value and cost. Although final weights are significantly different, recent research indicates that the percentage of protein, adipose, and bone is similar in implanted (I) and non-implanted (NI) animals when finished to the same physiological end point (5, 19, 37). The mechanisms involved in this increase in the growth curve of I cattle include modification of priorities for nutrient use for protein vs fat deposition, alteration of tissue turnover, modification of daily tissue deposition limits, and modification of nutrient supply (19, 37, 54). Recently, tenderness and palatability of beef products have been recognized as potentially important issues affecting the beef industry. The palatability of beef products is related to flavor, juiciness, and tenderness. Marbling is an important component of flavor and juiciness, and, because growthpromoting implants enhance both
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both I and NI cattle consume enough energy to maximize fat accretion rates; hence, implants would not be expected to affect fat accretion markedly. Anabolic implants that contain estrogens, androgens, or a combination of the two do not have a direct lipolytic effect on adipose tissue. At equal physiological maturity, carcass composition will be similar between I (TBA/E2, TBA, or E2) and NI cattle (19, 37). Loy et al. (29) and Preston (40) showed that steroid implants containing estrogens increased the mature body size of steers. Both small- and large-framed steers that were implanted regularly with estrogenic steroids had increased BW gains, hip heights (40), and BW:height ratios compared with NI steers. Preston (40) fed cattle for up to 486 d, and the NI steers never equaled the I steers for hip height, indicating that estrogenic implants increase mature body size. Roeder et al. (46) reported that anabolic steroids do not directly stimulate protein synthesis in rat muscle cells, and Thomson et al. (52) found the same to be true for beef muscle cells cultured in vitro and treated directly with estradiol-17ß (E2), TBA alone, or the combination. Thomson et al. (51) treated fetal Mechanism of Action of Steroids. muscle cells with serum from steers Steroid implants increase protein implanted with TBA:E2 and bovine somatotropin (bST) alone and in synthesis and decrease protein combination. Steroids indirectly degradation. Johnson et al. (21) increased protein synthesis, with no reported that I steers [trenbolone acetate (TBA)/estradiol (E2) vs NI] had effect on protein degradation, which increased protein and bone deposiagrees with the in vivo effects of E2 and TBA on protein turnover retion relative to NI steers. Moreover, ported by Hayden et al. (14). carcass water was greater in I steers The anabolic response of rumibecause water is deposited with nants to androgens and estrogens, in protein. Johnson et al. (21) also addition to the direct effects noted reported that the anabolic implant had no effect on carcass fat accretion previously, might result from indirect actions (e.g., alterations in blood during the feeding period. At the concentrations of growth factors end of the feeding period, NI steers had decreased fat deposition, whereas such as growth hormone or soI cattle were continuing to deposit fat matomedins). Several studies have indicated that estrogens stimulate at a linear rate, indicating that the growth hormone secretion (8, 18, 54) NI cattle had reached physiological and growth hormone receptor maturity sooner than the I cattle. numbers in the liver (4). Because the Owens (38) suggested that cattle have a maximum limit for fat deposi- liver also is a primary source of somatomedins, an estrogenic stimution. During the finishing phase,
lus might ultimately increase somatomedin concentrations. Direct effects of implants via specific receptors in muscle tissue might also occur because androgen and estrogen receptors have been identified in the striated muscle of rats (27) and pigs (49), and estrogen receptors have been reported in cattle (32). Trenkle (55) reported that anabolic steroids increase the size of the pituitary and increase the number of acidophils. There are three types of acidophils located in the anterior pituitary: somatotropes [secrete growth hormone (GH)], lactotropes [secrete prolactin (PRL)], and mammosomatotropes (secrete GH and PRL). Thomson et al. (50) implanted steers 24 d before