Exploring the Genetic basis of Residual Feed Intake (RFI) to predict feed-efficient in beef bulls

Abstract

Residual feed intake (RFI) is defined as the difference between actual feed consumption and the predicted feed intake based on a bull's live weight, growth, and maintenance needs. Bulls with low RFI values are considered more efficient because they have reduced feed costs compared to those with high RFI values. Identifying marker genes that control RFI is challenging due to the significant variation in differentially expressed genes (DEGs) and the antagonistic expression of genes that regulate the RFI trait in bulls. In this literature review, we searched for potential genes, their positional single nucleotide polymorphisms (SNPs), their chromosomal locations, and their expression patterns to better understand the regulation of RFI traits in bulls. Based on specific inclusion criteria, this review explored over 200 studies on RFI in beef bulls and steers published between 2012 and 2022. The review utilized genome-wide association studies (GWAS) and gene set enrichment analysis (GSEA) and identified 511 genes located on 240 chromosomal loci in 7,992 beef bulls. Of these genes, 52 were consistently reported as modulating RFI, while 469 were unique and only reported once. During this period, 228 of the 244 chromosomal loci were reported multiple times, while 16 were reported only once. The literature search revealed that 11 studies linked the bovine chromosome 6 (BTA6) to RFI quantitative trait loci (QTLs) in bulls. Similarly, eight studies linked BTA8, ten linked BTA7, and eight linked BTA11 to RFI QTLs. Additionally, 228 SNPs were identified across 30 chromosomal locations between 2012 and 2023. This review provides novel insights into the molecular mechanisms underlying feed efficiency (FE) regulation and lays the groundwork for identifying molecular markers associated with FE in bulls across all breeds and populations.