Injection-site lesions: incidence, tissue histology, collagen concentration, and muscle tenderness in beef rounds

Cowman and G. C. SmithM. H. George, J. B. Morgan, R. D. Glock, J. D. Tatum, G. R. Schmidt, J. N. Sofos, G. L.

tenderness in beef roundsInjection-site lesions: incidence, tissue histology, collagen concentration, and muscle

1995, 73:3510-3518.J ANIM SCI

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3510

1To whom correspondence should be addressed.2Vet. Diagnostic Lab., Colorado State Univ., Fort Collins 80523.3National Cattlemen’s Association, 540 S. Quebec Street, Engle-

wood, CO 80155.Received April 3, 1995.Accepted August 17, 1995

Injection-Site Lesions: Incidence, Tissue Histology, Collagen Concentration,and Muscle Tenderness in Beef Rounds

M. H. George1, J. B. Morgan, R. D. Glock2, J. D. Tatum, G. R. Schmidt,J. N. Sofos, G. L. Cowman3, and G. C. Smith

Department of Animal Sciences, Colorado State University, Fort Collins 80523-1171

ABSTRACT: The national incidence and extent ofinjection-site lesions in the muscles of the round weredetermined via audits conducted at retail stores and inpurveying establishments. Two additional experi-ments were conducted to examine the subsequenteffects of pharmaceutical administration on tissuehistology, soluble and insoluble collagen concentra-tion, and muscle tenderness in beef bottom-rounds.Injection-site lesion incidence in beef round cutsaudited at retail (n = 3,538) and in steak-cuttingfacilities (n = 15,464) was 8.45 and 10.04%, respec-tively, with an average lesion-trim of 314.7 and 191.59g, respectively, in these two studies. Lesion classifica-tion revealed that 93.20 and 99.91% of lesionsreported for the retail and purveyor audits, respec-tively, were chronologically aged lesions. Overall,19,002 round cuts were examined, and injection-sitelesion incidence (nationally) was 9.74%, whereas

lesion-trim averaged 211.8 g. Warner-Bratzler shearmeasurements taken near lesions and in areas 7.62cm from the lesions were higher ( P < .001) forlesioned, than for control bottom-round steaks.Warner-Bratzler shear values for lesion cores were 3.5times greater than those in paired control (non-affected) steaks. Concentrations of insoluble andsoluble collagen were much higher ( P < .001) at thesite of the lesion center in lesion-afflicted vs controlsteaks. Histological determinations of the relativeproportions of muscle, connective tissue and fat to adistance of 5.08 cm from the site of the lesion centerconfirmed that severe disruption of muscle tissueconstituents and architecture had occurred. Injection-site lesions occur at an unacceptable frequency in themuscles of the round, and severe tissue changesaccompany these lesions that can dramatically affecttenderness of those cuts.

Key Words: Intramuscular Injection, Lesions, Beef, Incidence, Tenderness, Histology

J. Anim. Sci. 1995. 73:3510–3518

Introduction

Bovine Respiratory Disease Complex has beenestimated to cost the U.S. cattle industry between$600 and 700 million annually in death loss, reducedfeed efficiency, and therapeutic costs (Chirase, 1993;Furman, 1993). Moreover, Lambert (1991) in hispaper “Lost Opportunities In The Beef Industry,”estimated that in addition to stress and reducedperformance, multiple processing costs the beef indus-try in excess of $110 million annually. However, bothof these estimates fail to take into account subsequentcosts associated with tissue losses and reduced beef

tenderness resulting from the intramuscular injectionof biologicals and antimicrobials.

The National Beef Quality Audit−1991 (Smith etal., 1992) identified $54,967,635 loss per year frominjection-site lesions in the top-sirloin butt. Further-more, in the Final Report of the National Beef QualityAudit−1991 (Smith et al., 1992), concern was raisedthat producers might be changing the anatomical sites(moving the location) at which intramuscular injec-tions are administered.

More recently, George et al. (1995) reported from acontrolled study that injections administered to calvesbefore weaning and thus probably at all stages of thebeef production chain are detectable and pose aquality control problem to the final end-users of beef.