slaughter with TBA (200 mg):estradiol benzoate (28 mg). Anterior pituitaries were harvested at slaughter, and the reverse plaque assay (26) was used to examine the composition of the acidophils. Implanted steers had an increased percentage of somatotropes and a decreased percentage of mammosomatotropes relative to NI steers, but implanting had no effect on lactotropes. Implants increased the overall percentage of cells that secreted GH by 30% compared with NI steers. Therefore, TBA:E2 implants seem to be working, at least in part, through the GH pathway by increasing the size of the anterior pituitary and changing its composition by increasing the percentage of somatotropes. Some data suggest that both increased production of insulin-like growth factor-1 (IGF-I) and a higher number of actively proliferating (activated) muscle satellite cells might be involved in anabolic steroidinduced muscle growth (22, 23). Circulating concentrations of the potent anabolic growth factor IGF-I and steady-state hepatic IGF-I mRNA concentrations were significantly higher in steers implanted with a combination of TBA and E2 than in NI steers (20). Moreover, steady-state IGF-I mRNA concentrations in the longissimus (LD) of I steers were higher than in the corresponding
ADG and feed conversion, I cattle often have less marbling and lower quality grades than NI cattle when slaughtered on a time-constant basis (16, 28, 29, 30, 33, 39, 42, 48, 57). In contrast, more recent research has demonstrated that feeding I and NI cattle to equal physiological end points can alleviate these negative effects on marbling (5, 37). Therefore, flavor and juiciness have not been much of an issue because marbling seems to correlate well with these two variables (15); however, tenderness does not seem to correlate with the current quality standards for beef products. Because the issue of potential negative effects of steroid implants on beef tenderness has become a concern (45), the objective of this paper is to review the literature regarding the effects of steroid implants on the tenderness of beef. To understand the role that steroid implants might play in affecting tenderness, it is important to understand the mechanisms by which they might affect the growth physiology of cattle; thus, a brief review of the mechanism of action of steroid implants will be included.
Review and Discussion
204
muscle of NI steers. Thus, muscle tissue might produce higher concentrations of IGF-I in E2/TBA-treated steers (22). In addition, a greater number of actively proliferating satellite cells could be isolated from the semimembranosus muscle of I steers than from the corresponding muscle of NI steers (23). The ability of TBA/E2 to increase circulating and muscle IGF-I concentrations and to increase the number of activated satellite cells could play a critical role in anabolic steroid-induced muscle growth in beef cattle. Growth factors other than IGF-I, such as hepatocyte growth factor and fibroblast growth factor, also might be involved in anabolic steroid-induced muscle growth (8). How do these changes in metabolism that are responsible for increased growth in beef cattle relate to the effects of steroids on beef tenderness? The mechanism of action of steroid implants seems to be to increase protein and bone deposition through shifting the mature body size of cattle by increasing GH secretion, increasing IGF-I concentrations in the liver and muscle cells, increasing satellite cell proliferation, and so on. If implants decrease the tenderness of beef, is it also possible that largerframed, rapidly growing animals within a breed would differ in tenderness from smaller-framed animals in the same breed? Effects of frame size on beef tenderness do not seem to have been critically evaluated and might warrant further study. Effects of Implants on Tenderness. Beef tenderness is typically measured in one of two ways: 1) Warner Bratzler shear force (WBS) and 2) taste panel evaluation of tenderness. In addition, calpain and calpastatin activities in muscle tissue might be related to tenderness (13, 24). Our summary of the literature focused on WBS determinations and taste panel evaluations of tenderness. Limited data on muscle calpain and calpastatin activities were included to illustrate what is currently known about the effects of implants on these variables. Criteria used to
Nichols et al.
