Abstract
The effects of long-term application of recombinant porcine somatotropin (pST) on the development of muscle structure characteristics were examined in finishing pigs from about 120 to 200 days of age. Shot biopsy samples from the longissimus dorsi (longissimus) muscle of 60 Landrace barrows were taken at the initiation of treatment and again after 5 to 10 weeks treatment. The injection of 2 mg pST/d and 4 mg pST/d caused an intense hypertrophy of muscle fibres and resulted in 11% thicker muscle fibres at the end of treatment. In the course of fibre growth, dose-dependent differences occurred. The total muscle fibre number, calculated by muscle cross sectional area and fibre number per unit area of carcass samples, was not influenced. There was a tendency for more nuclei per fibre, whereas the nucleus-cytoplasm ratio seemed to be unchanged, Generally the composition of muscle fibre types (white, intermediate, red or αW, αR, βR) was not affected. In pST treatment groups, no more animals with giant fibres were found, nor were higher percentages of this structural anomaly in carcass muscle sections discovered.
Published Version
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