For increasing energy value of feed mixtures, we are adding fat, especially vegetable oils. These oils are rich in polyunsaturated fatty acids, which are the most susceptible to oxidation, thus they worsen the oxidative stability of feed mixtures. In this research, we studied effect of natural antioxidants, olive leaf extract and marigold extract, and synthetic antioxidant on oxidative stability of feed for broiler chicken, supplemented with linseed or walnut oil. In our experiment, which we carried out in two parts, we used 8 different feeds, 4 with added linseed oil and with or without antioxidants, and 4 with added walnut oil and with or without antioxidants. We measured lipid peroxide content (LP), thiobarbituric acid reactive substances, malondialdehyde (MDA), fatty acid composition and vitamin E. The results show, that olive leaf extract did not slow oxidation process, in both, LP and MDA measurements, it even speed it up (pro-oxidative effect). Marigold extract and synthetic antioxidant had similar results, but we cannot claim that they successfully inhibited lipid oxidation, because the scale of oxidation was similar to the feed without added antioxidant. The analysis of FA and vitamin E during storage of feeds show a decrease of polyunsaturated fatty acids and vitamin E, which negatively effects nutritional value of feed.
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