determine whether a study was included in this review were that the study must have included a NI control vs an I strategy in which at least one of the strategies used an implant that contained some level of TBA or a TBA implant treatment. A majority of the studies also included an estrogen-only implant treatment. These criteria were used because a majority of cattle receive a TBAcontaining implant sometime during the beef production period (9, 12). Treatments that included TBA were 1) no initial implant with a TBAcontaining implant as a final implant, 2) estrogen-only implant as the initial implant with a TBAcontaining implant as the final implant, 3) a TBA-containing implant as the initial implant with no final implant, and 4) a TBA-containing implant as both the initial and final implant. One trial was evaluated in which three implants were used, all of which contained TBA. Estrogen-only (E2) implants for this review included those that contained zeranol, Estradiol-17β, and estradiol benzoate without TBA. The TBA implants (or TBA treatments) included all implants or treatments that contained TBA. This would include TBA/E2 implants with both hormones in the same implant; TBAonly implants used in conjunction with an E2-only implant; TBA-only implants used in conjunction with melengestrol acetate (MGA), a progestin which increases endogenous estrogen through its action on the endocrine system; and TBA only. The control treatments in all studies did not receive any type of implant. Effects of Implants on WBS. Warner-Bratzler shear force has been used for many years as an index of beef tenderness. A WBS value of <3.85 kg is deemed to represent beef in the very tender category, values of 3.9 to 4.54 kg are considered tender, and a value of >4.54 kg is considered to represent tough beef (15, 35). The WBS comparisons for the published reports included in this review are shown in Table 1. There were 19 studies that met the criteria for
summarization. Three studies found a significant detrimental effect of one or more implant strategies on WBS (36, 45, 47), and two studies (25, 43) reported a positive effect of implants on WBS (lower score). Despite individual implant treatment differences from nonimplant treatments, there were no studies with multiple implant treatments in which a significant deleterious effect on WBS was noted with all implant treatments vs non-implant treatment. Samber et al. (47) reported that steaks from steers that had been implanted with TBA/E2 as the initial and the terminal implant (2X), or as the initial, intermediate, and the terminal implant (3X) had higher WBS values (P<0.05) than steaks from steers that were not implanted (2X = 3.00, 3X = 2.91, 3X = 3.00, NI = 2.58 kg, respectively). However, the WBS of steaks from steers that had an E2 implant initially, followed by a TBA/ E2 implant at time of re-implant did not differ from steaks of the control steers (2.63 and 2.58 kg, respectively). Similarly, steaks from steers implanted with two doses of E2 as the initial and intermediate implant, followed by a TBA/E2 as the terminal, or one dose of E2 as the initial and followed by two doses of TBA/E2 as the intermediate and terminal implant did not differ from steaks from NI steers (2.73, 2.74, and 2.58 kg, respectively). The authors reported that 91% of the loin steaks tested had WBS values <3.85 kg. Hence, the significance of these changes in WBS with implants to the consumer would likely be negligible. Kerth et al. (25) found that implanting heifers with TBA/E2 as the initial implant with no re-implant or TBA/ E2 as the initial implant and reimplanting with TBA/E2 decreased WBS, resulting in steaks with a lower WBS (P<0.05) than steaks from NI heifers (2.92, 3.17, and 3.48 kg, respectively). Steaks from all other implant strategies, not implanted initially and re-implantation withTBA/E2, a low dose of TBA/E2 initially and re-implantation with TBA/E2, and E2 initially and re-
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REVIEW: Steroid Implants and Beef Tenderness
TABLE 1. Summary of published experiments that have evaluated the effects of steroid implants on WarnerBratzler shear force (WBS) values (kg). Reference
Year
N
Crouse et al. Trenkle Apple et al. Huck et al. Huffman et al. Hunt et al. Gerken et al.g Cranwell et al. Kerth et al. Milton et al. Milton et al. Nichols et al. Samber et al. Foutz et al.h Beirman et al. Pruneda et al. Pritchard Roeber et al. Kerth et al.
1987 1990 1991 1991 1991 1991 1995 1996 1996 1996 1996 1996 1996 1997 1999 1999 2000 2000 2002
77 150 72 80 46 30 24 60 12 480 216 600 560 140 480 100 310 298 320
Sexa
Control
E2b
h s s s s s s cc s s s h s s s s s s h
5.45 2.86 4.01 3.68 4.82 3.40 4.16 5.10w 2.07 3.64 3.85 3.71w 2.58w 4.00 5.41 3.38 4.02x 2.97w 3.49w
— 3.22 3.97 3.90 5.50
0/TBAc
— — — — — — 4.56 — 4.90x — — — 3.79 3.89 — — — — — 4.43 — — 5.36 — — 3.84w — 3.19wx 3.42wx — 3.53w
E 2/TBAd
TBA/0e
TBA/TBAf
TBA x 342
— 3.67 — 3.90 — — — — — 3.81 3.76 — 2.69wx — — — 4.06xw 3.35wx 3.39wx
