Composition and cross-sectional area of muscle fibre types in relation to daily gain and lean and fat content of carcass in Landrace and Yorkshire pigs Marita Ruusunen Department of Food Technology, P.0.80x 27, FIN-00014 University ofHelsinki, Finland, e-mail: marita. ruusunen @ helsinki.fi Marja-Liisa Sevon-Aimonen Agricultural Research Centre of Finland. Institute ofAnimal Production, FIN-31600 Jokioinen, Finland Eero Puolanne Department of Food Technology, P.0.80x 27, FIN-00014 University ofHelsinki, Finland The muscle fibre-type properties of longissimus were compared between Landrace and Yorkshire breeds and between the sexes in an attempt to shed light on the relationship of these histochemical parameters to animal growth and carcass composition. Muscle fibres were classified into three groups, type I, type lIA and type 118, using the myosin ATPase method. At a given live weight, the cross- sectional area of type I fibres (CSA,) was smaller (p<0.01) and the cross-sectional area of type 118 fibres (CSA 11B ) larger (p<0.01) in longissimus of Landrace than in that of Yorkshire. The CSA 118 (pcO.Ol) was larger in gilts than in castrated males. At an average live weight of 97 kg, the Landrace pigs were significantly younger (p<0.01) than the Yorkshire pigs. The pH! value of Landrace was lower (p<0.01) than that ofYorkshire. The percentage of high-value cuts in carcass with head (M%) was lower (pcO.Ol) and the percentage of fat in back and loin (F%) higher (p<0.01) in castrated males than in gilts. The cross-sectional area of loin (CSA|o,n ) was larger (pcO.Ol) in gilts than in castrated males. All the histochemical and other traits varied considerably between the animals. The correlations between histochemical properties and growth and histochemical properties and carcass composition were rather low. Key words: pig breed, muscle fibre cross-sectional area, longissimus, carcass traits ntroduction The pig breeds or crosses used for pork produc- tion tend to vary from country to country. The breeding goals also vary, and hence there may be genetic differences in the same breed between countries. The traditional pig breeds reared in Finland are Landrace and Yorkshire. Both have been bred intensively and separately for many years, although with similarbreeding goals. The most important selection criteria in pig breed- © Agricultural and Food Science in Finland Manuscript received September 1996 593 Voi 5 (J996): 593-600. AGRICULTURAL AND FOOD SCIENCE IN FINLAND https://www.c-info.fi/en/info/?token=6p1CC6S7zWswZ7Kc.EHjxSqEGleBCQrfX7wKvpA.xBwA5JkJEBDnbfFiPJ-hx2CpAWZc-wyxQ6MMPZ-MKsL2CsJEd_3GGimmWEsnyZw7ngXaYZ3bHe4HB4zDpawGyC0OKBbIu7zJzjLgVLwVG8aeO1ThkR_dJSMjH7BoJrFd0JYPsVejQpdeGIjM9EyPGpg-NMWpuBvzyDTuRGwqLJM9jsxjsqYP6u6sDRuSiiRRikJwk9bRgSc0dYQiiLgBY3mbDxbR8DTLV0F3rMdFMvnKoO_vjt7d4Gnk8uIkBEng6U-Mbepx72PYJcOE_c2214_CZr5V7rca8kq-77t0JdAOTOLuzYLEcGJP-sbb8_2- Ruusunen, M. et al. Composition and cross-sectional area of musclefibre types ing have been high daily gain and carcass lean- ness. Genetic selection is thought to influence muscle fibre composition by increasing the number and area of type II fibres in domestic pigs (Staun 1972, Swatland 1977, Rede et al. 1986). The muscles of wild pigs have a higher percentage of type I and type lIA fibres and a lower percentage of type 118 fibres than do do- mestic pigs, and also the CSA of muscle fibres is smaller in wild pigs than in domestic pigs at the same live weight (Bader 1983). Muscle fibre composition affects both growth and lean meat content. Miller et al. (1975) found in longissimus and Dwyer et al. (1993) in semi- tendinosus that faster growing pigs appeared to possess more, but smaller, fibres than slower growing pigs