The potential benefits of genetics and genomics to improve beef quality – a review

Intrinsic quality attributes of beef, and especially its tenderness, depend not only on post-mortem factors associated with meat ageing, but also on muscle characteristics of live animals, which themselves depend on genetic, nutritional and rearing factors. Different breeds or different genotypes of the same breed mainly differ by the characteristics of their connective tissue (content and solubility of collagen), content and composition of intramuscular fat and/or the characteristics of their muscle fibres (slow-oxidative, fast-oxidoglycolytic and fast glycolytic). These differences induce mainly differences in meat colour and cooking losses and, to a lesser extent, in flavour and tenderness of beef. Mutation in the myostatin gene induces generalized hypertrophy of muscles, promotes a glycolytic muscle fibre metabolism, and leads to decreased collagen and intramuscular fat contents which favour tenderness and dietary attributes. Simultaneously, however, lower intramuscular fat content is detrimental for flavour. The genetic variability is quite high for intramuscular fat content (marbling), moderate for tenderness and low for flavour and juiciness. The identification of polymorphisms in some key genes which determine characteristics of connective tissue or of muscle fibres has been reported because of their association with beef quality traits. Gene or protein expression profiling thanks to the advent of functional genomics has also allowed the identification of new molecular indicators of tenderness or marbling. Generally, genetic selection in favour of high muscle development and low fat deposition induces an orientation of muscle fibres towards the fastglycolytic type as demonstrated by biochemical and functional genomic studies. Cited are 64 references.