SELENIUM AND OTHERS TRACE MINERALS IN DAIRY SHEEP CHAIN IN SARDINIA

Minerals solve important roles in livestock because are part of metabolic processes, such as growth development, immune system and reproductive outcome. Among minerals, Selenium (Se) is part of in several important metabolic pathways, it is the constituent of different groups of molecules and selenoproteins. Sheep appear to be resistant to Se poisoning, it is taken by the diet. The recommended Selenium intake is around 100 μg kg-1 of DM, while levels of toxicity are found in diets with quantities of selenium higher than levels of 500 μg kg-1of DM. Selenium deficiency or toxicity are nutrition and environmental problems related to sheep livestock in Sardinia. The objective of this thesis was to characterize and measure the content of selenium and some essential minerals and some toxics element in soils, pastures, blood and milk of sheep in different farms of north Sardinia. For these reason in this survey were studied the essential and toxic minerals content and the fatty acid profile of colostrum in Sarda dairy sheep; The seasonal evolution of essential and Toxic minerals in milk and blood and their relationships and the minerals content in meat and organs of lambs. In conclusion, this survey made it possible to explore further the seasonal variation of minerals in milk, colostrum quality and blood relationships with them, and how they can influence the life of lactating ewes without effects on production traits.

Selenium (Se) is part of several important metabolic pathways, it is the constituent of several groups of molecules and selenoproteins. The recommended intake of Se in the sheep diet is about 100 μg kg-1 of DM, while levels of toxicity are found in diets with quantities of Se higher than 500 μg kg-1 of DM; level of deficiency are found in diets with quantities of less than 20 μg kg-1 of DM. Se deficiency is associated with White Muscular Disease (WMD), a nutritional myopathy. Selenium is essential for sheep and lambs because it must be supplemented by the diet, together with other minerals, both essential and toxic and other elements, they give us an overview of the management of the farm and the surrounding environment. In general minerals play an important role in sheep livestock because they are part of metabolic processes, such as growth development, immune system and reproductive outcome. Selenium deficiency or toxicity and other mineral levels are nutritional problems associated with sheep livestock in Sardinia. For these reasons fats, proteins and seven essential and toxic minerals (copper (Cu), manganese (Mn), zinc (Zn), nickel (Ni), lead (Pb) and cadmium (Cd) were detected in all samples of colostrum, milk, blood, soil and feed. The main objective of this thesis was to characterize and measure the content of essential minerals, with particular reference to Selenium, and of some toxic elements in soils, pastures, blood and colostrum of milk and sheep in different farms of the north Sardinia. This investigation has allowed us to characterize for the first time the composition of Sardinian sheep colostrum in terms of mineral elements, acid profile and immunoglobulins, the strong correlation between Ntotal and Immunoglobulins. It allowed us to monitor changes in blood and milk minerals during breastfeeding. The low mineral correlations between blood and milk highlight the better understanding of the mechanisms of mineral transfer in the mammary gland. These trace elements can be another important indicator of the nutritional quality and wholesomeness of the tin, but could also be used as an environmental quality indicator