5.37 3.31 4.23 — 5.98 3.25 4.29 4.85x 2.35 — 3.82 3.91x — 4.20 5.76 3.56 — 3.51x 2.92x
— 3.40 — 3.71 — — — — — 3.81 3.87 — 3.01y — 5.37 3.55 4.15x 3.27wx 3.18x
— — — — — — — — — — — 2.89xy — — — — — —
aSex
of animals in trial: s = steers, h = heifers, and cc = cull cows. estradiol (E2)-only treatment. cInitial implant was none, and re-implant was a trenbolone acetate (TBA) treatment. dInitial implant was estradiol, and re-implant was a TBA treatment. eInitial implant was a TBA treatment, and there was no re-implant. fInitial implant and re-implant were TBA treatments. gAverage WBS values for three cuts of meat: strip loin, top sirloin, and top round. hControl vs all implants (P<0.05); control vs TBA (P<0.10). w,x,yMeans within a row with different superscripts differ (P<0.05). bAny
implantation with TBA/E2 were intermediate and not different than steaks from the NI steers (3.52, 3.33, 3.38, and 3.48 kg, respectively). Hunt et al. (18) reported that implants improved tenderness in bulls as measured by WBS, whereas there was no significant difference with the same implant in steers (NI = 3.40, TBA = 3.30, and TBA/E2 = 3.20 kg for steers, respectively). In a review article by Morgan (35), steaks from I cattle had a 0.49 kg higher WBS than steaks from NI cattle. The NI cattle had an average WBS of 3.62 kg. Adding the average increase (0.49 kg) in shear force resulting from implants would yield a WBS for steaks from I cattle of 4.13 kg, which is still in the “tender” category. However, Morgan (35) did
not provide statistical information, so it is unclear whether the 0.49-kg increase reported with implants was statistically significant. Similarly, Duckett et al. (10) reviewed 29 trials with regard to WBS means of I and NI cattle. Overall, no differences (P=0.79) were noted between WBS for I and NI cattle. The overall mean change in WBS for NI vs all I strategies was 0.26 kg, which did not differ statistically. Of the 29 studies evaluated, only five comparisons consisting of two types E2, TBA/E2, E2/TBA, or E2/TBA followed by TBA implants had increased (P<0.05) WBS compared with that of NI steers. Duckett et al. (10) further stated that their review illustrated the lack of evidence to suggest any detrimental effects of implanting on beef tenderness or
marbling. Similarly, Belk and Cross (3) found that only two E2 steroid implant treatments from 1 of 16 studies they examined negatively affected beef tenderness. Belk and Cross (3) concluded that there was no consistent pattern with respect to the effects of implants on beef tenderness. One problem with addressing the effects of steroids on tenderness of beef is the inconsistency between and within trials. For example, Roeber et al. (45) evaluated eight different implant combinations using 298 finishing beef steers. The only implant regimen that increased (P<0.05) WBS over that of the NI cattle was the use of TBA/E2 as the initial implant with no re-implantation (3.51 vs 2.97 kg). However, the
206
use of TBA/E2 as the initial implant followed by TBA/E2 at re-implantation and a high dose of TBA/E2 implant as the initial with no reimplantation did not statistically affect WBS relative to NI steers (3.27, 3.28, and 2.97 kg, respectively). If the effects of implants on growth are related to tenderness, then one might hypothesize that implant strategies that produce more rapid gains would have the most negative effects on tenderness, which was not the case in these data. Kerth et al (25) demonstrated that steaks from heifers that were re-implanted with TBA/E2 in succession were more tender, as measured by WBS, than steaks from NI heifers. Therefore, as these data demonstrate that the implant dose response relationship with respect to WBS values is unknown and may not exist. When comparing the difference in WBS of steaks from I and NI cattle, it is important to note that tenderness is a threshold value, with the cut-off for tender vs tough at 4.54 kg. In most of the studies we reviewed (2, 11, 31, 34, 36, 43, 44, 45, 56), no differences were found as a result of implant strategy in the percentage of steaks that would be classified as tough. For example, in the study by Foutz et al. (11), in which differences in average WBS values between steaks from I and NI steers were noted, no differences were found in the percentage of tender steaks between these groups. Similarly, Nichols et al. (36) reported that steaks from NI cattle had a lower WBS value, but the percentage of tender steaks did not differ between I and NI cattle. Tenderness Measured by Taste Panels. Data from trials that measured tenderness using a sensory taste panel are shown in Table 2. Thirteen studies that met the criteria to be included in the review included sensory panel tenderness evaluations. Three of the 13 sensory panels found that steroid implants decreased the tenderness of steaks from I cattle relative to steaks from NI cattle (36, 45, 53). One study demonstrated an improvement in taste panel tender-
Nichols et al.