Consequently, three experiments were conducted 1)to ascertain the incidence and severity of injection-sitelesions in the muscles of the beef round and 2) tocharacterize more completely, and to quantify vialaboratory investigation, the pathological changes and



INJECTION-SITE LESIONS: INCIDENCE AND CHARACTERIZATION 3511

Figure 1. Diagram of core sampling technique forWarner-Bratzler shear evaluation of lesioned and controlbottom-round steaks.

potential implications of injection-site lesions on beeftenderness.

Experimental Procedures

Experiment 1. To quantify accurately the nationalincidence and severity of injection-site lesions in themuscles of the beef round, a two-phase study wasconducted from April 1, 1994, to September 1, 1994.This study included five visits to three federallyinspected purveying (steak-cutting) facilities; onevisit was made to a plant in Omaha, NE and two visitseach were made to two plants in Tyler and Dallas, TX.At each of these facilities, bottom-round sub-primalswere fabricated into 170-g Swiss steaks for militaryfood-service uses. To ensure that adequate quantitiesof bottom round cuts were available, pre-arrangedvisitations covered two to three 8-h shifts at eachplant. Audit procedures were similar to thosedescribed by Dexter et al. (1994).

Identification of each bottom round by USDAslaughter-plant establishment number facilitatedevaluation of data by U.S. geographical location. Ineach facility, bottom rounds were fabricated in atempered/frozen state, initially shaped and pressedusing a hydraulic press, and portioned with a meatcleaver; this facilitated examination of each steakfabricated during a plant visit. When an injection-sitelesion was exposed, the affected tissue was excisedand weighed (to the nearest .30 g). Because thesteaks were frozen, difficulties were encountered inthe textural evaluation of the injection-site lesions;this necessitated a modification of the 5-point classifi-cation system, described by Dexter et al. (1994), to a3-point lesion classification regimen. This 3-pointclassification system enabled lesions to be character-ized according to estimated chronological stage of thehealing process (George et al., 1995).

Phase 2 of this experiment consisted of retail auditsperformed from June 1, 1994, to July 31, 1994. Retailaudits were conducted in 10 supermarket stores ineach of the three U.S. metropolitan centers of 1)Seattle, WA; 2) Chicago, IL; and 3) Denver, CO. Eachgeographical location was visited before the com-mencement of the study. During these visits, the datacollection process was explained, using photographsand diagrams, to each retail meat-market manager,and 1-mo supply of survey forms was distributed.Managers updated these forms daily to indicate theUSDA plant of product origin, numbers and types ofround subprimal cuts fabricated, and the weight andclassification of injection-site lesions found during thatday’s production. Each retail audit was conducted for a1-mo period, during which a retail “special” on theround cuts was featured, permitting 80 to 180 roundcuts to be audited in each participating supermarket.

Experiment 2. Concurrent with conducting the firstphase of Exp. 1, a number of normal (n = 40) andlesioned (n = 46) bottom-round steaks were collected

from two of the participating purveying plants forlaboratory evaluation. These steaks were randomlychosen by in-plant Quality Assurance personnel toconstitute a “normal” representation of lesions ob-served in their facility. The steaks were immediatelyvacuum-packaged and placed on Dry Ice for transpor-tation to Colorado State University. After arrival atColorado State University, all steaks were transferredto a freezer and held at −30°C for approximately 30 duntil removal for cooking and shear-force evaluation.

Shear-Force Evaluation. The average age of postmor-tem steak samples collected for shear force evaluationwas 18 d. These steaks were removed from the freezerand allowed to thaw in a 4°C cooler for 24 h beforecooking on an electric Farberware Open-HearthBroiler (Model 350A, Kidde, Bronx, NY) to aninternal temperature of 70°C (“medium” degree ofdoneness). Steaks were cooked to 35°C and thenturned until the desired final internal temperaturewas reached. The steaks were then allowed to cool to21°C before core samples were removed. Beforecooking, the injection sites were marked with ink toensure identification after cooking.

