We examined the amount of marbling and tested the genome of boars from 5 breeds of Duroc, Iberian, Lacombe, Berkshire and Pietrian that were commercially available for a swine herd in Canada. The marbling was ranked according to the amount of intramuscular fat % obtained in loin chops consisting of the longissimus dorsi muscle. The genetics were analysed by genome wide association study using 80,000 single nuclear polymorphism (SNP) microarrays. Our samples had pork that achieved > 7 % IMF from 110kg animals. Meta-analysis revealed SNP markers that were associated with the highest marbled pork chops on chromosomes 5, 7, and 16. Using the susScr 11.1 map, we determined that the nearest genes were SSNP, Rh glycoprotein and EGFLAM. We tested a sub-population of Duroc sired animals and found a different set of markers close to GRLB and KCNJ3 on chromosomes 8 and 15. Based on our sample, we can achieve pork with good marbling from animals conventionally raised to standard market weights of 110kg. The choice of a good marbling line of pig is not necessarily breed specific.

The aim of this study was to identify differentially expressed genes, biological processes and metabolic pathways related to adipogenesis and lipogenesis in calves receiving different diets during the cow-calf phase. Forty-eight uncastrated F1 Angus × Nellore males were randomly assigned to two treatments from 30 days of age to weaning: no creep feeding (G1) or creep feeding (G2). After weaning, the animals were feedlot finished for 180 days and fed a single diet containing 12.6% forage and 87.4% corn-based concentrate. Longissimus thoracis muscle samples were collected by biopsy at weaning for transcriptome analysis by RNA-Seq and at slaughter for the measurement of intramuscular fat content (IMF) and marbling score (MS). Animals of G2 had 17.2% and 14.0% higher IMF and MS, respectively (P < 0.05). We identified 947 differentially expressed genes (log2 fold change 0.5; FDR 5%); of these, 504 were up-regulated and 443 were down-regulated in G2. Part of the genes up-regulated in G2 were related to PPAR signaling (PPARA, SLC27A1, FABP3, and DBI), unsaturated fatty acid synthesis (FADS1, FADS2, SCD, and SCD5), and fatty acid metabolism (FASN, FADS1, FADS2, SCD, and SCD5). Regarding biological processes, the genes up-regulated in G2 were related to cholesterol biosynthesis (EBP, CYP51A1, DHCR24, and LSS), unsaturated fatty acid biosynthesis (FADS2, SCD, SCD5, and FADS1), and insulin sensitivity (INSIG1 and LPIN2). Cow-calf supplementation positively affected energy metabolism and lipid biosynthesis, and thus favored the deposition of marbling fat during the postweaning period. Here it was shown, in an unprecedented way, by analyzing the transcriptome, genes, pathways and enriched processes due to the use of creep feeding.