The trans -10 shifted ruminal biohydrogenation (BH) of unsaturated fatty acids (FA) pathways is characterised by the replacement of trans -11 18:1 by trans -10 18:1 as the predominant ruminal BH intermediate. The t 10-shift occurs frequently in animals kept in intensive feeding systems and affects the nutritional quality of ruminant-derived foods. This study aimed to phenotype the prevalence and variability of the t 10-shift in a large population of finishing lambs and to relate it to rumen fermentation parameters, microbial lipid markers, and adipose tissue FA. A total of 630 lambs from seven genetic groups were finished in a lamb finishing unit on a high-concentrate diet. The sampling covered 11 collection occasions at the slaughterhouse between 2022 and 2024. Rumen digesta, collected post-mortem, were analysed for volatile fatty acids (VFA), long-chain FA, and dimethyl acetals (DMA), while kidney knob channel fat (KKCF) was analysed in a subset of animals (n = 111). The t 10-shift ratio ( t 10-18:1/ t 11-18:1) in the rumen content was >1 for 89% of the animals. Significant genetic group effects were observed for rumen pH, VFA, DMA, and FA composition, including C18 intermediates. Trans -10 18:1 and t 10-shift ratio were negatively correlated with rumen pH and 18:0, indicating more incomplete ruminal BH pathways under acidic conditions. In KKCF, differences in trans -18:1 isomers were detected among groups, and rumen t 10-18:1 and t 11-18:1 were positively associated with the deposition of t 10-18:1 and t 11-18:1+ c 9 t 11-18:2 in adipose tissue, respectively. Notably, a minority of animals appeared resistant to the t 10-shift despite standardised finishing conditions, highlighting potential for genetic selection.
Manuel et al. (Wed,) studied this question.
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