Chromatographic analysis of 18:1 isomers in blended feed-grade fats used in poultry diets.

The presence of trans and cis 18:1 isomers was determined in samples of commercially available blended feed-grade fats (BFF) used in poultry diets. Total lipids (TL) were extracted with chloroform:methanol (2:1, v/v); triglycerides (TG) and free fatty acids (FFA) were separated by thin-layer chromatography (TLC). The trans and cis isomers of 18:1 in TL, TG, and FFA were separated by argentation TLC and quantified by gas-liquid chromatography (GLC). The trans isomers of 18:2 were directly separated by GLC. The BFF contained many trans and cis 18:1 isomers. Total trans 18:1 ranged from 0 to 11.7% in the BFF sources and up to 31.3% of the total 18:1 isomers. The trans isomers of 18:2 were found in lesser amounts (.1 to .7%). Levels of essential fatty acids linoleate and linolenate ranged from 11.5 to 50.3 and .7 to 2.8%, respectively. Ratios of saturated:unsaturated fatty acids ranged from .17 to .68. These data indicate that trans and cis isomers of 18:1 are present in varying amounts in BFF.