Dreyer, JH

Gouws, PJ

Naudé, RT

English

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S.Aft ,J.  Anim ScL 2,  109- l  I2 (1972)THE INFLUENCE OF SI.AUGIITER TECHNIQUE AND HISTOI'GICAL TREATMENToN MUSCLE FIBRE DIAII{ETER OF l.ow AND HIGH pH1 PORK MUSCLEJ.H. Dreyer, R.T. Naudd and P.J. GouwsAnirrul and Daty Science Research Institute, IreneO$OMMING: DIE INVT,OED VAN SLAGMETODE EN HISTOLOGIESE BEHANDELING OP SPTERVESELDETJRSNEE VAN LAE ENHOts pH, VARKSPIER'n Procf was uitgevoer om die invloed van twee slagmetodes en drie metodes van spierfiksering op die mikrostnrttuur van die vark-spier te bepaal Die spier van varke wat met die penpistool bedwelm is het 'n baie laer gemiddelde pH1 (5J0 gehad as dievarkewarniebedwelm was nie (6,70). Statisties betekenivolle verskille in spierveselteursnee is gwind, wat aan die slagmetode toegeskryf kon word."Reuse vesels" soos detrr Cassens, Cooper & Briskey (1969) beskryf ig is gevind in spiermonsters van varke wat vo[ens albei metodes geslag isSUMhURYAn crpcrirnent was conducted to assess the effect of two slaughter methods and three methods of nrusck l-rxation on the microstructureof pig muscle. The muscle from the pigs stunned with a captive bolt had a much lower average pH, (5,50) than the unslunned pgs (6,?0).Stalistically significant differences in fibre diameler due to method of slaughter ard method of fixation were recorded. 'Giant fibres" as de-scribcd by Cassens, Cooper & Briskey ( 1969) were found in muscle samples taken from pigs slaughtered by both methodsThe pale, soft and exudative (P.S.E.) phenomenonin pigs is caused by a rapid fall in muscle pH (pHl .6,0at 45 min.) Wst mortem wlile muscle temperature is stillat a reasonably high level (, 35oC) (Briskey, 1964). InSouth Africa it has been established that stunning pgsby captive bolt gives rise to low muscle pH t valuespost mortem. A recent country wide survey of methods ofslaughter indicate that percentages of pH I values lowerthan 6,0 as high as 72% can be expected when thecaptive bolt method is used (Klingbiel & Naud6, l97l).To investigate certain traits of low pHl and normalmusculature a low pH t was induced in the M. longissimusdorsi of a group of pigs stunned by captive bolt pistol andcompared with normal muscle obtained from pigs ex-sanguinated without stunning. illuscle fibre size of these twogroups was studied following different processing prccedures. "Giant fibres" were observed in both low pH 1 andnormal musculature. According to the literature (Cassenset al, 1969) 'Gianl fibres" are only associated with P.S.E.or low pH1 muscles.ProcedureEight Landrace x Large White crossbred pigs fed ahigh level of protein ration ( l6il protein) were dividedinto two groups with a mean carcass weight of 65 kg foreach group. One group was stunned by captive bolt pistolto induce low pH 1 nrusculature while the other group wasexsanguinated without stunning. The pH and temperatureof the M. longissimus dorsi at the level of the llth. l2thand lSth thoracic vertebrae were determined 45 min.post mortem- Twenty-four hours post mortem a sectionof the same muscle was taken at the saxne position. Allspecimens for processirg were taken in the same area of themuscle and were cut tranwersely to the longitudinalaxis of the muscle fibres and fixed in l0"l neutralFormalin, Carnoy's and Zenker's according to the pre-scribed formulae ( Luna, 1968). All fixed specimens wereprocessed and embedded in paraffin wax with 5 % ceresine(M.P. 57o-60oc). Sections were cut at 7 pm and stainedwith Delafield's haematoxylin and counterstained in eosin.Specimens used for cryostat sectioning were im-merscd in liquid nitrogen prior to deep frceze storagingat -20oC. These were sectioned at l0 um and stainedwith Mallory's Triple Stain.Homogenized specimens were prepared accordingto the method of Hegarty & Naudd (1970) for immediatemeasurement of the diameter of 100 muscle fibres.One hundred muscle fibres from samples prepared bythe former four methods were measured per slide on aReichert Visopan at a magnification of 500x. Transversesections were measured across their widest long axisand the widest short axis perpendicular to the widest longaxis (Plate la).An analysis of variance on the results was carried outaccording to the method of Guenther ( 1964).Results and DiscussionEffects of sloughtering methodln Table I the differences between low and highpH t musculature is clearly illustrated showing that thepH1 of the exsarguinated pfs is 6,7 while that of the pigsr@g ffi,: '4.1)t . t u t  4t } f*.:$Plute l. -a. The axes along which cross-sectiorul measurements were token (X 840).b. Tmnsudation of the cell cgntent into extracelluhr sryces as indicated by arrows (X 260)c. A number of "Giont fibres" as indicvted by arows (X 12).l l 0Ttbh IMutcle fibre diometu of lou, pH I and nontul ptg M.longissimus dorsi (um)ptl I Carcrr No. Cemoy'sMasckgrcrFormrlinZcnlcr'r Cryoctet Homogortizctrci.nt Fibte"Mcan5.70 54,9t{.I72 339,01 41.56411.23s64,39617.29 65,E7(n = 89)Exsrng-uinetodCeptive BoltMcrn5.50 64.4738,08g 935.05 39.95l040,08l l54.93l 241 .62  ? lB t(n = 53)l 341 .17l {  t537,03 40,?6l6.13,66l759.66P  <  0 , 0 1  6 : 1 2 ;  l 7 :  1 3 . 1 4 . 1 5 . 1 6 ;  5 : 1 , 2 . 3 . 4 ;  l l : ? , 8 , 9 , 1 0 ;  5 : l l ; 4 :  l 0P <  0 , 0 5  l : ? ;  1 4 : 1 5stwmcd by captive bolt is 5,5. The anelyrir of varianccemphasizcd that the method of slaqhtering had a rtatidic-aly significant (P < 0,01) effect on libre cizo. Thir opdition resulting from a lory ptll in r murch ir slro rpflect-cd in the ap'pearance of the meat when cut md cxposed(Naudi, 1972i. Measurernents on mulcle fibrc diamctcr(Tabh l) rtrowcd r statistical signilicant diffcrencp for thcmcens ( 6:12) at the P < 0,01 lsvtl for thc two rlaughtergroups indicating a drrinloge in fibrc sizc of the lowpHt musclcs.The decrpasc in libre diamcter can be attributcd toa pooror watcrholdiry capacity of the myofibrillar protcinrof the musclc fibrer expoed to a rapid pst mortemglycolysis(Carroll l97l) rerultirg in thc trrnnrdation ofintracc[ul8r moisturc into the intraccllular spoocs (Plrte I bl.Evidently this is the reason for the moist appcerurce oflow pH1 or P.S.E. pork on the exposed surface of musclcs.Effects of t aboratory pocessingIt is apparent thet both thc homogcnizer (5:ll)(Table l) and the cryostet (a : l0)treatmentsarernritiwenough to show differcnces botwecn the two rlaryhtcrmethods at the P < O,0l lwel Mcarurcmcots on fibrediameter of spccirnens from both rlaughtcr mcthods fxedin Carnoy's (l:7) $ow thir rcnsitivity only at thc 5f,lcvel of rigruficance while the measurtmcntt on ryccimenrfixcd in lOl neutral Formalin (2:8) and Zcnkor's (3 :9)show no statistical diffcrencc st all between tho two slaqhter methodl. Shrinkage as such could also be dus to thecffecls of hbontory procadrg. Howcvcr, since all specinrcru wsre trcrted in the rame manncr thc stetbticaldiffcrencor in fibre diametcr betwecn thp two groups canbc attributed to th? deqhter method and not to shrinktte durfutg proccdng. No interection could be strownbetwecn slaughter rnGtlpd ard bbontory proccdng.Thir decrme in murcle fibrc diacraer is all themore notioeable whcn comparirry diaaneten of fibres fixedin Carnoy's, l(}l Formalin ard Zcnke/r on thc onc hand,with thc unfxcd fibres of cryoctat sstiora and those ofthc homogenizcr on thc other hand (Table l). Formalinmaterid drowed thc