Innovative tools for phenotypic characterization and genetic improvement of meat quality in the Piemontese breed.

The main objective of this thesis was to perform a comprehensive investigation of the possibilities for the improvement of meat quality traits focusing on the development of innovative tools. The study was carried out sampling 1,327 Piemontese young bulls. Animals were fattened in 115 farms and slaughtered at the same commercial abattoir. Information about farms fattening system was collected through on field surveys. After slaughter, the following carcass traits were recorded: carcass weight, carcass conformation, age at slaughter and carcass daily gain. Individual samples of the Longissimus thoracis muscle were collected and transferred to the laboratory for meat quality analyses: muscle pH, colour parameters of lightness (L*), redness (a*), yellowness (b*), hue angle (h*), chroma (C*), purge losses, cooking losses, and Warner Bratzler shear force, all measured at 7 d after slaughter. On each meat sample, 5 spectra were collected in a reflectance mode at the abattoir with a portable top-ranking visible near-infrared spectrometer and an hand-held spectrometer. Calibration equations were developed after conventional meat quality assessment using Bayesian methods. The ability of spectroscopy in predicting meat quality traits was evaluated comparing the performances of the two spectrometers. Genetic correlations between carcass and measured meat quality traits were investigated, as well as genetic relations of meat quality traits with predictions obtained by spectral data. All the sampled young bulls were genotyped with the “GeneSeek Genomic Profiler Bovine LD” (GGP Bovine LD) array containing 30,111 SNPs. A combination of Genome-Wide Association and Pathway Analysis was performed to identify the genomic regions and biological pathways contributing to the variability of carcass and meat quality traits. Genomic variance components and SNP effects were estimated with bayesian methodology and a SNP-BLUP model. Genomic heritability and direct genomic breeding values were computed, assessing the possibility of implement genomic selection for meat quality traits. Six main typologies of fattening system were identified within the Piemontese breed. Carcass traits were deeply affected by production system, while little effects on meat quality, limited to colour traits, were observed. The small effect of beef production system showed that the variability of meat quality traits mainly depends on individual animal factors, shifting the possibilities for their improvement to genetic aspects. All the meat quality traits showed not negligible heritabilities, allowing their improvement through selection. They also displayed genetic relationships with carcass traits, indicating a possible modification as a correlated response to selection for growth rate and muscularity, traits currently included in the breeding goal of the Piemontese breed. However, the establishment of a direct selection procedure relies on the availability of phenotypes collected within a routine recording scheme. Predictions of colour traits and purge losses were satisfactory, whereas pH, cooking losses and shear force predictabilities were rather poor. However, all the predicted traits except shear force showed moderate heritabilities and were highly correlated with measured traits, allowing their use for selection purposes. From genetic architecture point of view of carcass and meat quality traits, our investigation highlighted that, besides myostatin, other genes contribute to explain the variability in carcass and growth characteristics. Moreover, association of pathways related to transporter activity (oxygen, calcium, ion and cation) was found with meat color parameters. Genomic heritabilities were higher than pedigree-based heritabilies for purge losses and all colour traits, while they were similar for the other meta quality traits. The accuracy of prediction of genomic breeding values was satisfactory and allows to consider genomic selection as a valid tool to improve meat quality traits in Piemontese breed.