The relationship between microstructure of Longissimus lumborum muscle and carcass quality of bulls slaughtered at three ages

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1 Animal Science Papers and Reports vol. 24 (2006) no. 1, Institute of Genetics and Animal Breeding, Jastrzębiec, Poland The relationship between microstructure of Longissimus lumborum muscle and carcass quality of bulls slaughtered at three ages Krzysztof Młynek 1, Gabriela Elminowska-Wenda 2, Piotr Guliński 1 1 Departament of Cattle Breeding and Milk Evaluation, University of Podlasie, B.Prusa 14, Siedlce, Poland 2 Department of Histology, Chair of Animal Bioengineering, Technical-Agricultural University, Mazowiecka 28, Bydgoszcz, Poland (Received December 20, 2005; accepted February 15, 2006) The effect of age at slaughter (465, 568 and 711 days) on carcass quality (EURO score) and microstructure of Longissimus lumborum muscle (LL) were investigated in young crossbred bulls (Black-and-White Limousine and Black-and-White Charolaise, n=16 and 32, respectively). Moreover, the analysis concerned the effect of microstructure on carcass quality. Increasing age at slaughter positively affected the EUROP carcass evaluation score, rising from 2.1 in youngest to 3.7 points in the oldest bulls. Muscle fibres in oldest bulls were of greatest area (8457 µm 2 ). Closest relationship with muscle fibre area was shown by the age of slaughtered bulls (r=0.95**) and slightly lower by the carcass evaluation score (r = 0.75**). In LL of oldest animals the so called giant fibres appeared manifesting significantly larger area up to µm 2. KEY WORDS: bulls / carcass / microstructure / muscle fibres / slaughter value Year by year, increasing expectations of customers concerning beef quality, must be considered in relation to intensity of production. In that process, the age, feeding, breed and sex of animals are crucial factors, determining the slaughter value of fattened animals and quality of their meat [Wilton and Goddard 1996]. Age of animals at slaughter influences carcass quality traits and simultaneously affects meat tenderness and colour [Maltin et al. 1998, Renand et al. 2001]. Moreover, it significantly alters histological traits of a muscle, which are crucial for meat quality 57

2 K. Młynek [Handel and Strickland 1986, Kłosowski and Kłosowska 1993, Harper 1999, Klont et al Meat cattle breeding programmes that include these traits, should satisfy both the producers (in their financial relations with meat plants) and the customers, referring to culinary traits of beef [Renand et al. 2001]. This research aimed at determining the effect of the slaughter age of young fattening bulls on (i) quality of their carcasses and (ii) microstructure traits of Longissimus dorsi (pars lumborum) muscle (LL). Additionally, correlation coefficients were estimated between carcass selected traits and carcass weight and histological structure of LL. Material and methods Material consisted of 48 young fattening bulls, offspring of Black-and-White dams mated to Limousine or to Charolaise sires (16 and 32 crossbred offspring, respectively). Animals were kept in tie-in stalls and fattened with farm-made feeds. Three age groups of bulls at slaughter were considered: I up to 500 days (n=15), II from 501 to 600 days (n=19), and III over 600 days (n=14). Within 30 min post-mortem, samples were excised from Longissimus dorsi (pars lumborum) muscle (LL) for histological analysis and instantly frozen in a liquid nitrogen. Histological analyses were performed according to Kłosowski and Kłosowska [1988]. Histo-chemical reactions, differentiating muscle fibres into STO ( red ), FTO + FTG ( intermediate ) and white ones, were conveyed according to combined Ziegan method [1979]. Basic staining H+E was also performed. In 10 randomly chosen fibre bundles/sheaves (with no reference to the type of fibre) area of muscle fibres was measured with Multi Scan programme. Evaluation of meat deposition rate (meat content) of carcasses was performed according to EUROP scoring system (E = 5 points, P = 1 point) on warm carcasses, as stated in the respective meat plant regulations. Evaluation of carcass traits was performed after 24-hour chilling at +4 C. Statistical evaluation of results was performed with a one-way analysis of variance and involved 3 age groups of animals. Moreover, Pearson linear correlation coefficients between LL microstructure traits and slaughter quality indicators in three age groups were estimated. The differences between groups were evaluated with Duncan test. 58 Results and discussion LL microstructure traits in bulls from three age groups of commercial crosses (Black-and-White Limousine and Black-and-White Charolaise crosses pooled), are shown in Table 1. Increasing age at slaughter was significantly related to increasing muscle fibres area. In youngest bulls (group I) which were slaughtered at age of 465 days (Tab. 2) the area of muscle fibres was µm 2 (Tab. 1). In bulls slaughtered at the age of 568 days (group II) the muscle fibres area was by 1533

