Myofibre typing and ontogenesis in farm animal species

Abstract

This paper synthetizes the studies carried out on myofibre typing and ontogenesis in the principal farm animal species since muscle fibre characteristics play a key role in meat quality. After a general description of muscle fibre characteristics and ontogenesis, four articles review the particularities of bovine, porcine, chicken and fish. In all species myofibre ontogenesis begins very early during embryonic life, with the appearance of two or three successive waves of myoblasts which constitute the origin of the different types of muscle fibres. In the largest species (bovine, pig) a third generation arises in the late foetal or early postnatal period. Following these two or three waves of myogenesis, the total number of fibres is fixed except in fish where hyperplasia occurs after birth. Contractile and metabolic differentiation proceeds by steps in parallel to myogenesis. In bovine, the main events of differentiation occur during foetal life, whereas they occur soon after birth in pig, poultry, but some plasticity remains later in life in all species. This comparative survey shows that the cellular processes of differentiation are comparable between species, while their timing is usually species specific.