Dalvit, Chiara (2008) Genetic traceability: a tool for the authentication and valorisation of animal products. [Ph.D. thesis]
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Traceability, obtained by molecular analysis, is a reliable proposal for the authentication and valorisation of animal products.
Aim of this thesis was to verify the possibility to use molecular methodologies for the assessment of a genetic traceability system able to discriminate among individuals and breeds in bovine animal products. Among the molecular markers available today, microsatellites were considered the best suiting this scope. They are widely employed due to their easy use and to their elevated polymorphism that provides a high degree of information.
The first contribution, proposes a synthesis of the major advances in individual, breed, and species genetic identification in the recent years, comparing different molecular markers and statistical approaches.
The second experimental contribution, concerns the possibility to use a set of twelve microsatellites for the individual identification of animals belonging to six bovine breeds widely reared in Italy: Holstein Friesian, Brown Swiss, Chianina, Marchigiana, Romagnola and Piemontese. The probability to find, by chance, two animals sharing the same genetic profile at the analyzed loci, was estimated considering a decreasing number of markers. The study evidenced that, investigating only the five most polymorphic markers per breed, the probability to find two identical individuals was approximately five in one million. Moreover, to reduce the laboratory work and costs, a set composed by eight markers, giving satisfactory results in all considered breeds, was assessed. Use of this technology could be useful as verification and guarantee of the information compulsorily present on the product label, to safeguard the production chain and detect possible frauds; moreover, when a more powerful and secure identification is required, for example, in the recall of all animal cuts in case of health's risks.
The third experimental contribution, deals with the investigation of twenty-one microsatellites to define a breed traceability system in four Italian beef cattle breeds: Chianina, Marchigiana, Romagnola and Piemontese. Such discrimination technique could be an important tool for product verification and valorisation. In fact, due to the high quality of their beef, these animals show a higher market price. Moreover, beef from Chianina, Marchigiana and Romagnola, is protected by the European label PGI (Protected Geographic Indication) because of its peculiarities and the limited area in which the animals are reared. Two statistical approaches were tested, the one based on a Bayesian algorithm gave best results. In fact, it achieved a correct assignment rate of 90% of tested individuals using six microsatellites. However, considering a threshold probability of 90% and using the information derived from twenty-one microsatellites, only 52 % of the genotypes were correctly allocated. Such results were mainly due to the low genetic differentiation estimated among breeds (FST = 0.049). Results suggest that, to improve the discrimination power of markers, microsatellites showing private alleles should be sought.
The last experimental contribution, aims to characterize genetically the Burlina cattle breed. Burlina is an indigenous Italian cattle breed from the Veneto region (North-East Italy); it is a small sized animal mainly reared in the mountain area of Treviso and Vicenza provinces where it was appreciated for its good grazing characteristics. Burlina has been gradually substituted by more productive breeds such as Holstein Friesian and Brown Swiss and it was seriously endangered before the beginning of a conservation plan. Nowadays about 350 animals are registered in the Italian Herd Book . In this study Burlina was genetically characterize investigating twelve microsatellites and it was compared with Holstein Friesian and Brown Swiss. The obtained results evidenced the genetic diversity and distinctiveness of Burlina population, even if the estimation of genetic distances showed a moderate/high similarity with Holstein. Moreover, the assignment of a moderate percentage of Burlina animals to Holstein Friesian, witnessed that crosses between them took place in the past. Compared to the other breeds, Burlina showed a higher genetic variability and a lower inbreeding. These results contribute to the assessment of a conservation plan aiming to conserve animals where the contribution from foreign breeds is as small as possible. The implementation of a genetic traceability system for products derived from Burlina breed (such as the typical Morlacco cheese) is of certain interest; anyway results obtained from the genotyping of the twelve microsatellites are not sufficient to achieve this goal
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