grcatest srnount of rtrrinkage of thethrco fixatives urd during laboretory proccrsing whichcoincides with findirys of otherworkers(GoHspin\ 196l)."Giant ftbres"During thccc invcstigations thc prerncc of "giantfibrer" as described by Casscns et al, (1969) were noted(Phts lc). Thae fibrec werc klentiflcd morphologicallybut contnry to the findirgt of thc above workers theywere abo obscrved in pctions of murcleg from animals notconformiry to the charactoristicc of lmr pHl pork muscle.Thcec morphologicelly difforent fibres occurred in bothgroups urder study in comparable numbcrs (Table l).Sincc they cen only be identifred in tranryersc section atthis stagc, mGasur?m€nts could only be made in thst plane.In the cxrarryuineted group thc mcan diameter ofthesc fibrer was 65,87 um (n = E9) urd in the captive bohtrcup, 71,93 Um (n =63) for the thrce proccssing proced-l l lures as well as cryostat sectioffi. Owing to low numbersand because thcy do not appesr in every scction a statistic,-al analysis w:rs not attempted. The reason for the largerfibre diameter of thes fibres in the low pH1 Broup couHnot tre explained but the resisteocs of theso fibres to theinfluence of rapid Wst monem glycolysis and also to theinfluence of laboratory proccssirg can be infenpd fromthese measuremcnts and the fact that they retain theircircular or slightly orral dupe.ConclusionsA low pt{t h musclc can be induced by the darryhter-ing method. This low pH1 ir usually associated with P.S.E.musculature in pig* Histologftally this condition is ex-hibited by the statisticelly highly significant decrease infibre size of the low pHt muscles comperod to theother group. This decrease in fibre sizc can be rscribedto the grpater degree of transudation of ccllular fluid tothe extracellular spacas of tha mu*ls with a low pH 1as compared to the musclc with a high pH1. Of thcfixatives uscd, l0% Formalin rhowcd thc greatest shrinking influencc on the muscle fibres of the mucles fromboth group's, folbwed by Zcnkcr's and Carnoy's tcspcctive-ly. The homogenizer and cryostat method are sensitive todifferenccs in murcle fibre diameter induccd by the slat4ht-ering method in a highly significant way (P < 0,01r.'Giant fibrcs" are found to occur in both low pH,and normal rnusculature. lt can be inferred from thisstdy that "giant fibrcl" are not viribly affected by thedarryhtering method or laboratory procerdng. Furtherinvestfation into the bioclemical characteristiqs of thecefibrcs is needed to clarify thcir specific rcsistance to changesas manifested by their relatively large size and round oroval slrapes ln addition, thcy have a characteristic stainingreaction in contrast to thc irregular polygonal shapesand differcnt staining reaction of the bulk of the musclelibres.ReferenccrBRISKEY. E.J., 1964. Adv. Fd Res 14,9O.CARROLL, M.A., 1971. S. Afr. J. Anirn Sci. l. 169.cAssENs, R.G., cooPER, C.C. & BRISKEY. 8.J., 1969.Acta ncuropath., Berl. 12,3OO.GOLDSPINK, G.. 1961. Nature, Lond.192 (4809), 1305.GUENTHER, W.C., 1964. Anal-vsis of nariancc. New York:Prentice Hal[HEGARTY, P.V.J. & NAtDi, R.T., 1970. Lrb. Practice1 9 ,  l 6 l .KLINGBIEL, J.F.G. & NAUDE, RJ., 1971. S. Afr. Tydskr.Vcelc l, 109.LUNA, L.G., 1968. Menual of histological staintury mcthodsof the A.F.|.P. [,ondon: McGnw Hill.NAUDE, R.T., 1972. Jl. S. Afr. vet. Ass. 43 (l), 47.l t 2

The influence of slaughter technique and histological treatment on muscle fibre diameter of low and high pH1 pork muscle

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The influence of slaughter technique and histological treatment on muscle fibre diameter of low and high pH1 pork muscle

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