Pathological changes in the structure of semimembranosus muscle from pigs included in the Stamboek and Torhyb breeding programmes

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1 Animal Science Papers and Reports vol. 24 (2006) Supplement 2, Institute of Genetics and Animal Breeding, Jastrzębiec, Poland Presented at the III Conference Genetic and environmental possibilities of adjusting the slaughter value and meat quality of animals to consumers requirements 7-8 September 2006, Lublin-Krasnobród, Poland Pathological changes in the structure of semimembranosus muscle from pigs included in the Stamboek and Torhyb breeding programmes Joanna Bogucka, Konrad Walasik, Gabriela Elminowska-Wenda, Monika Kruczyńska Department of Animal Biotechnology, University of Technology and Life Sciences in Bydgoszcz, Mazowiecka 28, Bydgoszcz, Poland The aim of the study was to determine the extent of histopathological changes in the semimembranosus muscle of crossbred pigs originating from the Dutch programme for Stamboek pigs and the Polish programme for Torhyb pig production. A total of 78 castrated males at approximately 105 kg body weight were included. Histopathological changes in the semimembranosus (SM) muscle of pigs were estimated based on microscopic preparations stained according to van Gieson s method. Analysis was made of changes in fibre size (fibre atrophy, hypertrophy giant fibres), changes in fibre shape (triangular, trapezoid and elongated fibres), degenerative changes of fibres (necrosis plus phagocytosis, fibre splitting), connective tissue hypertrophy and inflammatory infiltrations. The extent of pathological changes was expressed as per cent of 200 muscle fibres except connective tissue hypertrophy and inflammatory infiltrations, which were evaluated subjectively. The percentage of individual pathological changes in the SM muscle was low, with over 94% normal fibres in both crossbred groups studied. Muscle fibre atrophy was the most frequent histopathological 45

2 Joanna Bogucka et al. change observed. It was found in 100% of the Stamboek pigs and in 92.31% of Torhyb pigs. Torhyb pigs had significantly more giant fibres, possibly indicating their sensitivity to stress associated with variable environmental conditions. KEY WORDS: histopathological changes / muscle / pigs / semimembranosus muscle Long-term studies on the relationship between the histological structure of muscles and porcine meat quality allow a conclusion that an increase in the content of white fibres with glycolytic metabolism is accompanied by a more frequent incidence of PSE fault, and in highly-leaned pigs (Pietrain), by pathomorphological changes of muscle tissue [Kłosowska 1973, 1984; Kłosowska et al. 1995]. Breeders efforts aim at improving growth rate, feed conversion and lean content of pig carcass as well as at reducing the incidence of PSE and DFD meat, which markedly limit the technological properties of pork. In addition to genetic traits, environmental conditions exert a highly significant effect on the health status and production level of animals. Changes in these conditions, transport, high indoor temperature, exhaustion and slaughter itself may induce many abnormalities in muscle tissue structure. The morphological properties of muscle tissue and the extent of changes in the structure of this tissue are good indicators of meat quality. The aim of the present study was to determine the extent of histopathological changes in the semimembranosus muscle of crossbred pigs originating from the Dutch Stamboek programme and the Polish Torhyb programme. Material and methods A total of 78 castrated males representing Dutch Stamboek crossbreds and Polish Torhyb crossbreds (39 animals each) were examined. In the Stamboek programme, two-breed crossing was applied with the use of maternal lines (Polish Landrace PL) and maternal and paternal lines (Polish Large White PLW), according to the following scheme: PLW females (maternal line) PL males (maternal line) F 1 females PLW males (paternal line) fattening Torhyb crossbreds were obtained by simple three-breed crossing according to the following scheme: PLW females PL males F 1 females Pietrain males fattening 46

3 Adjusting the slaughter value and meat quality of animals to consumers requirements At the age of about three months the weaners weighing approx. 30 kg were included in the experiment and subjected to control fattening. up to approx. 105 kg body weight, under standard conditions. Prior to inclusion in the experiment, all the animals were individually tagged and weighed. Pigs were kept in group pens with animals per pen. Floor area was at least 1 m 2 per animal. Ad libitum feeding from automatic feeders was used. The nutritive value of the complete diet was 12.7 MJ metabolizable energy, 170 g crude protein and 10 g lysine/kg. The amount of feed offered was controlled. The semimembranosus (SM) muscle was subjected to histopathological analysis. Muscle samples were taken approx. 45 min post-slaughter, frozen in liquid nitrogen and stored until analysis. Samples were sectioned at 10 µm in a Leica cryostat at -25 C and stained using van Gieson s method [Dubowitz et al. 1973] to determine the presence of collagen and identify pathological changes in the muscle. Changes in muscle structure were evaluated in an area of mm 2 using a Q 500 MCP computer image analysis programme (Leica). The following types of histopathological changes in SM muscle were accounted for: changes in fibre size (fibre atrophy, hypertrophy giant fibres); changes in fibre shape (triangular, trapezoid and elongated fibres); degenerative changes of fibres (necrosis plus phagocytosis, fibre splitting); connective tissue hypertrophy; cell reactions leukocyte infiltrations (inflammatory infiltrations). The extent of histopathological changes was expressed as per cent. Analysis included 200 muscle fibres except connective tissue hypertrophy and leukocyte infiltration, which both were estimated subjectively according to the following scale: 0 no change; + minor change; + + major change. The numerical data were evaluated statistically using STATISTICA 5.5 PL software. Results and discussion The histopathological changes observed in the analysed pig SM muscle tissue included changes in fibre size (small fibres atrophic, giant fibres hypertrophic), changes in fibre shape (triangular, trapezoid and elongated fibres), and degenerative changes such as fibre splitting, fibre necrosis plus phagocytosis, connective tissue hypertrophy and leukocyte infiltrations (inflammatory infiltrations). Some of these changes are shown in Figures 1, 2 and 3. The share (%) of pigs with histopathological changes identified in the SM muscle is given in Table 1 and shows that most common was fibre atrophy. It was found in 100% of Stamboeks and in 92.31% of Torhybs. The 47