Following cooking, cores 1.27 cm in diameter wereremoved parallel to the muscle fiber orientation fromeach steak. A core was removed from the center of theinjection-site lesion, and four additional cores weretaken at a radial distance of 2.54, 5.08, and 7.62 cmfrom the center of the injection-site lesion (Figure 1).Each core was sheared once with a Warner-Bratzlershear machine. To avoid damage to the Warner-Bratzler shear machine, where necessary, the machinewas stopped at 18.2-kg force, and these readings werereported as 18.2 kg in the data. The average shear-force value at the lesion site and the average of theshear-force values for four cores at each distance of2.54, 5.08, and 7.62 cm from the lesion center werecalculated and recorded for each steak. Controlsamples had cores removed, and shear forces deter-



GEORGE ET AL.3512

Table 1. Injection-site lesion incidence (%) by round cut andretail audit, plant location in Experiment 1

aNeither top-round nor bottom-round cuts were fabricated in Denver.b,cMeans within a row lacking a common superscript letter differ ( P < .01).

Retail audit, plant locationWeightedaverageRound cut Chicago Denvera Seattle

Whole-round 10.11 7.53 13.26 10.03Top-round 2.36c — 26.09b 6.00Eye-round 4.78c 9.09c 23.08b 6.23Bottom-round 5.39 — 8.74 6.67Weighted average 7.00 7.86 12.89 8.45

mined, in the same anatomical locations as thosesteaks that exhibited lesions.

Experiment 3. Normal (n = 12) and lesioned (n =16) paired steaks, two steaks from each lesion, werecollected, transported, and stored as in Exp. 2. In thisexperiment, one steak, randomly chosen, from eachpair of lesioned and normal steaks was cooked, cored,and sheared in the manner described for steaks inExp. 2. The second steak from each pair of lesionedsteaks was then sectioned (longitudinally, in half)such that half of each injection-site lesion remained ineach steak. Corresponding 6.25-cm2 samples werethen removed from each normal and lesioned steak atthe lesion center, 2.54 and 5.08 cm away from thelesion center or corresponding anatomical location inthe control steaks and submitted for 1) soluble andinsoluble collagen assay and 2) histological confirma-tion, examination, and estimation of the relativeconstituent tissue proportions.

Histological Examination. Histopathological exami-nation of the normal and lesioned steak samples wasperformed by the Colorado Veterinary DiagnosticLaboratory, College of Veterinary Medicine and Bio-medical Sciences, Colorado State University. Tissuesamples were placed in 10% formaldehyde solution forfixation and coded for submission such that thepresence/absence of a lesion and(or) the distance ofthe sample from the real or counterpart lesion centerwas unknown to the pathologist evaluating thehistological sections. In total, 30 slides were preparedusing Masson’s trichrome connective tissue stain(Luna, 1968). Tissues were obtained from six normalsteaks and eight steaks that exhibited injection-sitelesions. Microscopic examination, as described byGeorge et al. (1995), confirmed the presence orabsence of injection-site lesions. In addition, a low-magnification microscopic estimate was made, fromeach section, to approximate the proportional percen-tages of muscle, connective tissue, and fat.

Collagen Determination. To assist in explaining thedifferences in Warner-Bratzler shear values observedin Exp. 2 and to quantify accurately the amounts oftotal, soluble, and insoluble collagen, the collagenfractions were separated by the procedure of Hill(1966). Spectrophotometric determination of hydrox-

yproline in the soluble and insoluble fractions wasperformed (Bergmann and Loxley, 1963). Conversionfactors used were soluble (7.52) and insoluble colla-gen (7.25) (Cross et al., 1973).