at the same live weight. Staun (1972) and Miller et al. (1975) established that the total number of muscle fibres in longissimus was more closely related to muscle mass than was fibre diameter. Dwyer et al. (1993) reported similar results in their study on porcine semi- tendinosus. A positive correlation has also been found between the percentage of type 118 fibres in longissimus and the CSA of pork loin (Bader 1981,Fiedler and Otto 1982,Wegner and Ender 1990,Fewson et al. 1993). Tornberg et al. (1993) pointed out that in lean carcasses, the CSA of muscle fibres is larger than that in fat carcasses of the same weight. This study sought to compare the histochem- ical properties ofFinnish Landrace andYorkshire breeds, to establish the differences in these prop- erties between the sexes and also between pigs within the same breeds, and to investigate the relationships between these histochemical prop- erties and animal growth and carcass composi- tion. Material and methods The material consisted of 107 pure-bred pigs, 54 Finnish Landrace and 53 Yorkshire (N=s3), raised at four different test stations. The proge- ny of 39 Landrace and 41 Yorkshire sires were used. The pigs were slaughtered at an average live weight of 97 kg. Before slaughter, the pigs were allowed to rest overnight. They were then stunned with carbon dioxide. The day after slaughter, the left side of the carcass was dis- sected. Histochemical properties Muscle samples for histochemical analysis were taken from the right side of the carcass about 30-40 min after exsanguination from longis- simus between the 13th and 14thribs. The mus- cle sample, about 20 g, was cut into pieces meas- uring 0.5x0.5x1.0 cm, which were frozen in liq- uid nitrogen and stored at -80 °C until analysed. The fibres were classified into three groups, type I, type lIA and type 118, with the myosin ATPase method (Brooke and Kaiser 1970) and an acid preincubation solution(pH 4.6). Stained sections were examined with an image analysis system using CUE 2 Planomorphometry soft- ware (Olympus, Germany). The magnification was 160x. The fibres were counted in an area of about 0.9 mm2 , containing about 150-200 fibres. Three different pieces of each muscle sample were stained, and thus 450-600 fibres were ana- lysed. The following parameters were comput- ed: percentage of type I (I% number ), type lIA (lIA% ) and type 118 (118% ) muscle fi-number 7 J r v number 7 bres, percentage of the total area of type I (I%area ), type lIA (lIA% ami ) and type 118 (118% area ) mus- cle fibres, and the cross- sectional area of each fibre type (|4m2 ) (CSA,, CSAi|a and CSA I|B ). The number of muscle fibres in longissimus per whole loin area (Numfjbre ) was calculated as the loin area (at last rib) (CSA |ojn ) divided by the average fibre cross-sectional area (CSA fibre ). Other traits The following station test traits were used in the study: age at slaughter (age), live weight at the end of the test (LW), average daily gain during 594 AGRICULTURAL AND FOOD SCIENCE IN FINLAND the test period adjusted to a weight of 25-100 kg (ADG), carcass weight (CW), loin area at 13- 14 rib (CSA |oin), percentage of fat in back and loin (F%) and percentage of high-value cuts in carcass with head (M%). The pH value of longissimus was measured between the 13th and 14th ribs at 45 min and 24 h (pH 2 ) post mortem on each carcass (Knick Portamess pH meter 752 equipped with a Xerolyte electrode; Ingold Xerolyt L0T406- M6, Germany). Statistical methods Data were analysed with the GLM procedure and the CORR procedure of the SAS/STAT program (SAS Institute 1990). The effects of breed and sex were studied using the following statistical model: y... = u + breed + sex + e...J ijk i j ijk y.Jk = observation u = overall mean breed, = effect of breed (i=l,2) sex, = effect of sex (j= 1,2) e... = residual termijk The relationship between histochemical prop- erties and animal growth and between histo- chemical properties and carcass composition was described with correlation coefficients. The ef- fect of breed and sex was taken into account. Results and discussion Difference in histochemical properties between breeds and sexes The muscle fibre composition of different breed has been compared in only a few studies. Here, longissimus ofLandrace contained a significant- ly higher percentage of type I fibres and a lower percentage of type 118 fibres (pcO.Ol) than did that of Yorkshire (Table 1). The percentages of muscle fibre types ofanimals within both breeds varied, however, more than did those between the breeds on average. On the basis ofhistochem- ical properties, similar pigs can be found in both breeds. Miller and coworkers (1975) did not find any differences in fibre type composition in long- issimus between Hampshire, Yorkshire and Hampshire x Yorkshire pigs, and Essen-Gustavs- son and Fjelkner-Modig (1985) found none be- tween Swedish Landrace, Yorkshire and Hamp- shire pigs. Here, no significant difference (p>0.05) was found in fibre type composition between the sexes (Table 1). At the same live weight, however, the CSA, was smaller (p<0.01) in longissimus ofLandrace than in thatofYorkshire, but the CSA,m was larg- er (p<0.01) (Table 1). In Danish Landrace-York- shire crossbred pigs the CSAs of type I and type 118 fibres were 2824 and 6120 pm 2 , respective- ly at a live weight of 90 kg (Oksbjerg et al. 1990), and in Swedish Landrace-Swedish Yorkshire crossbred pigs 3200 and 5600 pm 2 , respectively at a live weight of 100 kg (Essen-Gustavsson et al. 1992). The CSAs of different fibre types re- ported in various studies are difficult to com- pare because the muscle samples were excised from the carcasses at different times post mor- tem, and the CSA measurements were made on sections stained with different methods. In this study, no significant difference was found in the estimated Numr . between Landracefibre and Yorkshire or between sexes. The CSA |IB (5051 pm 2 ) (p<0.01) and the CSA fibre (4476 pm 2 ) (p<0.05) were larger in gilts than in castrated males (4593 and 4153 pm2 , respectively). Karls- son et al. (1994) also showed that the CSA of all fibre types was significantly smaller in longis- simus of intact Yorkshire male pigs than in gilts at a live weight of 103 kg. Difference in growth and carcass traits between breeds and sexes When pigs grow, the CSA of all fibre types grows as well, but the area of type lIA and type 118 is 595 Vol. 5 (1996): 593-600. AGRICULTURAL AND FOOD SCIENCE IN FINLAND Ruusunen, M. et al. Composition and cross-sectional area ofmusclefibre types Table 1.The means and standard deviations ofstudied traits (mean ± s.d.) of Landrace and Yorkshire breeds and ofcastrated males and gilts. Breed Sex Statistical significance Landrace Yorkshire Castrates Gilts Breed Sex Number of animals 54 53 49 58 Histochemical traits 1% _ 13.2 ±3.7 9.9 ±3.8 11.2 ±3.1 11.8 ±4.8 ** NS number lIA% . 9.0 ±3.8 8.6 ±3.1 8.7 ± 3.3 8.9 ± 3.7 NS NS number 118% _ 77.9 ± 3.9 81.6 ± 3.8 80.1 ±4,0 79.3±4.5 ** NS number 6.9 ±2.1 6.4 ±2.4 6.6 ±2,0 6.7 ± 2.5 NS NS lIA% 4.9 ±2.3 5.3 ±2.0 5.0 ±2.2 5,2 ± 2.2 NS NS area 118% 88.2 ±2.4 88.3 ±2.6 88.4 ±2.8 88.1 ±2.2 NS NSarea CSA,, 1000 pm 2 2.4 ±0.5 2.7 ±0.6 2.4 ±0.5 2.6 ±0.6 ** NS CSA ]1V 1000pm 2 2.4 ±0.6 2.6 ±0.5 2.4 ±0,5 2.5 ±0.5 NS NS CSA ]]B , 1000 pm 2 5.1 ±0.9 4.6 ±O.B 4.6 ±0.7 5.1 ± 1,0 ** ** CSA fibre, 1000 pm2 4.5 ±O.B 4.2 ±0.6 4.2 ±0.6 4.5 ±O.B ** * Num'. 