4 Joanna Bogucka et al. Fig. 1. Cross section of semimembranosus muscle. Fibre necrosis with phagocytosis (black arrow), fibre atrophy (red arrows) magnification. Fig. 2. Cross section of semimembranosus muscle.. Connective tissue hypertrophy (arrow) magnification. literature available contains little information on the evaluation of histopathological changes in the SM muscle of pigs. Bogucka and Kapelański [2004], who investigated animals described in the present report, found atrophy in the longissimus lumborum muscle of all the animals examined. Giant fibres, the formation of which is, according to many authors [Kłosowska 1973, 1984, Kłosowska et al., 1995, Sośnicki 1985], 48 Fig. 3. Cross section of semimembranosus muscle.. Giant fibre (arrow) magnification.

5 Adjusting the slaughter value and meat quality of animals to consumers requirements Table 1. Percentage of pigs showing histopathological changes in semimembranosus muscle Trait Stamboek Pig group Torhyb Fibre atrophy Giant fibres Changes in fibre shape Fibre necrosis and Phagocytosis Fibre splitting Connective tissue hypertrophy Inflammatory infiltrations no change. + minor change. ++ extensive change. associated with the sensitivity of animals to stress, were more common in Torhyb than in Stamboek pigs (53.85% vs 17.95%). Unfavourable environmental conditions lead to degenerative changes in the muscle such as fibre necrosis, which results in fibre splitting. It is often accompanied by appearing within the cell of leukocytes, lymphocytes, histiocytes and macrophages containing the remnants of split muscle fibres in their plasma. According to Hausmanowa-Petrusewicz [1993] and Kłosowska et al. [1998], this necrosis with phagocytosis is often accompanied by connective tissue hypertrophy. Fibre necrosis and phagocytosis were also observed by Kłosowska [1984] in the muscles of pigs exhausted by transportation as well as in the muscles of pigs rested. These changes are more extensive in exhausted and stressed animals. The current study shows that both fibre necrosis and connective tissue hypertrophy were more common in Torhybs, possibly indicative of their lower resistance to environmental conditions and poorer meat quality. Inflammatory infiltration was found in 2.56% of Torhyb, but in none of the Stamboek pigs. Changes in fibre shape (mostly resulting in triangular shape) and fibre splitting were less common in Torhybs. The frequency of histopathological changes in the SM muscle of two crossbred groups is presented in Table 2, which shows that a total of 5.05% pathological changes (and thus 94.95% normal fibres) were found in both groups. No significant differences were found between the analysed pig groups in the incidence of histopathological changes except muscle fibre hypertrophy. Significantly more giant fibres were 49

6 Joanna Bogucka et al. Table 2. Incidence of histopathological changes in the semimembranosus muscle Normal fibres (%) Atrophic fibres (%) Giant fibres (%) Trait Changes in fibre shape (%) Fibre necrosis and phagocytosis (%) Fibre splitting (%) Total changes (%) Stamboek b Pig group Torhyb a Means marked with different superscripts differ significantly at P<0.05. found in Torhybs (0.67%) than in Stamboeks (0.17%). This is in accordance with Kłosowska [1984], who reported the highest number of giant fibres to appear in the muscles of Pietrain pigs. The share of giant fibres was also large in Pietrain crosses. The presence of giant fibres demonstrates that these animals are highly sensitive to stress. Torhyb crossbreds were obtained by crossing white breeds with the Pietrain breed, which is considered the least resistant to variable environmental conditions. Likewise, Bogucka and Kapelański [2004] reported that giant fibres were much more common in the longissimus lumborum muscle of Torhyb than of Polish Landrace and Stamboek fatteners. Szmańko et al. [2002] concluded that giant fibres account for approximately 1% of all fibres, which was confirmed by the current study. It must be noted, however, that all of the changes were not very extensive although they occurred in most of the animals studied. Similarly, changes limited to single muscle bundles were observed by Walasik et al. [2000] in the longissimus lumborum muscle of Hampshire crossbreds. The results presented here can be summarized as follows. The percentage of individual pathological changes in the semimembranosus muscle was found low, with over 94% normal fibres identified in both groups of crossbreds. Fibre atrophy was the most common histopathological change of SM muscle, found in all of the Stamboek and in 92.31% of Torhyb pigs. The latter had significantly more giant fibres, possibly indicating their sensitivity to stress associated with variable environmental conditions. 50

