Energy metabolism in skeletal muscle of meat-producing animals

Abstract

In meat-producing animals, skeletal muscle is a tissue of major economic importance. Its main physiological functions are thermogenesis, posture and physical activity. Each of these and muscle growth present specific energy requirements, which may be responsible for competitions between the different metabolic pathways of the utilisation of energy-yielding nutrients. These metabolic regulations modify the efficiencies of ATP production and utilisation, as well as some muscle characteristics which are essential for meat quality. For example, a more glycolytic muscle metabolism is associated with a better utilisation of glucose, a higher sensitivity of muscle to insulin, an increased muscle development, a reduction in its energy expenditure and an increase in its glycogen content. Improvement of muscle growth through genetic selection induces a less oxidative muscle metabolism associated with a lower intramuscular lipid content. A rise in the supply of energy-yielding nutrients is in favour of protein, glycogen and intramuscular lipid deposition. Nevertheless, an excess in energy may be responsible for an enhanced resistance of muscle to insulin which then favours carcass adiposity. The turnover and the partition of nutrients among the intramuscular anabolic (lipogenesis, glycogenesis) and catabolic (glycolysis, lipolysis, oxidation) pathways remain to be investigated. Physical activity of animals and cold adaptation modify muscle characteristics in favour of oxidative metabolism. The issue which remains to be addressed today is to determine whether the optimisation of the efficiency of ATP production and utilisation is compatible with the improvement of meat quality, especially through its glycogen and intramuscular lipid contents.