Influence des acides gras polyinsaturés n-3 et des antioxydants alimentaires sur les acides gras de la viande et la lipoperoxydation chez le bovin en finition

The aim of this study was to analyze, on beef lipids and FA and on beef colour, the impact ofextruded linseed (rich in n-3 PUFA) given alone or with rapeseed (rich in n-3 and n-6 PUFA and in 18:1n-9) in association or not with antioxidants given to Normand (fat breed) cull cows during the finishingperiod. Dietary linseeds significantly increased proportions of 18:3 n-3 (+56 and +36% respectively),total trans 18:1 (+66 and +105%); and of 9cis, 11trans 18:2 (CLA) (+50 and +41%) in LT muscle ofwhich 18:3 n-3 and CLA are known to be beneficial for the human health. Addition of antioxidants(vitamin E plus plant extracts rich in polyphenols, PERP) reinforced the stimulating effect of lipid supplementson proportions of the three considered FA (18:3 n-3, total trans 18:1, 9cis, 11trans 18:2) intotal lipids of both muscles. Dietary n-3 PUFA reduced the resistance capacity of plasma against lipoperoxidation(–11%) favouring peroxidized products formations such as conjugated dienes (×1.75) andmalonedialdehyde (MDA, ×2). Intensity of beef lipoperoxidation (estimated by MDA level) tended tobe higher in meats packaged under modified atmosphere rich in oxygen (70%) in the linseed group(2.96 μg/g of tissue) compared to that of the control group (2.19 μg/g of tissue, P = 0.1). Dietary vitaminE provided with PERP effectively protected beef against lipoperoxidation, even in beef packagingswith O2. Beef under air packaging from cows given the linseed supplement had a higher redness valuethan that from control cows. In the case of animals given lipid supplemented diets and submitted to anemotional stress, beef packaged under air or modified atmosphere rich in O2 had a lower redness thanthat of the same animals given lipids associated to antioxidant supplements. We concluded that thedietary strategy combining addition of n-3 PUFA and of the antioxidant mixture in diets would avoidmajor risks of lipoperoxidation and alteration of colour in beef products whatever: 1) the conditions ofmeat ageing and packaging (especially those with contact with oxygen); 2) the degree of emotionalstress of animals just prior slaughter.