Genetic comparison of the fatty acid composition of intramuscular and adipose tissue lipids from early and late maturing beef cattle

The Jersey breed of cattle is known to mature and deposit intramuscular fat earlier than the Limousin. For selection purposes, it is important to determine if the fatty acid compositions of their intramuscular and adipose tissues also differ. Therefore, the objective of this study was to compare the fatty acid compositions of total lipids (TL), phospholipids (PL) and triacylglycerol (TG) components in Jersey and Limousin cattle. Subcutaneous adipose and muscle tissues were biopsied between the 12th and 13th ribs of 30 grass-fed, non-lactating Jersey and Limousin cows which were part of the J.S. Davies Cattle Gene Mapping herd in South Australia. Lipid extraction, methylation and fatty acid separation and analyses were conducted by gas-liquid chromatography. GLM procedures in SAS were utilised to fit a model that included the fixed effects of genotype, tissue component and a two-way interaction on fatty acid composition, and pairwise comparison of interaction means was carried out using t-test. Jersey cows had more oleate (18:1n-9) and vaccenate (18:1n-7) than Limousins in their muscle phospholipids and this difference was also reflected in their total monounsaturated fatty acids (MUFA). Limousin cows on the other hand had more linoleate (18:2), arachidonate (20:4), eicosapentanoate (20:5) and this was reflected in their total polyunsaturated fatty acids (PUFA). In the triacylglycerol component of adipose tissue, differences in individual fatty acids were not significant. Total lipid composition of the muscle showed a similar pattern of breed differences to that earlier portrayed by the phospholipid component. It was concluded that Jersey cattle deposit significantly more monounsaturated fatty acids in the muscle. Limousin cattle on the other hand, have a higher proportion of polyunsaturates in muscle lipid, chiefly because the phospholipids of their muscle contain 10% more PUFA than the jersey. Also, analysis of either the PL or TL component is sufficient in reflecting the fatty acid composition of the muscle tissue, leanness is indicated by a similar PL and TL compositions whereas similarity between the TG and TL indicates a richness in fat. In this study, both breeds were lean