Fresh meat quality is greatly determined through biochemical changes occurring in the muscle during its conversion to meat. These changes are key to imparting a unique set of characteristics on fresh meat, including its appearance, ability to retain moisture, and texture. Skeletal muscle is an extremely heterogeneous tissue composed of different types of fibers that have distinct contractile and metabolic properties. Fiber type composition determines the overall biochemical and functional properties of the muscle tissue and, subsequently, its quality as fresh meat. Therefore, changing muscle fiber profile in living animals through genetic selection or environmental factors has the potential to modulate fresh meat quality. We provide an overview of the biochemical processes responsible for the development of meat quality attributes and an overall understanding of the strong relationship between muscle fiber profile and meat quality in different meat species.

The objective of this study was to establish the developmental pattern and tissue specificity of porcine myostatin expression and to evaluate expression in skeletal muscle during circumstances in which muscle growth was altered. Northern blot analysis revealed two transcripts (1.5 and 0.8 kb). Myostatin mRNA was detected in whole fetuses at 21 and 35 days and was markedly increased (P < 0.05) by 49 days. At birth, mRNA abundance in longissimus muscle had declined significantly (P < 0.05) from that atday 105 of gestation and continued to decrease (P < 0.05) to its lowest level 2 wk postnatally (4 kg body wt). Myostatin expression was higher (P < 0.05) at 55, 107, and 162 kg body wt than at 4 kg body wt. Postnatally, myostatin mRNA was detected in skeletal muscle and mammary gland. Expression at birth was 65% higher (P < 0.04) in longissimus muscle of low-birth-weight piglets (0.57 ± 0.052 kg body wt) vs. normal (1.37 ± 0.077 kg body wt) littermates, irrespective of gender. However, suppression of longissimus muscle growth by food deprivation (3 days) did not alter (P > 0.15) myostatin expression in either 4- or 7-wk-old piglets. Additionally, myostatin mRNA abundance was not changed by porcine growth hormone administration in growing animals. These data indicate that myostatin expression in skeletal muscle peaks prenatally and that greater expression is associated with low birth weight. Expression in mammary gland indicates a possible role for myostatin in mammary gland development and/or lactation.