ness for I beef compared with NI beef (6). Roeber et al. (45) found that all implant treatments containing a TBA/E2 implant decreased tenderness; however, no significant differences were noted in flavor, flavor intensity, juiciness level, and perhaps most importantly like/dislike in steaks from I compared with NI steers. Thonney et al. (53) reported similar findings. Nichols et al. (36) reported that steaks from heifers implanted with TBA/E2 were less tender than steaks from the NI cattle. However, their study also showed that steaks from heifers implanted with TBA only and fed MGA were similar in sensory panel tenderness evaluation to steaks from NI heifers. In contrast, Cranwell et al (6) found that implanting cull cows with TBA only, TBA/E2, or E2 improved tenderness compared with NI cull cows. Although effects on tenderness have been noted in some taste panel evaluations, a clear effect of implants on overall acceptability of steaks from I cattle has not been demonstrated. The remaining nine studies that met the criteria to be included in this review showed no evidence that sensory panel tenderness evaluation differed between I and NI cattle (1, 7, 17, 18, 24, 25, 39, 53, 56). As with WBS, in the studies that measured overall like/dislike, overall palatability, or overall acceptability, none reported a significant difference between I cattle and NI cattle (1, 7, 24, 39, 53, 56). Removing genetic variation within a trial might be one means of obtaining a more precise estimate of the effects of implants on tenderness. The use of genetically identical animals (clones) might be one way of removing genetic variation to some degree. Gerken et al. (13), using cloned steers, found little difference in steak sensory panel tenderness evaluations among steers in NI, E2only, TBA-only, or TBA/E2 treatments. There were no differences in tenderness values for cuts from the strip loin or top round; however, the use of an E2 implant decreased the tenderness of steaks from the top
sirloin relative to NI cattle. These results tend to agree with those of Roeber et al. (45), in that the lower potency implant strategy had more effect on tenderness than an aggressive implant strategy. Calpain and Calpastatin. As noted previously, the measurement of endogenous proteases has been used recently to evaluate potential effects on beef tenderness. Calpain is a protease that has been associated with increasing the hydrolysis of myofibrillar proteins, which in turn might increase the tenderness of beef. Calpastatin is an inhibitor of calpain. Therefore, high levels of calpain should indicate that a muscle has more potential to yield a tender steak, whereas high levels of calpastatin should indicate that a muscle has more potential to be tough. Gerken et al. (13) found that steroid implants (Table 3) did not affect the activity of m- or µ-calpain in fresh LD relative to NI beef. However, muscles from steers implanted with TBA/E2 or E2 had higher (P<0.05) activity levels of calpastatin than muscles from NI steers. There was no difference in calpastatin activity level between muscles from the NI steers or steers implanted with TBA. Presumably because the differences in calpastatin activity levels were not of sufficient magnitude to affect either of the calpain postmortem activities, the authors suggested that these changes in calpastatin activity were probably not associated with differences in beef tenderness. Kerth et al. (24) reported that muscles from steers implanted with a high dose of TBA/E2 did not differ in m- or µ-calpain activity (Table 3) relative to muscles from the NI steers. In contrast to the study by Gerken et al. (13), Kerth et al. (24) found that muscles from NI steers had significantly higher levels of calpastatin activity than muscles from the steers implanted with TBA/E2. Although limited in scope, data from these two trials suggest that implanting cattle with steroids has little or no effect on
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REVIEW: Steroid Implants and Beef Tenderness
TABLE 2. Summary of published experiments that have evaluated the effects of steroid implants on sensory taste panel evaluation of tenderness. Reference
Crouse et al.g Trenkleg Apple et al.g Huffman et al.g Hunt et al.g Perry et al.g Thonney et al.g Gerken et al.g,h Cranwell et al.g Kerth et al.i Nichols et al.g Roeber et al.i Kerth et al.i
Year
1987 1990 1991 1991 1991 1991 1991 1995 1996 1996 1996 2000 2002
Animals (no.) 77 300 72 46 30 72 64 24 60 12 600 298 320
Sexa
Control
h s s s s s s s cc s h s h
5.35 6.70 6.50 5.10 6.10 6.26 5.84x 4.30 5.20y 6.10 5.96x 3.90x 5.80
E2 b
5.70 6.35 5.20
4.03 5.50x 4.25xy
0/TBAc
E 2/TBAd
TBA/0e
TBA/TBAf
— — — — — — — — — — — 4.48y 6.00
— 5.40 — — — — — — — — — 4.49y 5.60
5.32 6.00 6.23 5.00 6.05 6.12 5.19y 4.32 5.60x 6.10 5.78y 4.49y 6.00
— 5.60 — — — — — — — — — 4.53y 6.00
aSex
