[Electronmicroscopic findings in the skeletal muscles of newborn swine with congenital splayleg].

Pathomorphological studies were taken of 104 muscle samples (including M. longissimus dorsi, adductor, semimembranaceus) obtained from 26 piglets, aged between one and three days and received from six stocks (large whites, land race, hybrids), which exhibited symptoms of congenital splayleg. Presence of myofibrillar hypoplasia or disseminated necrotisation of fibre was established by light microscopy. Some of the piglets, however, failed to exhibit substantive changes at all. Four types of fibre were differentiated by electron microscopy: (1) the normal type (with intact fibrils, plenty of lipids etc.), (2) the hypoplastic type (inhibition of protein synthesis, lack and immaturity of fibrils, disorder of paraplasmatic substances), (3) the dystrophic type (variable defects of fibrils, decay), (4) the primitive type (myoplastlike cell elements with precipitate fibrillogenesis). While those types were of variegated intramuscular occurrence, some predominance was established of dystrophic changes. Hence, spraddle-legged piglets seem to be afflicted with disorder of muscular development accompanied by signs of myopathy. Outbreak and intensity of clinical symptoms are believed to depend on exogenous factors.