Genotypes within Cellular Growth and Cell Cycle Processes Associated with Feed Efficiency in Sheep

The objectives of this study were to identify single nucleotide polymorphisms (SNP) associated with residual feed intake (RFI) in wool and meat breed rams, and determine functional categories of genes potentially affected by associated SNP.  Data were collected on 7 contemporary groups composed of wool breed (n = 282) and meat breed (n = 220) rams that were measured for RFI. A multi-locus mixed model was used to conduct a genome-wide association study (GWAS) using SVS7 software for combined breeds (n = 502), and wool breed and meat breed datasets separately. Fixed effects included breed, flock, birth type and contemporary group. One SNP associated with RFI achieved Bonferroni significance (P = 1.03^-06) in meat breed rams, and 51, 45, and 52 SNP reached nominal significance (P < 0.001) in combined breeds, wool breeds, and meat breeds, respectively.  Regardless of breed, chromosomes 1 and 3 contained the highest number of SNP associated with RFI; however, no SNP were shared among the three analyses. Associated SNP accounted for 1.45%, 2.22%, and 3.02% of the variance explained for RFI in combined breeds, wool breeds, and meat breeds, respectively. The majority of genes within 100 kb of associated SNP clustered into cellular growth processes for the complete dataset, and cell cycle processes for wool and meat breed rams. Overall, results indicated that despite associated SNP differing among breeds, similar chromosomal regions and functional processes can be identified for complex traits. Chromosomal regions or cellular functions may be targeted to improve RFI in sheep.