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Genomic regions associated with residual feed intake of divergently selected lines of Yorkshire pigs when fed a low energy, high fiber diet
Feed intake and efficiency remain key targets for improvement in the pork industry as feed is the number one source of production costs. To better understand feed efficiency, divergent selection for residual feed intake (RFI) was performed in purebred Yorkshire pigs for 10 generations at Iowa State University. Phenotypes for RFI (n=2,623) and component traits were recorded across generations and lines (High RFI and Low RFI). A corn and soybean-meal based diet that was higher in energy and lower in fiber content (HELF) was fed during selection. To explore the effect of diet on RFI, a lower energy, higher fiber (LEHF) diet was fed to a subset of pigs from generations 8, 9 and 10 (n=314). The LEHF diet had 18% less net energy and 175% more neutral detergent fiber, yet lysine to metabolizable energy ratios were similar between diets. Pigs were genotyped using the Illumina Porcine SNP60 BeadChip. Serão et al. (2016) reported genomic regions on Sus scrofachromosome (SSC) 2 and 6 associated with RFI of pigs fed the HELF diet (n=1,692). The objective of this study was to identify genomic regions associated with RFI when pigs were fed a LEHF diet. Using bivariate models for RFI between diets, heritability of RFI was estimated to be 0.24 ± 0.05 for the HELF diet and 0.35 ± 0.17 for the LEHF diet, while the genetic correlation of RFI between diets was 0.82 ± 0.28. Pigs (n=310) fed the LEHF diet with phenotypes and genotypes for 46,467 SNP, after quality control, were used for a genome wide associate study. GenSel4 was used to fit BayesB and C models with π =0.9933. Results from BayesC found no significant genomic associations for RFI. BayesB identified associations for RFI on SSC 6 and 14 that each explained ~0.75% of the genetic variance and on SSC 1, 5, and 16 that each explained ~0.50% of the genetic variance. None of these regions overlapped with those reported by Serão et al. (2016). In conclusion, RFI is a polygenic trait with many QTL across the genome with small effects and those effects may depend on the diet fed. This work was supported by AFRI-NIFA grant #2011-68004-30336.
Keywords: genomic regions, RFI, swine