10* 0.97 ±0.16 1.01 ±O.lB 0.99±0.15 1.00 ± 0.19 NS NSfibre’ Other traits Age, d 149 ±8 155 ±8 149 ±7 154 ±8 ** ** LW, kg 97.3 ± 5.0 97.1 ± 3.8 97.7 ± 4.4 96.7 ± 4.7 NS NS ADG.g 937 ±62 929 ±66.1 960 ±60.7 910 ±67.8 NS ** CW, kg 71.3 ±4.1 71.7 ±3.2 71.4 ±3.4 71.4 ±4.0 NS NS pH, 6.28 ±0.24 6.41 ±0.23 6.36 ± 0.24 6.34 ± 0.25 ** NS pH 2 5.50 ± 0.09 5.51 ±0.13 5.51 ±0.13 5.50±0.10 NS NS CSAk)i|| (cm 2 ) 42.4 ±4.5 41.5 ±4.0 40.3 ± 3.3 43.4 ±4.5 NS ** M%,% 57.0 ± 2.7 56.6 ± 2.2 55.7 ± 1.9 57.7 ± 2.5 NS ** F%, % 20.0 ±3.2 20.0 ±3.0 21.4 ±2.6 18.9 ±3.1 NS ** NS =not significant, p>0.05; * = significant, p<0.05; ** = significant, pl' CSA 118 .222 .148 .045 .202 .046 .060 .114 .060 -.143 � * CSA,. .235 .160 .062 .223 .023 .038 .092 -.090 -.169 fibre � * Num,.. -.103 .008 -.005 .046 -.012 .001 .493 -.305 .391fibre *** *** *** * = significant, p<0.05; *** = significant, p0.05). Nor was our study able to confirm the finding of Miller et al. (1975) that faster grow- ing pigs appeared to possess more, but smaller, fibres in longissimus than did slower growing pigs at the same live weight. We did, however, find a positive correlation between 1% . andr number LW (p<0.05) and between CSAi|a and LW (p<0.00l), and between CSA I(a and CW (p<0.001) and between CSA |m and CW (p<0.05). We also found a negative correlation between lIA% , (p<0.05) and CW. The positive corre-number v ‘ ' r lation between live weight and ADG (r=.414, p<.001) makes it difficult to come to any defi- nite conclusion regarding the relationship be- tween histochemicalparameters and growthrate. Some researchers have found a positive correla- tion between the percentage of type 118 fibres in longissimus and the CSA of pork loin (Bader 1981, Fiedler and Otto 1982,Wegner and Ender 1990,Fewson et al. 1993), but we could not con- firm this finding (p>0.05). Our findings were, however, consistent with those of Staun (1972) and Miller et al. (1975), namely that a positive correlation exists between the Num,. andfibre CSA |oin and between the Numtlbre and M%. A neg- ative correlation was found between Num rk andfibre F%. Conclusions Comparisons of all histochemical traits reveal significant variance between animals. Landrace longissimus shows a lower number of type 118 fibres with a larger fibre CSA than does York- shire longissimus. The CSA of type 118 fibres is larger in gilts than in castrates. There are differ- ences in growth and carcass parameters between the sexes. The large variation in histochemical and other traits between animals suggests that it should be possible to select animals with the desired characteristics for breeding. Further in- vestigations are needed to establish the criteria for good meat quality parameters and the herita- bility of these properties. References Bader, R. 1981. Enzymhislochemische, histometrische, histologische und elektronenmikroskopische Untersu- chungen an der Skelettmuskulatur gesunder aus- gemästeter Schweine der deutschen Landrasse in un- terschiedlichen Haltungssystemen. Berlin, Freie Univer- sität, Fachbereich Veterinärmed. 192 p. Diss. - 1983. Vergleichende histometrische und histologische Untersuchungenan der Skelettmuskulatur von Wild- und Hausschweinen. Berliner und Munchener Tierärztliche Wochenschrift 96: 89-97. Brooke, M. H. & Kaiser, K. K. 1970. Muscle fibre-types: How many and what kind? Archives of Neurology 123: 369-379. Dwyer, C.M., Fletcher, J.M. & Stickland, N.C. 1993 Muscle cellularity and postnatal growth in the pig. Jour- nal Animal Science 71: 3339-3343. Essen-Gustavsson, B. & Fjelkner-Modig, S. 1985. Skeletal muscle characteristics in different breeds of pigs in relation to sensory properties of meat. Meat Science 13: 33-47. - , Karlström, K. & Lundström, K. 1992. 