3 Muscle microstructure and carcass quality of bulls Table 1. Microstructure of Longissimus lumborum muscle in bulls slaughtered at different ages (crossbreds pooled) Group Mean fibre area (µm 2 ) STO ( red ) Per cent of fibres FTO + FTG ( intermediate + white ) I (n=15) 3566 a A A II (n=19) 5099 Ab Ba Ba III (n=14) 8457 B b b aa Means in columns with different superscripts differ significantly at: small letters P 0.05; capitals P Table 2. Slaughter parametres in bulls slaughtered at different ages (crossbreds pooled) Group Age (days) Carcass weight (kg) EUROP grade (muscling) I (n=15) 465 A a A II (n=19) 568 B a b III (n=14) 711 C b Ba aa Means in columns with different superscripts differ significantly at: small letters P 0.05; capitals P

4 K. Młynek µm 2 greater than in group I. In the oldest bulls, i.e. those slaughtered at the age of 711 days (group III), the muscle fibres area was by 3358 µm 2 greater than in group II. In LL of the oldest animals giant muscle fibres were observed. Their typical trait is big area [Handel and Strickland [1986]. In the present study this was illustrated by the presence of fibres reaching up to 25,208 µm 2 (Tab. 1, Photo 1). Along with decreasing bulls age, the share of fibres with oxidative activity ( red fibres) decreased, accompanied by increasing share of fibres with glycolytic transformation ( intermediate + white fibres). Photo 1. Cross-section of Longissimus dorsi muscle in 22-months old Black-and-White Charolaise bull. G giant fibres. In muscles of crossbreds from group I the share of red fibres reached 23.5% and that of intermediate + white 76.5%. (Tab. 1). In the oldest animals (group III) the respective proportions were 30.9 and 69.1%. Bigger differences, however in the group of younger animals (slaughtered at the age from 180 to 480 days) were observed by Bellman et al. [2004] and, close to the present results, by Kłosowski and Kłosowska [1988]. Similar results concerning the area and share of muscle fibres in bulls with carcass weight ranging from 157 to 322 kg and the age from 221 to 485 days were reported by Vestergaard et al. [2000]. According to Maltin et al. [1998], muscle fibres area in cattle increases with animals age. Positive effect of age at slaughter was observed on carcass weight and conformation. Within the EUROP classification, carcasses from group I bulls were scored to 2.1 points while heavier carcasses from group II and III, with bigger weight ( and kg) to 3.1 and 3.7 points (Tab. 2). In the oldest animals (group III) where muscle fibres had biggest area (Tab. 1), better classification results (EUROP 3.7 points) and biggest carcass weight 335,4 kg (Tab. 2) were noted. Similar trends were described by May et al. [1992], Jones and Tatum [1994] and Młynek and Litwińczuk [2001]. 60

5 Muscle microstructure and carcass quality of bulls In Table 3 correlation coefficients are presented describing relations between carcass quality indicators, LL muscle fibre area and bulls slaughter age. LL fibre area showed highest correlation with the age of slaughtered bulls (0.95**). Lower correlation coefficients were identified between LL fibre area and carcass conformation score or between bulls age and carcass weight (0.75** and 0,69**, respectively). Detailed results of correlation analysis concerning carcass quality traits and LL microstructure as related to age groups examined, are presented in Table 4. Positive correlation coefficients and increase in their values with increasing age were observed, concerning carcass weight and LL fibres area. The coefficients varied from 0.44* in case of group I, to 0.57* in group III and 0.59* in group II. Analysis of results concerning carcass conformation (EUROP) proved least correlations in groups II and III (0.55*) and slightly higher in group I (0.58*). Renand et al. [2001] found positive correlation coefficients, reaching 0.37*, between muscle fibres area and age of young bulls slaughtered between week 64 and 82 of fattening. Similar results, at the level of 0.34*, between muscle microstructure traits and the age of animals, slaughtered in month 10 and 16 of life, were described by Seideman and Crouse [1986] who observed the increased area of muscle fibres with increasing age of animals. Similar relations were described by Jurie et al. [1995] and Bellman et al. [2004]. To summarize, it Table 3. Correlation coefficients (r) between Longissimus lumborum muscle fibres area and age and carcass weight and quality in bulls (ages pooled) Trait n Mean Min. Max. age (days) r carcass weight EUROP grade (muscling) Fibre area (µm 2 ) ** 0.59** 0.75** Age ** 0.72** **P Table 4. Correlation coefficients (r) between Longissimus lumborum muscle fibre area and carcass weight and quality in bulls as related to age Trait Age group age (days) r carcass weight EUROP grade (muscling) Fibre area (µm 2 ) I (n=15) II (n=19) III (n=14) 0.69** 0.78** 0.79** 0.44* 0.59* 0.57* 0.58* 0.55* 0.55* *P 0.05; **P

