Fatty acid composition of muscle fat and enzymes of storage lipid synthesis in whole muscle from beef cattle.

Enhanced intramuscular fat content (i.e., marbling) in beef is a desirable trait, which can result in increased product value. This study was undertaken with the aim of revealing biochemical factors associated with the marbling trait in beef cattle. Samples of longissimus lumborum (LL) and pars costalis diaphragmatis (PCD) were taken from a group of intact crossbred males and females at slaughter, lipids extracted, and the resulting FAME examined for relationships with marbling fat deposition. For LL, significant associations were found between degree of marbling and myristic (14:0, r = 0.55, P < 0.01), palmitic (16:0, r = 0.80, P < 0.001), stearic (18:0, r = -0.58, P < 0.01), and oleic (18:1c-9, r = 0.79, P < 0.001) acids. For PCD, significant relationships were found between marbling and palmitic (r = 0.71, P < 0.001) and oleic (r = 0.74, P < 0.001) acids. Microsomal fractions prepared from PCD muscle were assayed for diacylglycerol acyltransferase (DGAT), lysophosphatidic acid acyltransferase (LPAAT), and phosphatidic acid phosphatase-1 (PAP-1) activity, and the results examined for relationships with degree of intramuscular fat deposition. None of the enzyme activities from PCD displayed an association with marbling fat content, but DGAT specific activity showed significant positive associations with LPAAT (r = 0.54, P < 0.01), total PAP (r = 0.66, P < 0.001), and PAP-1 (r = 0.63, P < 0.01) specific activities. The results on FA compositions of whole muscle tissues provide insight into possible enzyme action associated with the production of specific FA. The increased proportion of oleic acid associated with enhanced lipid content of whole muscle is noteworthy given the known health benefits of this FA.