Distribution of trans and cis 18:1 fatty acid isomers in chicks fed different fats

The effects of dietary trans isomers of 18:1 (t-18:1) were studied in chicks by feeding purified diets containing soybean oil (SBO) as the control lipid source, saturated fat (SF), hydrogenated soybean oil (HSBO), or spent restaurant grease (SRG) for three weeks. Argentation thin-layer chromatography and gas-liquid chromatography were used to separate trans and cis (c) isomers of 18:1 and to determine the fatty acid composition in chick tissues. Chicks fed HSBO (34% t-18:1 of total 18:1) had weight gains similar to those of chicks fed SF but significantly (P less than .05) lower gains than those of chicks fed SBO or SRG. No differences were observed in feed conversion ratios (total feed:total gain) across treatments. Trans-18:1 was incorporated into liver, heart, lung, and abdominal fat pad of chicks fed HSBO. Chicks fed HSBO had higher levels of c-16:1 omega 7 and 18:1 and lower levels of linoleate and arachidonate in tissue lipids. Similar changes were observed in liver microsomal fatty acids of chicks fed SRG that was adequate in linoleate, but which contained low levels of t-18:1 (4% of total 18:1). Positional and geometrical isomers of 18:1 appear to impair essential fatty acid metabolism in the chick.