Ex-Foods Diets Affect the Fatty Acid Profile of the Abdominal Adipose Tissue Without Significantly Affecting the Plasma Metabolome of Postweaning Piglets

Food leftovers can be used as alternative feed ingredients for monogastric to replace human-competing feedstuffs, such as cereals, recycle a waste product, reduce the feed-food competition and keep nutrients and energy in the feed-food chain. Among food leftovers, former food products (FFPs) are no more intended for human but still suitable for animal consumption. However, the metabolic impact of FFP has never been investigated. In this study, we evaluated the impact of replacing 30% of conventional cereals with FFP on abdominal fat quality and plasma metabolome modulation in postweaning piglets. Thirty-six Large White × Landrace postweaning piglets (28 days old) were randomly assigned to three dietary groups for 42 days: control (CTR), 30% replacement of CTR with salty FFP (SA), 30% replacement of CTR with sugary FFP (SU). Body weight and feed intake were measured to calculate average daily gain, average daily feed intake and feed conversion ratio. The fatty acid profile of the diets and the abdominal adipose tissue was determined and a mass spectrometry-based untargeted metabolomics investigation was performed on plasma samples. The growth performance was not significantly affected by SA and SU diets. Despite the different fatty acid profile of the diets, the fatty acid profile of the adipose tissue was rebalanced in piglets. The plasma metabolome was more affected by the time factor rather than the treatment factor. Six metabolites were significantly altered in SA and SU groups compared to CTR: caffeine, theobromine, proline-betaine, dipalmitoyl-phosphatidylcholine (PC 32:0), spermidine and l-tryptophan. Caffeine and glycerophospholipid pathways were significantly different between CTR and SA and SU groups, although no impact on other metabolic pathways was observed. Overall, the limited impact of FFP on the abdominal fat, plasma metabolome and related pathways in postweaning piglets demonstrated the value of FFP as innovative and sustainable feed ingredients to replace human-competing feedstuffs.