The influence of porcine growth hormone on muscle fibre characteristics, metabolic potential and meat quality

Treatment of lean female pigs with porcine growth hormone (placebo or 80 μg pGH per kg body weight per day) for 6 weeks from 50 kg to 86 kg body weight did not change the frequency and the percentage area of muscle fibre types (ST, FTa and FTb fibres) and muscle capillarity of M. longissimus dorsi, M. gluteus medius and M. psoas major. The mean fibre cross-sectional area increased 5·3%, albeit nonsignificantly, corresponding to a 6·6% increase in carcass meat. The muscles contained slightly less dry matter and protein, and the lipid content of M. longissimus dorsi decreased 19% after pGH treatment. In the backfat the fatty acid composition changed towards a higher ratio of polyunsaturated to saturated fatty acids. The pH_u of M. longissimus dorsi was unaltered, while the pH₄₅ was reduced by pGH. The muscle glycogen level and the activity of lactate dehydrogenase (LDH), citrate synthetase (CS), and 3-OH-acyl-CoA-dehydrogenase (HAD) of M. longissimus dorsi were unchanged by pGH. The haem pigment, shear force, sarcomere length and eating quality of loin chops, were unaffected by pGH treatment. The results show that pGH treatment did not change the muscle characteristics in a way that affects the meat quality of M. longissimus dorsi in lean female pigs.