Statistical Methods. Mean values are presented forpercentage incidence of injection-site lesions, lesiontrim, and lesion location for the rounds that wereaudited. Data representing percentage incidence ofinjection-site lesions were analyzed using the Fre-quency Procedure of SAS (SAS, 1991). Significantdifferences between incidence values as associatedwith the three purveyor locations were determined bycalculating the chi-square statistic. Means represent-ing shear-force values, concentrations of soluble andinsoluble collagen, and proportions of muscle, connec-tive tissue, and fat were computed, and analysis ofvariance with the fixed effect of injection-site lesionpresence was conducted using the GLM procedure ofSAS (1991). Least significant differences were used toidentify statistical differences among blemish weights.Simple correlation coefficients among Warner-Bratzlershear-force values, concentrations of soluble andinsoluble collagen, and proportional percentages ofconnective tissue, muscle, and fat from the injection-site lesion areas in Exp. 3 were generated.

Results and Discussion

Experiment 1. Results of the supermarket retailaudits examining 3,538 round cuts, representing 19packers from eight states, identified a lesion incidenceof 8.45 ± 2.70% with an average lesion trim of 314.7 ±37.72 g. Examination of the lesion incidence by cutand by plant location (Table 1) reveals that (exceptfor Denver, where only whole rounds and bottom-rounds were cut) whole-rounds, top-rounds, eye ofrounds, and bottom-rounds were cut in all three of theregions that were audited. Examination of injection-site incidence by plant location, reveals that Seattlehad a greater ( P < .01) lesion incidence, for the top-round and eye of round, than did either Chicago orDenver. The presence of injection-site lesions in thetop-round and eye of round suggests that this may bea convenient and favored anatomical location for




Table 2. Injection-site lesion classification and lesion trim (± SE) in bottom-roundcuts examined in purveying facilities in Experiment 2

aWoody callus and clear scar lesion classifications represent chronologically aged injection-site lesions.bCystic lesions represent injection-site lesions containing fluid, indicative of recent pharmaceutical

injection.

LesionLesion classification, Lesionclassification % trim, g

Woody callusa 50.39 215.2 ± 20.87Clear scara 49.42 168.1 ± 20.87Cysticb .19 207.8 ± 39.01

Total: 100.00 Avg: 191.6 ± 55.20

giving injections to calves; this would be a moredifficult anatomical site to access when administeringinjections to older cattle. Classification of theseinjection-site lesions revealed that 93.2% were chrono-logically older (“woody callus” and “clear scar”),whereas 6.69% were recently administered (“cystic”).Average lesion trim was 345.9 g for “woody callus,”288.9 g for “clear scar,” and 238.4 g for “cystic” lesions.

Results of audits conducted in purveying facilities,examining 15,464 bottom-rounds, representing sevenpackers in four states, revealed a lesion incidence of10.04 ± 6.51% with an average lesion trim of 191.59 ±55.2 g. As a percentage of total lesions, lesionclassification and weights are presented in Table 2.Overall, the classification of 93.20 and 99.91% oflesions detected in the retail and purveyor audits,respectively, as “clear scars” or “woody calluses,”chronologically aged lesions, supports recent reportsby Dexter et al. (1994) from national top-sirloin buttaudits that 90% of the injection-site lesions cancurrently be classified as “older,” originating early inthe cow-calf, stocker, or early feeding periods.

Examination of the incidence data for injection-sitelesions collected during the purveyor audits by ge-ographical plant of origin revealed an incidence rangeof 3.35 to 20.84% among the groups of bottom-roundcuts that were audited. Closer examination of thelatter data (based on cattle breeds commonly har-vested at certain facilities) suggested that the highinjection-site lesion incidence was a particularproblem from long-fed Holsteins (“calf-fed” Holsteins),which are frequently given injections as calves in thisanatomical region, because, at this stage of physiologi-cal development, the round is a large muscle masscapable of accommodating intramuscular injections.

In total, 19,002 round cuts were examined, for alesion incidence of 9.74 ± 5.14%, and an average lesionweight of 211.8 ± 79.88 g, which is similar in incidenceto the data reported for the top-sirloin butt (Dexter etal., 1994). However, the lesion weight (211.8 g) isconsiderably greater than the most recent averagelesion weight of 123.39 g reported by Dexter et al.(1994) for lesions removed from the top-sirloin butt.The large size of lesions reported in the present studymay be attributable to a large volume of an irritant

being injected and(or) injection at early ages, suchthat the lesions enlarged with age, as has beenreported in the controlled studies of George et al.(1995).

