Differences in Muscle Lipogenic Gene Expression, Carcass Traits and Fat Deposition among Three Iberian Pig Strains Finished in Two Different Feeding Systems

SIMPLE SUMMARY: The Iberian pig is known for the high quality of its products, mostly due to the unique lipid profile of its meat. There are several studies comparing commercial breeds or crosses with the Iberian pig, but there are only a few that compare different strains within the Iberian breed. The aim of this study was to compare carcass traits, fat deposition and gene expression in muscle, of genes involved in lipogenic metabolism in three different strains of Iberian pig finished in two feeding systems. Torbiscal was the strain with the largest lean body development and, therefore, had the highest prime cuts (ham, foreleg, and L. thoracis) traits; Retinto strain showed the highest intramuscular fat and MUFA content; while Lampiño was the strain with the highest SFA, PUFA and lipogenic ratios. On the other hand, animals following a concentrate-based diet had greater ham (posterior limb, mainly composed of semintendinosus, gluteus and biceps femoris muscles), Longissimus thoracis, prime cuts yields and SFA percentage, than animals following an acorn-based diet. In relation to the gene expression, Retinto and animals following a concentrate-based diet showed the highest expression of several genes related to lipid metabolism. These results evidence the differences between the Iberian strains and the effects of the production system in terms of morphology and lipid metabolism. ABSTRACT: The Iberian pig breed includes several well-differentiated strains. The present study evaluated carcass traits, fat deposition and muscle expression of important lipogenic genes (SCD, ME1, ACACA, FASN, EGR1, ACOX and ACLY) using 65 male pigs of 3 Iberian strains (20 Lampiño, 23 Torbiscal, and 22 Retinto) finished either in a conventional, concentrate-based system (CF) or in montanera (MF), a traditional free-range system with acorn feeding. Torbiscal had the highest ham, Longissimus thoracis and prime cuts yields, and the thinnest subcutaneous adipose tissue (SAT). Retinto had the highest monounsaturated fatty acids (MUFA) and percentage of intramuscular fat (IMF), while Lampiño had the greatest content of saturated fatty acids (SFA), polyunsaturated fatty acids (PUFA), atherogenic (AI) and thrombogenic (TI) indexes in SAT. Conventionally finished pigs had the highest ham, L. thoracis and prime cuts yields, and SFA. Montanera-finished animals had the highest PUFA and MUFA contents, and the lowest AI, TI and n6/n3 ratio in SAT. In relation to gene expression, Retinto had the greatest SCD, FASN and ACLY levels. Most studied genes were overexpressed in CF pigs. In conclusion, MF pigs had healthier fat than CF pigs, and Retinto had the healthiest fat and the greatest lipogenic trend in muscle, supported by IMF and lipogenic gene expression.