Glycogen and lactate contents, pH and meat quality and gene expression in muscle Longissimus dorsi from iberian pigs under different rearing conditions

Forty-four pure Iberian pigs were reared under four different rearing systems: i. Free range conditions and fed on acorns and pasture (AGFR), ii. Free range conditions with grass availability and fed on concentrate (CGFR), Intensive system and fed on concentrate supplemented with 100 ppm of alpha-tocopheryl acetate (alpha-Tac) (CI) and iv. Intensive system and fed on concentrate supplemented with 200 ppm alpha-Tac (CEI). The aim was to investigate the effect of rearing system on pH values, glycogen content [GLY] and lactate content [LAC], myofibrillar and sarcoplasmic proteins solubility and metabolic rate (R-value) in muscle Longissimus dorsi (L. dorsi) at 45 min and 24 h postmortem. In addition, at 24 h postmortem, water holding capacity (WHC), cook loss (CL), drip loss (DL) and instrumental color were analysed. mRNA expression of genes related to glycogenolysis (glycogen phosphorylase, muscle associated: PYGM) and glucose metabolism, both aerobic (pyruvate dehydrogenase kinase 4: PDK4) and anaerobic pathways (lactate dehydrogenase A: LDHA) were sampled within 45 min postmortem. AGFR muscles at 45 min postmortem had a significantly higher [GLY] than CI (P < 0.05). CEI and CGFR muscle [GLY] did not differ from CI and AGFR, with intermediate values. [LAC], pH, R-value and protein solubility, both at 45 min and 24 h postmortem, did not differ among groups. Rearing system did not affect meat quality parameters, with the exception of redness (CIE a*) that was significantly higher in muscle from AGFR pigs than in those from CEI and CGFR pigs. Meanwhile, PYGM mRNA showed overexpression in AGFR, CGFR and CEI groups compared to CI. No significant differences were found for LDHA and PDK4 genes between batches. Regarding correlations, pH had significant positive correlations with WHC and negative with CL and lightness (CIEL L*). [LAC] correlated positively with CL and CIE L * and negatively with WHC; while the pH did the opposite. The expression of the LDHA gene was negatively correlated with pH and positively with [LAC]. Positive correlations were found between PDK4 gene expression and pH and negative correlations with [LAC].