Pathological Changes in the Microstructure of longissimus lumborum Muscle from Five Breeds of Pigs

Agricultural University of Kraków, Department of Reproduction and Animal Anatomy, Mickiewicza 24/28, 30-059 Kraków, Poland.
Folia Biologica (Impact Factor: 0.88). 01/2012; 60(1-2):55-60. DOI: 10.3409/fb60_1-2.55-60
Source: PubMed


The aim of the study was to determine the extent of histopathological changes in m. longissimus lumborum of PL, PLW, Duroc, Pietrain, and Puławska pigs (N = 30 per breed) aged 210 days. Changes in fibre size (atrophy, hypertrophy - giant fibres), changes in fibre shape (angular fibres), degenerative lesions (necrosis with phagocytosis) and connective tissue hypertrophy were evaluated. The percentage of individual pathological changes in m. longissimus lumborum of the analysed pig breeds was relatively low. Significantly more normal fibres were found in the muscles of Puławska compared to Pietrain pigs. Muscle fibre atrophy was the most frequent and extensive histopathological change. The muscles of Puławska pigs had significantly fewer atrophic, giant and angular fibres, significantly less necrosis with phagocytosis, and less animals with connective tissue hypertrophy compared to the other pig breeds. On the other hand, Pietrain pigs were characterized by a greater number of animals with giant fibres and a significantly higher proportion of giant fibres compared to the other breeds. Also the diameter of giant fibres was the largest in Pietrain, intermediate in PL and PLW, and the smallest in Duroc and Pulawska pigs. Moreover, current findings indicate that giant fibres may arise from each muscle fibre type (I, IIA and IIB). It is concluded that selection of pigs for increased leanness contributes to the incidence of histopathological changes, which may decrease pork quality.

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    ABSTRACT: Based on literature date and on their own experiences, the authors present the morphology, development and growth of the striated muscle, and the role of giant and splitting muscle fibers, and the mechanism of muscle splitting. The muscle develops from the myotom, the myoblasts become coherent myotubules, which then differentiate into muscle fibers. The longitudinal growth of the muscle fibers can take place through the elevation of the number of the sarcomeres or through their prolongation; however the exact mechanism of the morphological and structural changes in the skeletal muscle and myofibrils in the postnatal period is not clearly understood. Recent literature data suggests that postnatal growth of muscle can take place through the splitting of the giant muscle fibers. The presence and splitting of the giant muscle fibers seems to be related to the pathologic metabolism of the muscle, but their presence was detected also in normal muscles. The histological grading system, developed by the authors that provides an opportunity to define the stages (G1–G4) of split muscle fibers may be useful in the future also in the veterinary practice.
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