6 K. Młynek can be stated that positive effect of progressing age was observed in case of carcass weight and conformation. Despite positive relations between these traits and muscle microstructure, it must be emphasized that increased slaughter age negatively affected histological traits through increased muscle fibres area. The results presented here show that slaughtering young bulls, crossbreds with Charolaise and Limousine breeds, at the age of over 600 days enables obtaining carcasses of better quality. However, what is a disadvantage, it promotes incidence of pathological, much thicker giant fibres. It can be concluded that increased size of fibres in older animals is related to increased carcass weight and affects carcass muscle deposition significantly. REFERENCES 1. Bellmann O., Wagner J., Teuscher F., Schneider F., Ender K., 2004 Muscle characteristics and corresponding hormone concentrations in different types of cattle. Livestock Production Science 85, Handel S.E., Strickland N.C., 1986 Giant muscle fibres in skieletal muscle of normal pigs. Journal of Comparative Pathology V.96, Harper G.S., 1999 Trends in skeletal muscle biology and the understanding of toughness in beef. Australian Journal of Agricultural Research 50, Jones B.K., Tatum J.D., 1994 Predictors of beef tenderness among carcasses produced under commercial conditions. Journal of Animal Science 72, JURIE C., ROBELIN J., PICARD B., GEAY Y., 1995 Post-natal changes in the biological characteristics of semitendinosus muscle in male Limousine cattle. Meat Science 41, Klont R.E., Barier V.M.H., Smulders F.J.M., Van Dijk A., Hoving-Bolink A.H., Eikelenboom G., 1999 Post-mortem variation in ph, temperature and colour profiles od veal carcasses in relation to breed, blood haemoglobin content and carcass characteristics. Meat Science 53, Kłosowski B., Kłosowska D., 1988 Veranderungen der Eigenschaften der Muskelfasern in M. Longissimus dorsi in Abhangigkeit des alters derjungbullen der Schwarzbunten rasse. Karl- Marx-Universitat in Leipzig, Histologie und Embrologie, Wachstum und Postnatale Entwicklung, Kłosowski B., Kłosowska D., 1993 Zmiany w udziałach typów włókien mięśniowych m. Longissimus lumborum buhajków rasy NCB w okresie wzrostu. (Changes in the composition of the muscle fiber types in Longissimus lumborum muscle of the bulls of Black-and-White lowland breed during growth) In Polish, summary in English. Zeszyty Naukowe ATR w Bydgoszczy, 182 (23), May S.G., Dolezal H.G., Gill D.R., Ray F.K., Buchanan D.S., Effects of days fed, carcass grade traits and subcutaneous fat removal on postmortem muscle characteristics and beef palability. Journal of Animal Science 70, Maltin C.A., Sinclair K.D., Warriss P.D., Grant C.M., Porter A.D., Delday M.I., Warkup C.C., 1998 The effect of age at slaughter, genotype and finishing system on the biochemical properties, muscle fibre type characteristics and eating quality of bull beef from suckled calves. Animal Science, Młynek K., Litwińczuk Z., 2001 Influence of genotype and age of cattle on slaughter value and meat quality traits. Polish Journal of Food and Nutrition Sciences, (10/51), 3, Renand G., Picard B., Touraille C., Berge P., Lepetit J., 2001 Relationship between muscle characteristics and meat quality traits of young Charolaise bulls. Meat Science 59,

7 13. Seideman S.C., Crouse J.D., 1986 The effects of sex, condition, genotype and diet on bovine muscle fibre characteristics. Meat Science 17, Vestergaard M., Therkildsen M., Henckel P., Jansen L.R., Andersen H.R., Sejrsen K., 2000 Influence of feeding intensity, grazing and finishing feeding on meat and eating quality of young bulls and the relationship between muscle fibre characteristics, fibre fragmentation and meat tenderness. Meat Science 54, Wilton J.W., Goddard M.E., 1996 Selection for carcasses and feedlot traits cinsidering alternative slaughter and points and optimized management. Journal of Animal Science 74, ZiEgan J.; Kombinationen enzymhistochemischer Methoden zur Fasertypendiffer-enzierung und Beurteilung der skelettmuskulatur. Acta Histochemica 65, Krzysztof Młynek, Gabriela Elminowska-Wenda, Piotr Guliński Zależność między cechami mikrostruktury mięśnia najdłuższego grzbietu a jakością tuszy buhajów ubijanych w różnym wieku S t r e s z c z e n i e Badano wpływ średniego wieku przy uboju (465, 568 i 711 dni) na wyniki oceny jakości tuszy w skali EUROP i mikrostrukturę mięśnia longissimus lumborum (LL) buhajów mieszańców rasy cb z rasą limousine (n=16) bądź cb z rasą charolaise (n=32). Analizą objęto także zależność między cechami mikrostruktury LL a wynikami oceny jakości tuszy w skali EUROP. Wzrostowi wieku ubojowego towarzyszył wzrost jakości tusz od 2.1 do 3.7 pkt. Włókna mięśniowe buhajów najstarszych miały największą powierzchnię (8457 µm 2 ). Najściślejszą korelację stwierdzono między powierzchnią włókien mięśniowych a wiekiem, w którym ubijano buhaje (r=0,95**). Nieznacznie mniejsza korelacja (r = 0,75**) wystąpiła między powierzchnią włókien a jakością tusz ocenianych w systemie EUROP. W LL buhajów najstarszych stwierdzono obecność włókien zwanych olbrzymimi do µm 2. 63

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