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Miller, L.R., Garwood, V.A. & Judge, M.D. 1975. Fac- tors affecting porcine muscle fibre type, diameter and number. Journal Animal Science 41: 66-77. Nurnberg, K. & Ender, K. 1990. Die Fettqualität bei Schweinen unterschiedlichen Geschlechtes. Fleischwirt- schaft 70: 1099-1102. Oksbjerg, N., Blackhaw, A., Henckel, P., Fernandez, J. A. & Agergaard, N. 1990. Alterations in protein accre- tion and histochemical characteristics of the M. longis- simus dorsi in pigs caused by Salbutamol (a (3-adrenergic agonist). Acta Agriculturae Scandinavica 40: 397-401. Rede, R., Pribisch, V. & Rahelic, S. 1986. Untersu- chungen über die Beschaffenheit von Schlachttierkörpern und Fleisch primitiver und hochselektierter Schwei- nerassen. Fleischwirtschaft 66: 898-907, SAS Institute. 1990. SAS/STAT User's Guide, Version 6, Fourth Edition. SAS Institute Inc., Cary, N.C. Sosnicki, A. 1987. Histopathological observation of stress myopathy in M. longissimus in the pig and the re- lationship with meat quality, fattening and slaughter traits. Journal of Animal Science 65: 584-596. Staun, H. 1972. The nutritional and genetic influence on number and size on muscle fibres and their response to carcass quality in pigs. World Review of Animal Produc- tion 8: 18-26. Swatland, H.J. 1975. Relationship between mitochon- drial content and glycogen distribution in porcine muscle fibres. Histochemical Journal 7: 459-469. - 1977. Histochemical changes during muscle growth in pigs. Zentralblatt fur Veterinärmedizin, A. 24: 248-251. Tornberg, E., Andersson, A., Göransson, Å. & von Seth, G. 1993. Water and fat distribution in pork in rela- tion to sensory properties. In: Puolanne, E. et al. (eds.). Pork Quality: Genetic and Metabolic Factors. Papers pre- sented at an OECD workshop in Helsinki, Finland, June 8-10, 1992. p. 239-256. Wegner, J. & Ender, K. 1990. Mikrostrukturelle Grund- lagen des Wachstums von Muskel- und Fettgewebe und die Beziehung zu Fleischansatz und Fleischbeschaffen- heit. Fleischwirtschaft 70: 337-340. 599 AGRICULTURAL AND FOOD SCIENCE IN FINLAND Ruusunen, M. et al. Composition and cross-sectional area ofmusclefibre types SELOSTUS Lihassolutyypin ja lihassolun poikkipinta-alan yhteys sian kasvuun ja ruhon koostumukseen maatiaisessa ja yorkshiressa Tutkimuksessa verrattiin maatiais- ja yorkshire-sika- rotuja keskenään määrittämällähistokemiallisesti lon- g(ijim«i-lihaksen lihassolutyyppien ominaisuuksia. Lisäksi selvitettiin histokemiallisten ominaisuuksien suhdetta eläimen kasvuun ja ruhon laatuun. Käsitel- tävinä muuttujina olivat ikä, päiväkasvu, elopaino, teuraspaino, pH,-ja pH 2 -arvot, ulkofileen poikkipin- ta-ala sekä ruhon liha- ja rasvaprosentit. Lihassolut määritettiin myosiini ATPaasimenetelmällä ja luoki- teltiin kolmeen ryhmään: I, lIA ja 118. Lihassolujen lukumäärä laskettiin jakamalla fileen poikkipinta-ala keskimääräisellä lihassolun poikkipinta-alalla. Maatiaisen longissimus- lihaksessa oli tyypin 1 li- hassolujen poikkipinta-ala pienempi ja tyypin HB li- hassolujen poikkipinta-ala suurempi kuin yorkshiren /o/!£/.v,v/mn.v-lihaksessa. Leikkojen sessa tyypin 118 lihassolut olivat suurempia kuin imisien longissimus- lihaksessa. Rotuja sukupuoli ei- vät vaikuttaneet ulkofileen lihassolujen määriin. Maa- tiaisessa olivat alhaisempia kuin york- shiressa. Imisissä oli ruhon lihamäärä suurempi ja rasvamäärä pienempi kuin leikoissa. Myös ulkofileen poikkipinta-ala oli imisissä suurempi kuin leikoissa. Eri eläinyksilöiden histokemialliset, kasvu ja ruhon laatuominaisuudet vaihtelivat paljon. Histokemialli- set ominaisuudet eivät vaikuttaneet eläimen kasvuun ja ruhon laatuominaisuuksiin. 600 AGRICULTURAL AND FOOD SCIENCE IN FINLAND