Fattori non genetici e genetici associati al fenomeno della carne destrutturata nel suino pesante

The PSE-like destructured meat defect (DES) represents an issue for the pork industry. Despite its economic relevance, little information is available in the literature regarding the incidence, environmental determinants, and genetic basis of this condition, in particular in heavy pigs destined to the production of protected designation of origin (PDO) dry-cured hams. This thesis provides an evaluation of DES in hams from 1,528 Italian heavy pigs, slaughtered at a weight (mean ± SD) of 175.2 ± 18.7 kg and an age (mean ± SD) of 9.04 ± 0.13 months, analysing its phenotypic and genomic sources of variation. The defect was observed in 23.6% of the hams and the anatomical region mostly affected by DES was the topside, with lesions in the silverside and knuckle largely co-occurring with topside involvement. While seasonal variation appeared limited, sex showed a significant association with DES occurrence, with females being more prone to DES than castrated males. Transport duration was also associated with DES. Pigs affected by DES exhibited a significantly lower average daily gain (-3.7%), slaughter weight (-3.6%), carcass weight (-3.8%), ham weight (-2.0%), ham roundness score (-14.4%), backfat, ham fat thickness scores and marbling (-4.3%, -81.5%, -48.7%, respectively). Carcass lean meat content, iodine number, linoleic acid content, omega 6 fatty acids and PUFA content were significantly higher in hams affected by DES compared to the non affected ones (+1.3%, +1.2%, +4.8%, +4.8%, +4.6% respectively). Post-mortem pH measurements were identified as key phenotypic predictors, with intramuscular pH measured four days post-slaughter (pH4d) showing excellent discriminative power (AUC = 0.953). DES exhibited a good heritability (h² = 0.42), indicating that genetics plays a significant role in determining the susceptibility to DES. The animals were genotyped using a high-density single nucleotide polymorphisms (SNP) chip (GGP Porcine 50K); after quality-filtering and imputation, the number of SNP genotypes retained was 29,538 per animal. From a genetic standpoint, although traditional GWAS did not detect genome-wide significant SNPs, variance-explained analyses revealed relevant loci on SSC1, SSC6, and SSC15, which also overlapped with regions associated with pH and muscle color. The gene-network analysis supported a polygenic and multifactorial architecture, highlighting functional groups related to biological pathways highly relevant to post-mortem muscle physiology. These include processes regulating redox balance and protection from oxidative stress, lipid and fatty acid metabolism, glucose metabolism, muscle growth and fibre composition, immune and inflammatory responses, neuronal and developmental functions, and mechanisms controlling protein turnover and cellular signalling. Overall, this study enhances current knowledge on the anatomical, biochemical, and genetic determinants of DES and provides a solid basis for targeted breeding and refined phenotyping strategies to reduce defect incidence in DOP-oriented Italian pig production systems.