Dexter et al. (1994) reported a decline in injection-site lesion incidence from 21.27% in July 1991 to10.87% in March 1993. Moreover, a recent 1994National Animal Health and Monitoring System(NAHMS) cow-calf productivity survey (VS/APHIS/USDA, 1994) identified the producer-favored anatomi-cal sites for intramuscular injections as 1) upper hip52.0%, 2) lower hip 9.6%, 3) rump along tail 14.7%,4) shoulder 3.4%, and 5) neck 19.8%. The latter auditfurther identified the preferred sites for veterinarian-delivered intramuscular injections as 1) upper hip47.7%, 2) lower hip 8.7%, 3) rump along tail 8.9%, 4)shoulder 6.5%, and 5) neck 27.0%.

Although no data exist reporting the incidence ofinjection-site lesions in the muscles of the round for1991, a portion of the 10.4% reduction in lesionincidence in the top-sirloin butt may be accounted forby hypothesizing that those shots not given in the top-sirloin butt were administered into the muscles of theround (note the injection-site lesion incidence of 9.74%reported in the present study).

Experiment 2. Warner-Bratzler shear values forcores from the site of the injection-site lesion and fromsites located 2.54, 5.08, and 7.62 cm away from thelesion center were 13.87, 10.00, 7.60, and 5.80 kg,respectively, for lesioned steaks, which was different( P < .001) from corresponding measurements of 3.97,4.11, 4.30, and 3.90 kg, respectively, for control(normal) steaks (Figure 2). Eilers et al. (1993)reported that a shear-force value of 3.86 kg or less wasindicative of “restaurant quality” tenderness in asteak, whereas a shear-force value of 4.45 kg was theupper limit of tenderness for sale of a steak to theretail trade. From that same study (Eilers, 1994) theaverage force required to shear U.S. Choice top-roundsteaks was 4.27 kg.

In wound healing, architectural changes in thecollagen matrix occur as a result of the intricateprocess of remodeling. Concomitant with this deposi-tion and maturation of collagen is a rise in tensilestrength (Harkness, 1968). Quantitative changes in



GEORGE ET AL.3514

Figure 2. Warner-Bratzler shear-force for lesioned andcontrol bottom-round steaks. a,bMeans within a distancefrom the lesion core lacking a common letter differ (P <.001).

acid mucopolysaccharides accompany the collagen andtensile strength changes (Dunphy and Udupa, 1955).Bryant and Weeks (1967) reported the best deter-minant of the gain in tensile strength to be the ratio ofwound collagen to mucopolysaccharide, and thatalterations in the cohesive forces between collagenmicrostructures were directly related to this ratio.Milch (1965) reported that it was the number ofeffective network chains, per unit volume, and not thetotal number of chains, that has the greater influenceon load-bearing structure. Results of the present studyprovide concrete evidence that when injections areadministered intramuscularly into beef cattle, thetenderness of affected tissues is significantly reducedat, and in an area up to, 7.62 cm away from the lesioncenter.

Experiment 3. Results of Warner-Bratzler shear-force determinations on cores from lesioned steaks vscontrol (normal) steaks were 17.03, 11.93, and 9.44kg vs 4.98, 5.31, and 5.88 kg, respectively, for1.27-cm cores taken at the site of the lesion and atdistances 2.54 and 5.08 cm away from the lesioncenter, respectively. These results support the findingsreported in Exp. 2.

Total collagen concentrations of tissue samplestaken from the site of the lesion and at sites 2.54 and5.08 cm away from the lesion center were 36.12, 19.85,and 8.16 mg/g, respectively, for the lesioned steaks vs10.67 mg/g of collagen in muscle samples from thecontrol steaks. Concentrations of soluble collagen(heat labile) were 2.56, 1.27, .58, and 1.01 mg/g forsamples taken at the site of the injection-site lesion,for samples 2.54 cm away, for samples 5.08 cm away,and for control steaks, respectively (Figure 3).Moreover, concentrations of insoluble collagen fromthe site of the lesion and from sites 2.54 and 5.08 cm

away from the lesion center were 33.56, 18.58, and6.16 mg/g, whereas that for control steaks was 10.67mg/g.

