Tenderness is one of the most important meat quality traits and it can be measured through shear force with the Warner–Bratzler test. In the current study, we use the RNA-seq technique to analyze the transcriptome of Longissimus dorsi (LD) muscle in two groups of Iberian pigs (Tough and Tender) divergent for shear force breeding values. We identified 200 annotated differentially expressed genes (DEGs) and 245 newly predicted isoforms. The RNAseq expression results of 10 genes were validated with quantitative PCR (qPCR). Functional analyses showed an enrichment of DE genes in biological processes related to proteolysis (CTSC, RHOD, MYH8, ACTC1, GADD45B, CASQ2, CHRNA9 and ANKRD1), skeletal muscle tissue development (ANKRD1, DMD, FOS and MSTN), lipid metabolism (FABP3 and PPARGC1A) and collagen metabolism (COL14A1). The upstream analysis revealed a total of 11 transcription regulatory factors that could regulate the expression of some DEGs. Among them, IGF1, VGLL3 and PPARG can be highlighted since they regulate the expression of genes involved in biological pathways that could affect tenderness. The experiment revealed a set of candidate genes and regulatory factors suggestive to search polymorphisms that could be incorporated in a breeding program for improving meat tenderness.

This experiment was conducted to investigate the effects of developmental stage, breed, and diet energy source on the genome-wide expression, meat quality traits, and tissue composition of biceps femoris muscle in growing pure Iberian and Duroc pigs. The study comprised 59 Iberian (IB) and 19 Duroc (DU) animals, who started the treatment at an average live weight (LW) of 19.9 kg. The animals were kept under identical management conditions and fed two diets with different energy sources (6% high oleic sunflower oil or carbohydrates). Twenty-nine IB animals were slaughtered after seven days of treatment at an average LW of 24.1 kg, and 30 IB animals plus all the DU animals were slaughtered after 47 days at an average LW of 50.7 kg. The main factors affecting the muscle transcriptome were age, with 1832 differentially expressed genes (DEGs), and breed (1055 DEGs), while the effect of diet on the transcriptome was very small. The results indicated transcriptome changes along time in Iberian animals, being especially related to growth and tissue development, extracellular matrix (ECM) composition, and cytoskeleton organization, with DEGs affecting relevant functions and biological pathways, such as myogenesis. The breed also affected functions related to muscle development and cytoskeleton organization, as well as functions related to solute transport and lipid and carbohydrate metabolism. Taking into account the results of the two main comparisons (age and breed effects), we can postulate that the Iberian breed is more precocious than the Duroc breed, regarding myogenesis and muscle development, in the studied growing stage.

Aim of study: To evaluate two experimental diets based on olive cake supplied during the growth period as an alternative to the restricted feeding applied in the production of Iberian pigs fattened with acorn (Montanera system). Area of study: Southwest of Badajoz, Spain Material and methods: 44 Iberian pigs were divided in three diet groups: 1) control (C) group (n=15), 2) dry olive pulp (DOP) group, fed a compound feed elaborated with olive pulp (n=14), and 3) wet crude olive cake (WCOC) group, fed a compound feed and olive cake silage supplied ad libitum (n=15). Subcutaneous fat biopsies were taken and backfat thickness and longissimus thoracis et lumborum (LTL) area were measured. In addition, quality traits (intramuscular fat percentage, color, pigment content, water holding capacity and shear force) were measured in LTL. Backfat fatty acid profile and intramuscular fat were also analysed. Main results: Significant differences were observed between groups for most of the fatty acids in backfat at 95 kg but differences were of lower magnitude at 160 kg and affected only to C16:1, C18:0, C18:1, C20:0, C20:1 and ΣSFA. Otherwise, lower values for red color and myoglobin content and higher for thawing water losses were observed for DOP pigs. The WCOC did not affect the analysed quality traits. Research highlights: Experimental diets did not have an important impact on growth, carcass composition or meat quality. Therefore, WCOC dietary treatment could be an interesting alternative that could reduce the undesirable effects of feed restriction.

We investigated the ability to predict production performance in Iberian pigs in an extensive production system from measurements of feed efficiency measured intensively. The second objective of this work was to study the relationship between feed efficiency and meat quality (composition, juiciness, tenderness, color, and subcutaneous fatty acid composition) and if cooked and cured quality properties can be predicted by properties in fresh meat. Thirty Iberian sows received successively a restricted diet of concentrate (P1concentrate) and acorns (P2acorn) intensively [...] ABSTRACT We investigated the ability to predict production performance in Iberian pigs in an extensive production system from measurements of feed efficiency measured intensively. The second objective of this work was to study the relationship between feed efficiency and meat quality (composition, juiciness, tenderness, color, and subcutaneous fatty acid composition) and if cooked and cured quality properties can be predicted by properties in fresh meat. Thirty Iberian sows received successively a restricted diet of concentrate (P1concentrate) and acorns (P2acorn) intensively