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|Authors: ||Mattioli, Simona|
|Internal Tutor: ||TEROVA, GENCIANA|
|Co-tutor: ||CASTELLINI, CESARE|
|Title: ||Preservation and diffusion of some native Italian chicken breeds.|
|Abstract: ||The safeguard of animal biodiversity is a strong objective in developed countries. The genetic variability gives the chance to select individuals more adapted to climatic changes, diseases and potential market variations. Because of the different environments, up to decades ago, Italy showed a considerable biodiversity in native livestock breeds and populations. Within the last one hundred years, the number of endangered native breeds dramatically increased, leading to an irreversible loss of genetic resources. About 60% of chicken breeds reared in Italy until some decades ago are currently disappeared. The reason of this trend is mainly due to the selection of specialized breeds very efficient in converting feed into egg and meat. Contemporarily, the abandoning of rural breeding in favour of intensive farming system which uses few selected chicken lines exacerbates such negative trend. The extant breeds, excluded from commercial selection process, represent an important source of variability. The main critical point of local breeds is generally the low productivity which implies that a large part of body resources are used for maintenance (kinetic activity, immune response) and only the residual are assigned to production traits. This fact implies a low productivity but in the same time renders the animal adaptable to poor environment. In particular seems that such pure breed had more aptitude to elongate and desaturate essential fatty acids (linoleic acid, n-6 and α-linolenic acid, n-3) in their long chain derivates (arachidonic acid-AA, eicosapentaenoic acid-EPA, docosahexaenoic acidDHA), with a consequently greater accumulation on products. This would represent an important goal for the livestock word, since it provides a compromise: between rusticity and economic sustainability and designs a healthier chicken meat for nutritional-conscious consumers, also in accordance with a big problem of the safeguard of the biodiversity.
The aim of the present PhD work was to study the adaptation response of local chicken breed to extensive farming conditions. The experimental activity is divided into different experiments where we analyzed the behavior and welfare of different poultry breeds in extensive farming system and the quality of the products (meat and eggs) with a focus on lipid content and the metabolism of Long Chain Polyunsaturated Fatty Acids (LC-PUFA). It was also studied the metabolic pathways of LC-PUFA and how different genotypes respond to feed changes testing the hypothesis that nutrition can influence the ontogenetic development.
In detail the effect of extensive farming systems which implies large availability of pasture on different chicken genotypes (local breeds vs commercial hybrids) was compared. The main traits that have been evaluated are: productive performance, health and welfare, immune response and qualitative characteristics of product. Different physiological (IMMUNITY: lysozyme, complement, serum bactericidal activity; OXIDATIVE STATUS: ROS, antioxidant power), and ethological indicators (behavior, tonic immobility, body lesions) have been used for this purpose. Nutritional characteristics of eggs and meat, with particular attention to oxidative and fatty acid profile were studied through the evaluation of TBARS, tocopherols, carotenoids, polyphenols, PUFA n-3 and n-6 content. Great emphasis has been paid to the study of LC-PUFA since local strain seemed more efficient in the synthesis of these fatty acids.
In particular in the experiment 1 the adaptive response of Ancona laying hens to extensive farming system in comparison to commercial hybrids has been analyzed. Ancona birds showed a specific ethological profile associated with very good welfare conditions, better immune system and oxidative status. The Ancona breed seems more adapted to less controlled environment and showed a higher percentage of "natural” behavior. Such behaviors are high in energy cost, allowing the more selected birds to save energy which could be reallocated to production traits. At the same time, the lower productivity of Ancona birds resulted in a better balance with the extensive environment, as evidenced by health status and mortality rate.
