Occurrence of dietary unsaturated fatty acids and their biohydrogenation products in muscles of non-ruminating foregut fermenters
Muscles of ruminants contain higher proportions of saturated fatty acids (SFA) and monounsatured FA, but lower proportions of polyunsaturated FA (PUFA), than those of monogastric herbivores, which is considered unfavourable for human health. This is explained by an almost complete microbial biohydrogenation (saturation) of dietary PUFA in the rumen prior to reaching the site of FA absorption – the small intestine. The objective was to investigate whether the muscles of non-ruminating foregut fermenter contain more PUFA and more biohydrogenation products than those of ruminants, due to their shorter passage times and thus incomplete biohydrogenation of C18 PUFA in the forestomach. The studied intermediates formed during biohydrogenation were cis-9, trans-11 C18:2 conjugated linoleic acid (CLA) and trans-11 C18:1 vaccenic acid (TVA). The study species included Bennett wallabies (Macropus rufogriseus, n=12) and collared peccaries (Pecari tajacu, n=10). Wallabies were free-ranging on grass pastures. Peccaries were maintained on a zoo diet (75% apples, carrots; 25% hay, bread). Biceps femoris muscles were sampled from carcasses. Fatty acid methyl esters were separated on a SupelcowaxTM-10 column and the isomers of C18:1 on a Varian column after split injection in a HP 6890 gas chromatograph. The ratio of SFA:PUFA in muscles of wallaby and peccary was with 0.6 and 1.6, respectively, lower than in domestic ruminants (>4) and in domestic pigs (2.6). In wallaby muscles, the concentration of TVA plus CLA was with 8% of total fatty acids (tFA) higher than in ruminants (2.6% tFA), with a TVA:CLA ratio of 3.7 (ruminants: 2.1). In peccary muscles, CLA and TVA were not detectable (<0.1% tFA) which therefore resembled the domestic pig. In conclusion, the results indicate that muscles of non-ruminating foregut fermenters are less saturated than those of ruminants and pigs. However, occurrence of trans fatty acids was not uniform for the studied non-ruminating foregut fermenters, which may be related to differences in diet, microbial population and endogenous desaturation.
trans fatty acids, wallaby, peccary