Original Paper

Muscle Growth and Fiber Type Composition in Hind Limb Muscles during Postnatal Development in Pigs
Veit Wank^a, Martin S. Fischer^b, Bernd Walter^c, Reinhard Bauer<sup>c

a</sup>Institute of Sports and Sports Science, Eberhard Karls University, Tübingen,
^bInstitute of Systematic Zoology and Evolutionary Biology and
^cInstitute of Molecular Cell Biology, Pathophysiology Lab, Friedrich Schiller University, Jena, Germany

Address of Corresponding Author

Cells Tissues Organs 2006;182:171-181 (DOI: 10.1159/000093966)

  Key Words

• Muscle fibers
• Muscle growth
• Postnatal development
• Skeletal muscle
• Pig

  Abstract

Rapid postnatal development in pigs is reflected by differentiation in skeletal muscle. This process depends on muscle function and demands, but a comprehensive overview of individual developmental characteristics of quickly growing leg muscles in pigs is still missing. This study focused on the development of 10 hind limb muscles in pigs. To determine these changes in mass, fiber type patterns and fiber diameters were analyzed 0, 2, 4, 7, 14, 28, 42, 56 and 400 days after birth. Generally, the proportion of slow fibers increased from birth to 8 weeks. Thereafter, only minor changes in muscle fiber type composition were observed. The majority of the muscles contained less then 10% slow-twitch fibers at birth, increasing to between 12 (Musculus vastus lateralis) and 38% (M. gastrocnemius medialis) in adult pigs. By contrast, postural muscles already had 20-30% slow fibers at birth, and this contribution increased up to 65% in adults (i.e. M. vastus intermedius). From birth to the 2nd week, only in slow fibers could activity of oxidative enzymes be detected. A differentiation of fast-twitch fibers into subtypes with high (comparable to type IIA) and low oxidative metabolism (equivalent to type IIB) occurred between the 2nd and 4th week of life. The ratio between type II fibers with high and low oxidative enzyme activity did not change markedly through development in any muscle, although there was a trend towards an increasing proportion of type IIA fibers in the soleus. In the majority of the muscles investigated, the fast-twitch fibers with low oxidative metabolism (IIB) obtained the largest cross-sectional area. In contrast, at birth no remarkable differences in the diameter of fast and slow fibers were found. The rapid increase in muscle mass compared to body mass reflects the high performance in meat production of the cross pig investigated.

Copyright © 2006 S. Karger AG, Basel

  Author Contacts

Dr. Reinhard Bauer
Institute of Molecular Cell Biology, Pathophysiology Lab
Friedrich Schiller University, Nonnenplan 2
DE-07740 Jena (Germany)
Tel. +49 3641 938956, Fax +49 3641 938952, E-Mail Reinhard.Bauer@mti.uni-jena.de

  Article Information

Accepted after revision: April 6, 2006
Number of Print Pages : 11
Number of Figures : 5, Number of Tables : 1, Number of References : 57