engleski

Effect of dietary oils on lipid and protein oxidation of broilers tissues

The addition of unsaturated fatty acids to broilers feed in order to improve the fatty acid composition and quality of meat used in human nutrition may also cause increased susceptibility to oxidation processes, leading to undesirable organoleptic changes and reduced meat storage stability. The oxidative processes in meat can be quantified by measuring lipid (Tiobarbituric Reactive Substances, TBARS) and protein oxidation products (carbonyl proteins, CP). Our experiment has been performed on broilers divided in 8 groups, each represented by 5 individuals. From the 22nd to the 42nd day of growth, to the standard broilers feed plant oils were added in concentration of 5% for groups 1 – 4 and 2.5% for groups 5 – 8. Groups 5 – 8 also received 2.5% of fish oil. Plant oils applied were sunflower, soybean, rapeseed and flax oil, for 1st and 5th, 2nd and 6th, 3rd and 7th and 4th and 8th group, respectively. At 42 day of age, birds were weight, exanguinated and defeathered. Carcasses were manually eviscerated, washed and cut. Breast and leg muscles as well as liver were dissected and frozen in liquid nitrogen. After defrosting tissues were homogenized in buffer solution. For TBARS analysis postmitochondrial fraction was prepared and reacted with 2-tiobarbituric acid. Products were detected spectrophotometrically at 532 nm. The results are expressed as milligrams of lipid peroxidation products (malonaldehyde and similar aldehydes, MDA) per kg of tissue (mgMDA×kgtissue-1). Carbonyl proteins were determined from trichloracetic homogenate precipitate in reaction with 2, 4- dinitrophenylhidrazine spectrophotometrically at 375 nm and expressed as µ ; molCO×mgprot-1. Both tissue oxidation indicators (TBARS and CP) were lowest in breast and highest in leg muscle. The highest values were detected in all tissues of broilers receiving flax oil in combination with fish oil, and lowest were in tissues of broilers receiving rapeseed oil. In broilers receiving fish in addition to plant oil TBARS and CP were significantly higher than in those receiving only corresponding plant oil. We concluded that oils containing α - linolenic acid (flax and fish oil) and docosahexaenoic acid (fish oil), which are more susceptible to oxidation processes, provoke more intensive tissue oxidative damage when added to broilers feed. Rapeseed oil containing oleic and linoleic acid caused the smallest oxidative tissue damage, while oils containing linoleic acid (sunflower and soybean oil) displayed moderate oxidative damage.

broilers ; lipid peroxidation ; TBARS ; carbonyl proteins ; plant oils ; fish oil

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