7 Adjusting the slaughter value and meat quality of animals to consumers requirements References BOGUCKA J., KAPELAŃSKI W., 2004 Histopathological changes in m. longissimus lumborum of Polish Landrace pigs and Torhyb and Stamboek crossbreds. Animal Science Papers and Reports 22, Suppl. 3, DUBOWITZ W., BROOKE M., NEVILLE H.E., 1973 Muscle Biopsy: A Modern Approach., W. B. Saunders Company LTD London, Philadelphia, Toronto. HAUSMANOWA-PETRUSEWICZ I., 1993 Choroby mięśni (Muscle diseases). In Polish. PZWL, Warszawa. KŁOSOWSKA D., 1973 Czerwone i białe włókna w mięśniach różnych ras świń. (Red and white fibres of nuscles of different pig breeds). In Polish, summary in English. Zeszyty Problemowe Postępów Nauk Rolniczych. 139, KŁOSOWSKA D., 1984 Cechy histologiczne i histochemiczne mięśni świń, bydła i drobiu a jakość mięsa. (Histological and histochemical traits of muscles pigs, cattle and poultry) In Polish. Bydgoskie Towarzystwo Naukowe, Prace Wydziału Nauk Przyrodniczych Seria B, Rozprawy habilitacyjne (Thesis) 31, KŁOSOWSKA D., KLUCZEK J. P., KAPELAŃSKI W., 1998 Zmiany histologiczne tkanki mięśniowej determinowane warunkami środowiskowymi (Environmentally determined histological changes in the muscle tissue) In Polish. Bydgoskie Towarzystwo Naukowe, Prace Komisji Nauk Rolniczych i Biologicznych XXXII, Seria B, 44, KŁOSOWSKA D., KŁOSOWSKI B., NOWAK B., 1995 Histopathological changes in longissimus muscle of Pietrain pigs and its crosses. Proceedings of the 2 nd Dummerstorf Muscle Workshop on Muscle Growth and Meat Quality, Rostock, May, SOŚNICKI A., 1985: Histopatologiczna charakterystyka miopatii obciążeniowej m. najdłuższego (m. longissimus) u świń. Patologia Polska. 34(3), SZMAŃKO T., WYSKIEL S., GRAJEWCZYK P., 2002 Zależność między zdolnością utrzymania wody a budową histologiczną tkanki mięśniowej świń. (Relationship between water holding capacity and histological structure of muscle tissue in pigs). In Polish. with English summary. Prace i Materiały Zootechniczne, Zeszyt Specjalny 13, WALASIK K., KŁOSOWSKA D., GRZEŚKOWIAK E., 2000 Występowanie zmian patologicznych w musculus longissimus lumborum mieszańców świń z udziałem rasy hampshire. Roczniki Naukowe Zootechniki, Supplement 6, Joanna Bogucka, Konrad Walasik, Gabriela Elminowska-Wenda, Monika Kruczyńska Histopatologiczne zmiany struktury mięśnia półbłoniastego (m. semimembranosus) świń uzyskiwanych z programów Stamboek i Torhyb S t r e s z c z e n i e Celem pracy było określenie rozległości zmian histopatologicznych w mięśniu półbłoniastym (musculus semimembranosus) świń mieszańców z holenderskiego programu Stamboek i polskiego programu produkcji tuczników Torhyb. Materiał doświadczalny stanowiło 78 wieprzków o masie ciała 51

8 Joanna Bogucka et al. ca. 105 kg. Zmiany histopatologiczne w mięśniu oceniono na podstawie preparatów mikroskopowych wybarwionych metodą Van Giesona. Oszacowano zmiany wielkości włókien (atrofia, hipertrofia włókna olbrzymie), zmiany ich kształtu (trójkątne, trapezowate, wydłużone), zmiany degeneracyjne (martwica z fagocytozą, rozszczepienie), przerost tkanki łącznej oraz infiltracje leukocytarne. Rozległość zmian patologicznych wyrażono w procentach na 200 włókien mięśniowych z wyjątkiem przerostu tkanki łącznej i infiltracji leukocytarnych, których występowanie oceniono sposobem subiektywnym. Udział (%) poszczególnych zmian patologicznych w badanym mięśniu był niski, a w obu badanych grupach świń stwierdzono ponad 94% włókien prawidłowych. Najczęściej obserwowaną zmianą histopatologiczną w badanym mięśniu była atrofia włókien mięśniowych. Obserwowano ją u wszystkich osobników z programu Stamboek i u 92,31% osobników z programu Torhyb. W mięśniach świń z programu Torhyb stwierdzono istotnie więcej włókien olbrzymich niż w mięśniach świń z programu Stamboek, co może świadczyć o wrażliwości tych zwierząt na stres związany ze zmiennymi czynnikami środowiskowymi. 52