The significant increases in total, soluble, andinsoluble collagen concentrations at the lesion center,which decrease in concentration as the radius from thelesion center increases, provides evidence that afibroproliferative process has occurred subsequent tointramuscular injection of a pharmacologic agent. Inthis experiment, it is interesting to note that coresamples taken at a distance 5.08 cm from the center ofthe lesion required greater ( P < .05) shear-force tosever than cores from corresponding control steaks,but that the amount of insoluble (heat stable)collagen was not significantly different, and wasactually numerically lower, than in control steaksamples. A possible explanation for the latter findingis that the collagen assay we employed directlymeasures hydroxyproline residues and that the per-centage of hydroxyproline residues differs for collagensof type I (11.3 %) vs type III (15.0 %), as wassuggested by Etherington and Simms (1981). Thesignificant correlations (r = .67 and .50; P < .001)between Warner-Bratzler shear values and insoluble,as well as soluble, collagen concentrations indicatethat the increase in these parameters accounts for themajority of the differences in shear-force values.

Light et al. (1985) observed a correlation betweentoughness and collagen content of muscles. Shermanet al. (1980) reported that in connective-tissuereactions to injury in wound healing, or in afibroproliferative process, there is initially neosynthe-sis of collagens of pericellular type V and basementmembrane type IV, and eventually, synthesis anddeposition occurs of fine, fibrillar type III collagen,which is followed closely by the formation of a matrixcomposed of interstitial type I collagen resemblingscar tissue. Moreover, this type I collagen is reportedto have a larger fiber diameter than type III collagenthat is correlated with decreased muscle tenderness(Gay, 1983). Concomitant with this increase inconcentration of collagen and the increase in diameterof collagen fibrils is the loss of solubility of collagen;collagen solubility decreases progressively with agedue to the development of heat-stable covalent inter-chain bonds (Bailey, 1972).

Histological examination of all these samples con-firmed the diagnosis of injection-site lesions, as wasdescribed by George et al. (1995). From visualestimations, the relative percentages of connectivetissue, muscle, and fat (Figure 4) were 1) 45.63,30.00, and 19.38%, respectively, at the site of thelesion center; 2) 21.25, 52.50, and 28.75%, respec-tively, at sites 2.54 cm from the lesion center; 3) 8.13,75.63, and 15.63%, respectively, at sites 5.08 cm fromthe lesion center; and 4) 7.50, 80.83, and 11.67%,respectively, in control steaks. This supports thefindings from the collagen assays revealing that




Figure 3. Soluble and insoluble collagen concentrations for lesioned and normal bottom-round steaks. a,bMeanswithin a measurement parameter lacking a common letter differ (P < .001).

Figure 4. Quantitative proportions of connective tissue, muscle and fat as measured histologically from lesionedand control bottom-round steaks. a,b,cMeans within a tissue type lacking a common letter differ (P < .001).

severe disruption of the relative tissue proportions hasoccurred in, and adjacent to, these lesions. Moreover,the numerical proportional differences in connectivetissue and muscle between samples taken at sites 5.08cm from the lesion center vs those from control steaksamples may (in part) account for the disparity

between the significantly different Warner-Bratzlershear values and the nonsignificant differences in thecollagen assays at these two tissue locations. Correla-tion coefficients between Warner-Bratzler shear meas-urements and the relative tissue proportions ofconnective tissue, muscle, and fat were .68, -.80, and



GEORGE ET AL.3516

Figure 5. (a) Histological section of the center of an injection-site lesion from a bottom-round steak, stained withMasson’s stain. The tissue consists of sheets of fibroblasts with extensive collagen deposition. (b) Histological sectionof tissue 2.54 cm from the center of an injection-site lesion in a bottom-round steak. There is a combination of densefibrous connective tissue (upper right) and mature adipose tissue (lower left). (c) Histological section of tissue 5.08 cmfrom the center of an injection-site lesion in a bottom-round steak. This section includes a mixture of partiallydegenerated muscle fibers, mature connective tissue, and occasional adipose cells (clear spaces). (d) Histopathologicalsection from a control (normal) bottom-round steak. This section includes normal muscle fibers separated by clearareas that are a result of sectioning artifact. Line = 1.0 mm in each illustration.

