Candidate blood biomarkers linked with feed intake efficiency and weight gain in sheep

Feed consumption and weight gain critically influence sheep production profitability. Therefore, selecting animals that maintain growth while reducing feed intake is desirable. However, measuring residual intake gain (RIG) is resource-intensive, requiring extended monitoring of both feed intake and weight gain. Candidate blood metabolites linked to RIG may provide a practical tool for early selection. We assessed feed efficiency (FE) in 62 Rideau Arcott ewe lambs over 64 days, categorizing animals into efficient and inefficient groups using RIG. Serum metabolites were analyzed via direct injection liquid chromatography tandem mass spectrometry with a reverse-phase DI/LC–MS/MS custom assay, and associations with FE classifications were explored using multivariate and univariate statistical analyses. Candidate metabolites differentiating efficiency groups included citric acid, PC aa C32:2, and SM(OH) C22:1 (AUC = 0.82) at day 0, LysoPC a C18:1, SM C20:2, C7DC at day 28 (AUC = 0.84) and SM C16:1.1, PC ae C40:6.1 at day 64 (AUC = 0.77). Pathway analysis highlighted glycerophospholipid and arachidonic acid metabolism as consistently enriched across timepoints. Temporal kinetics analysis identified SM C20:2, LysoPC a C18:1, and butyric acid (p < 0.05) as varying between groups over the feeding period. Seven previously unreported metabolites in the Livestock Metabolome Database were detected in sheep serum. This exploratory study identifies metabolites and pathways associated with divergent RIG phenotypes in ewe lambs and suggests that blood metabolomics could complement performance records in FE improvement programs.