of animals in trial: h = heifers, s = steers, and cc = culled cows. estradiol (E2)-only treatment. cInitial implant was none, and re-implant was a trenbolone acetate (TBA) treatment. dInitial implant was estradiol, and re-implant was a TBA treatment. eInitial implant was a TBA, and there was no re-implant. fInitial implant and reimplant were TBA treatments. g1 = Extremely tough to 8 = extremely tender. hControl vs E (P<0.05) for top sirloin only. 2 i1 = Extremely tender to 9 = extremely tough. x,yMeans within a row with different superscripts differ (P<0.05). bAny
m- or µ-calpain activity. Moreover, the effects of steroids on calpastatin activity are not clear because the two trials had opposite results with respect to the effects of implants. Neither group of researchers considered the calpastatin activity between beef from I nor NI steers to be sufficient to decrease tenderness. Summary and Conclusions. It is clear from this review that the doseresponse surface for the effects of implants on beef tenderness is not defined. The trials summarized in this review do not indicate a clear response as to the effects of increasing implant potency (with respect to growth promotion) having a greater or more consistent effect on tenderness. It seems plausible that if implants have a negative effect on beef tenderness, the more aggressive implant strategies would amplify this effect; however current data do not support this hypothesis. Three of the
19 papers we reviewed indicated that steaks from I cattle had higher WBS values than steaks from NI cattle, and three of the 13 studies using taste panel evaluations found that implants decreased the tenderness of beef. Two of the studies found an increase in beef tenderness with I cattle as measured by WBS, and one study demonstrated an improvement in tenderness with beef from I cattle as measured by sensory taste panels. None of these studies reported a difference in overall taste panel acceptability of the beef steaks analyzed. Furthermore, no study demonstrated that all implant strategies in a particular experiment negatively affected either WBS or sensory taste panel evaluations. We interpret both the WBS and sensory taste panel results to suggest that the currently available growth-promoting implants have limited, if any, effects on tenderness of beef. To receive
approval for sale and use of implants to increase ADG and improve feed efficiency in feedlot cattle or to increase ADG by pasture cattle, the safety and efficacy of implants must be documented to the federal U.S. Food and Drug Administration. This response is measurable and repeatable. The trials reviewed herein do not establish this same level of consistency or repeatability with respect to the effects of implants on beef tenderness and palatability. As noted previously, implants increase the mature BW of cattle and shift the growth curve higher than in NI cattle. It might be expected that if implants decrease tenderness, beef from larger-framed cattle with heavier final BW at physiological maturity also might be less tender than beef from a smaller-framed animal that would finish at a lighter BW. This should also be true of cattle within the same breed. The effect of frame-
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Nichols et al.
TABLE 3. Effects of steroid implants on m-calpain, m-calpain, and calpastatin activity in muscles of cattle. Reference
Item
Control
TBA/E2a
Gerken et al.
m-calpain, unit/g µ-calpain, unit/g calpastatin, unit/g m-calpain, unit/g µ-calpain, unit/g calpastatin, unit/g
0.51 0.71 2.90x 0.90 0.97 1.86x
0.49 0.67 3.35y 0.65 0.76 1.20y
Kerth et al.
aTBA
= Trenbolone acetate; E2 = estradiol. in a row with different superscripts differ (P<0.05).
x,yMeans
size or BW at physiological maturity on beef tenderness has not been thoroughly investigated and warrants further study.
Literature Cited
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Implications The use of anabolic implants has proven in a number of well-conducted trials to improve growth and growth efficiency in all phases of beef cattle production. These improvements in production, ultimately improves profitability for those in the beef cattle industry. This review of the current data suggests that the effects of implants on beef tenderness, as measured by WBS and tastepanel tenderness evaluations has been negligible when detected, and most of the studies reviewed did not detect any deleterious effects. The dose response surface of implants on beef tenderness has not been defined and warrants further study. Such studies should be designed so that all treatments are tested at equal physiological maturities. This type of design would allow for an accurate test of the dose response surface or effect of implants on tenderness of beef, without the potential confounding effects of differences in marbling, age, or physiological maturity.
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