-.34, respectively. Figures 5a,b,c, and d are micro-graphs of sections taken from steaks affected byinjection-site lesions, at the center of the lesion and atsites 2.54 and 5.08 cm away from the lesion center, aswell as for a normal bottom-round steak, respectively.The lesion center (Figure 5a) contains dense sheets offibroblasts with extensive collagen deposition, which isgradually replaced by adipose tissue as the distancefrom the lesion center increases (Figure 5b). At agreater distance from the lesion center (Figure 5c),there is a further reduction in the concentration ofconnective and adipose tissue, replaced by degeneratemuscle fibers; this may be contrasted with normalbottom-round muscle tissue (Figure 5d). George et al.(1995) reported similar histological findings (dense,mature connective tissue with a few trapped musclefibers and sheets of adipose tissue), resulting from the

intramuscular injection of commercially availablebiological and pharmacological preparations into bran-ding- and weaning-age calves.

A distinction exists between individual fiber necro-sis, such as that following micropuncture lesions andmild inflammatory myopathies, in which the base-ment lamina of the muscle fiber (and the en-domysium) remain intact and serve as scaffolding forregeneration of the necrotic segment, and the non-selective type of change that occurs after trauma,hemorrhage, ischemia, and acute local drug toxicosis.In the latter circumstances, interstitial tissues arealso damaged and the continuity of the basementlamina and endomysium of the individual musclefibers may be lost (Kaparti et al., 1974; Paakkari andMumenthaler, 1974; Kakulas, 1975; Kakulas,1982a,b). After muscle damage, the most effective




regeneration is reported to occur where the basementlamina and endomysium remain intact; the newlyformed fibers will then be formed within the originalsarcolemma tubes and will, therefore, have an orderlyorientation parallel with the remaining fibers in themuscle (Kakulas, 1975). However, if the scaffoldformed by the basal lamina is disrupted and(or) if thebasic pathologic process does not subside, regenerationwill be less orderly, and less effective, and newlyformed fibers will be surrounded by proliferatingfibroblasts (Adams et al., 1962). Kakulas (1982b)reported that intramuscular injection of either chlo-ramphenicol or oxytetracycline produces damage toskeletal muscle with fibrosis in mice, and thatstreptomycin, cephalothin, and amino benzyl penicil-lin cause similar but less severe changes. Electronmicroscopy has revealed degradation of muscle fibers,motor end plates and peripheral nerves 1 d after asingle injection of chloramphenicol (Yamamura,1977). The integrity of the basement lamina is alsothought to be important for the re-innervation andfunction of new muscle fibers (Burden et al., 1979).

George (1994) reported from field study data thatthere can be ossified tissue that results from in-tramuscular administration of pharmaceuticals incattle. Reddi et al. (1977) reported that followingsevere granulation reactions, mesenchymal cells maydifferentiate into chondroblasts that produce type IIcollagen that are then replaced by bone osteoid thatcontains type I collagen, simulating endochondralbone formation occurring during skeletal development.

Implications

Injection-site lesions are a serious quality controlconcern, requiring labor to remove from steaks andresulting in substantial tissue and monetary loss tothe U.S. beef industry. Utilizing a modification of thelogic used to derive industry losses from nationalaudits of injection-site damage in the top-sirloin butt,injection-site lesion damage in the muscles of theround currently represents a loss of $28,160,288 peryear to the U.S. beef industry. However, concern mustbe raised as to whether the current trimming proce-dures that are employed adequately resect the volumeof tissue required to ensure no adverse consequenceson beef tenderness and palatability, and whether ornot the true costs, because of customer dissatisfaction,from intramuscular pharmaceutical administrationare accounted for in such analyses. The real costscould be far greater than those resulting from tissuelosses alone.

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