Influence of growth promoting implants on fatty acid composition including conjugated linoleic acid isomers in beef fat

The influence of the growth promoting implants Synovex (SYN), Ralgro (RAL), and Revalor (REV) on the fatty acid profiles of subcutaneous fat, intramuscular fat, and phospholipids of 32 beef steers (eight steers per treatment, and eight controls) was studied. Fatty acid compositions and profiles of conjugated linoleic acid (CLA) isomers were determined by a combination of GC and triple-column Ag+-HPLC. Only small differences could be observed between the different treatment groups. The amount of saturated fatty acids relative to monounsaturated fatty acids was increased by all growth promoting implants in subcutaneous fat (P < 0.1) and also by SYN in intramuscular far. RAL led to slightly higher amounts of trans fatty acids in subcutaneous and intramuscular fat (P < 0.1). REV-implanted steers showed some significant differences in their profiles of polyunsaturated fatty acids compared to control steers. CLA content and isomeric distribution in subcutaneous fat were affected by SYN, which reduced amounts of total CLA (0.42 mg/g fat vs. 0.53 mg/g in control steers, P < 0.001) and decreased the proportions of the primary 18:2 c9t11 isomer (73% of total CLA for SYN vs. 77-78% for all other treatment groups). Slight increases of c9t11 CLA in intramuscular fat were observed in RAL- and REV-implanted steers (P < 0.1). Most differences in fatty acid composition observed in this study were probably due to shifts in the storage lipid/membrane lipid ratio.