PSIV-19 Proteomic detection of potential biomarkers for residual feed intake in Texel sheep.

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Abstract Feed efficiency is a key driver of productivity and profitability in livestock production systems. Among the different feed efficiency metrics, residual feed intake (RFI) has proven to be a valuable tool, although characterized by complex biology and regulatory mechanisms involving several genes that participate in many pathways. Although the relationship between blood plasma proteomics and RFI in sheep remains relatively unexplored, the plasma proteome interacts with all tissues through circulating factors. It may revolutionize the agricultural industry since blood collection is a semi-invasive procedure. Thus, this study investigated biological processes and pathways underlying RFI in Texel sheep, as well as potential biomarkers by blood plasma proteome analysis. A 70-day long feed efficiency test was performed in 40 Texel females that belonged to the same contemporary group, aging less than one-year-old and with 32.28 ± 4.42 kg initial body weight. The feed intake of each animal was recorded daily by electronic feed bunks (Intergado Science, Ponta®, Brazil), with ad libitum access to diet and water. Animals were subjected to 14 days of adaptation to the diet before the feed efficiency test. RFI was calculated at the end of the feed efficiency test as the difference between observed and expected dry matter intake based on a linear regression of mid-test metabolic body weight and average daily gain for the trial. After the feed efficiency test, blood samples were collected from the jugular vein of each animal, and the plasma samples of a subset of 12 extreme animals were used for proteome analysis by liquid chromatography-tandem mass spectrometry: highest RFI (n=6) and lowest RFI (n=6). The data were processed using the Comet algorithm and the ovine Uniprot database. Data validation and scoring were performed using the Peptide Prophet and Protein Prophet algorithms (FDR ≤ 0.05). The intensities for each peptide were acquired and quantified using the XPRESS algorithm, and the intensities of individual peptides were aggregated to provide a total protein intensity. Proteins with fold-change ratios ≥ 2 and ≤ 0.5 were considered as differentially abundant (P ≤ 0.05). A total of 24 differentially abundant proteins were identified between the two experimental groups. Furthermore, functional enrichment analysis revealed several biological processes and pathways that contributes to RFI, such as immune and inflammatory responses (KNG1), carbohydrate binding (OS9), protein digestion and absorption (COL28A1), mineral absorption (LOC101117129), fatty acid binding (AFM), metabolism of cholesterol (CAT), and vitamin transport (AFM). This study sheds light on differentially abundant proteins influencing RFI in Texel sheep, contributing to our understanding of the mechanisms underlying feed efficiency in sheep. In addition, these findings provide valuable insights into potential biomarkers for RFI, which provide helpful sources in developing novel selection strategies for breeding programs.

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