Abstract
In this review we first discuss the role of intramuscular fat as a factor affecting consumer preferences for meat and particularly beef. The development of intramuscular fat in beef cattle is then highlighted and where informative, examples from other species are used to highlight the importance of total carcase fatness and muscularity. The role of gene marker assisted selection for intramuscular fat is discussed in relation to changing fat distribution towards this site. Critical developmental time periods are proposed based on traditional growth studies along with new evidence from gene expression experiments using micro array analysis. Our current level of knowledge relating to metabolic and genomic aspects of fat metabolism in intramuscular adipocytes is discussed particularly with reference to glucose metabolism and regulatory genes. It is concluded that there is a growing body of evidence that intramuscular adipocytes are metabolically different to other depots (subcutaneous fat) and further research is needed to see if this offers the possibility for targeted stimulation of fat development within muscle.