In the experiment 2 the meat traits of six hundred male chicks from slow-growing (Leghorn, Ancona, Cornish x Leghorn), medium-growing (Naked Neck, Kabir) and fast-growing (Ross) strains have been studied. The physiological state of the birds appears to be inversely correlated with the genetic selection, indeed the slow-growing showed more marked natural behaviors, followed by the medium-growing. They showed a good adaptation to extensive environment. Indeed the slow-growth rate is only a prerequisite for adaptability to the extensive system; other traits as the grazing attitude, kinetic activity, body structure and the immune response greatly affect such adaptation. It has been reported that the most relevant role of grass in organic poultry is represented by the intake of several bioactive compounds (i.e. PUFA, vitamins and pigments) with a direct effect on the quality of meat and eggs. For these reasons, it is important to determine the intake and the nutritional relevance of pasture to develop suitable free-range diets and to investigate the transfer of the above-mentioned compounds into the poultry products. In the experiment 3 eggs quality was been assessed. Ancona hens produced a lower number of eggs than commercial line but markedly different from the qualitative point of view. Indeed, Ancona eggs compared to Hy-line had higher carotenoid, polyphenol and tocopherol contents that in turn have a relevant effect on human health. Even the fatty acid profile improved (lower n-6/n-3 ratio; higher C18:3n-3 and LC-PUFA n-3); this latter fact confirms the ability of the hen to elongate/desaturate linolenic acid and to transfer n-3 LC-PUFA to the egg where exert important role during the chick growth. These differences were mainly due to the availability of green pasture and to the higher pasture attitude of Ancona hens. In experiment 4 we analyzed the fatty acid and antioxidant profile of breast meat from chickens reared according to the organic system. The slow-growing strains are egg-type lines which seem to have a higher efficiency in LC-PUFA deposition respecting to meat-type, being that elongation is partly affected by the estrogen level. Concerning the content of saturated fatty acids (SFA), the highest value was observed in fast-growing genotype. However, the meat of slow-growing chickens had lower lipid stability despite higher antioxidant content probably due to the kinetic behavior and the resulting pro-oxidative metabolism. The results of this study indicate that in extensive farming chicken genotypes play an important role in the fatty acid composition of meat. This finding assumes great importance because health concerns over human fat intake are one of the main factors contributing to the decline of meat intake. The observed differences among poultry genotypes indicate that a suitable compromise between rusticity and economic sustainability could be found and a healthier chicken meat for nutrition-conscious consumers could be designed. With the aim to improve the nutritional value of products a relationship between genotype and desaturating ability was evidenced with a significant impact on the PUFA content in the meat. In the experiment 5 we have estimated the lipid indices of six chicken genotype organically reared. We can said that the differences in meat lipid content are affected by breed, and that the pure breed had a two time higher Δ5/Δ6-desaturase index value than medium and fast-growing strains. To confirm our previously estimated, we have evaluated the direct measure of different enzymatic activity and gene expression of the above-mentioned complex in liver mitochondria in the experiment 6. Three groups of laying hens for each genotype (slow-, fast- and slow x fast-growing crossing) were fed with a standard diet. To hatch, 5 chicks/genotype were sacrificed and the liver was taken for enzyme activity and gene expression of Δ6-desaturase. Slow-growing chicken in comparison to fast-growing strain showed a higher desaturase activity. Data showed that the mRNA expression of FADS2 gene is strongly correlated with genetic selection. It seems to be higher in mediumgrowing strains although their enzyme activity was intermediate. Finally, in the experiment 7 we have tested where possible to modified lipid metabolic pathway with dietary supplementation of precursor (linolenic acid) or directly LC-PUFA (EPA and DHA). Three groups of laying hens for each genotype (slow-growing vs fast-growing) were fed with three different diets: control (standard diet), LCPn-3 (standard diet with 3% fish oil) and LNA (standard diet with 10% of linseed). Enzyme activity and gene expression of Δ6-desaturase were assessed to chicks liver as previously mentioned. The results showed that diets slightly affected lipid metabolism whereas the genetic effect was confirmed. Data reported in these last experiments showed that the expression and activity of Δ6-desaturase is strongly correlated with the genotype, so reaching an important objective for the food industry, since dietary modifications do not seem able to change the lipid metabolism. Concluding, my PhD work has the aim to assess the use of Italian local strains in extensive farming system, not just to safeguard the breeds from extinction, but also to exploit them economically, given the higher adaptability to poorer environment and the particular PUFA metabolism. They could represent an important source of gene bank, indeed selection processes and crosses of such strain with other more productive strains, could be a good alternative. In particularly, these genotypes could be exploited as suitable strains for the production of meat and eggs having higher nutritional value.|
|Keywords: ||Avian biodiversity, native breeds, extensive rearing, lipid metabolism, meat, eggs.|
|Subject MIUR : ||AGR/20 ZOOCOLTURE|
|Issue Date: ||2014|
|Doctoral course: ||Analisi, Protezione e Gestione delle Biodiversità|
|Academic cycle: ||27|
|Publisher: ||Università degli Studi dell'Insubria|
|Citation: ||Mattioli, S.Preservation and diffusion of some native Italian chicken breeds. (Doctoral Thesis, Università degli Studi dell'Insubria, 2014).|
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