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

This study aimed at analysing the impact, on beef lipids and fatty acids and on beef colour, of dietary lipid supplements provided by extruded linseeds (rich in n-3 polyunsaturated fatty acids, n-3 PUFA) alone or with extruded rapeseed (rich in n-6 and n-3 PUFA and in 18:1n-9) in association or not with dietary antioxidants in cull dairy cows in finition. Dietary linseeds increased significantly proportions of 18:3n-3 (+56% and +36% respectively), of total trans 18:1 (+66% and +105%); and of 9cis,11trans 18:2 (CLA) (+50% and +41%) in Longissimus thoracis and Semitendinosus muscles, 18:3n-3 and CLA being known to be beneficial for the human health. Antioxidant supplements (association of vitamin E with plant extracts rich in polyphenols, PERP) reinforced the stimulating effect of lipid supplements on proportions of 18:3 n-3, 18:1trans, and 9cis,11trans 18:2 in lipids of the two muscles. Dietary n-3 PUFA reduced the capacity of plasma to resist against lipoperoxidation (−11%) favouring the formation of peroxides such as conjugated dienes (× 1.75) and malonedialdehyde (MDA, ×2). Intensity of lipoperoxidation tended to increase in beef packaged under modified atmosphere rich in oxygen (O₂/CO₂: 70/30) of the linseed group (2.96 μg/g fresh tissue) when compared to that in the control group (2.19 μg/g, p = 0.1). Combined supply of vitamin E and PERP efficiently protected beef against lipoperoxidation, even in beef packaged under modified atmosphere rich in oxygen. Beef samples packaged under air from cows of the linseed group exhibited a more intense red colour than that of cows of the control group. In cows of the linseed group submitted to an emotional stress 2 hours before slaughtering, beef samples packaged under the air or the O₂-rich atmosphere had a red colour with a lower intensity that beef samples from cows of the linseed plus antioxidants group. In conclusion, feeding strategy for finishing cull cows combining lipid (from linseed rich in n-3 PUFA) and antioxidant (vitamin E + PERP) supplements improve the health value of beef fatty acids avoiding the major risks of beef lipoperoxidation and of alteration of beef colour whatever (i) the conditions of beef ageing and packaging (especially with O₂), (ii) the level of emotional stress of animals just before slaughtering.