Z. 2003. Dietary manipulation to increase conjugated linoleic acids and other desirable fatty acids in beef: A review. Can. J. Anim. Sci. 83: 673-685. The diet is the source of many essential fatty acids such as linoleic and linolenic acids for all mammals. These fatty acids either, as altered isomers or as other elongated products, have been found to provide unique advantages to human health. Currently two conjugated linoleic acids (CLA) isomers (cis-9, trans-11 C18:2; trans-10, cis-12 C18:2) and two elongated products of linolenic acid [eicosapentaenoic acid (EPA, C20:5 n-3), docosahexaenoic acid (DHA, C22:6 n-3)] have been recognized for their roles in maintaining human health. Consumers can obtain these functional fatty acids from beef if the feeding management of beef cattle can be altered to include precursor fatty acids. Diet, breed, and gender are important factors that affect total fat content and/ or the fatty acid profile of beef with regard to CLA, EPA, and DHA. Diet provides the precursor fatty acids that are altered and deposited, and breed dictates, the amount of fat that is deposited. These fatty acids can be increased in beef by increasing the forage:concentrate ratio, inclusion of non-fermented forage, and supplementation with various oils or oil seeds. The CLA and vaccenic acid (trans-11 C18:1) concentration in beef was increased by feeding sunflower oil or seeds, linseed, and soybean oil supplemented diets, while cattle fed linseed and fish oil supplemented diets had increased concentrations of EPA and DHA. Although the concentration of these fatty acids can be increased in beef, there is a need to further the understanding of the mechanism by which they exert positive affects on human health. De la nourriture, les animaux tirent maints acides gras essentiels comme les acides linoléique et linolénique. On sait que ces acides gras et leurs isomères modifiés ou des molécules plus longues sont également bénéfiques à la santé humaine. À l'heure actuelle, on a reconnu les effets bénéfiques de deux isomères des acides linoléiques conjugués (le cis-9, trans-11 C18:2 et le trans-10, cis-12 C18:2) et de deux formes allongées de l'acide linolénique [l'acide eïcosapentaénoïque (EPA, C20:5 n-3) et l'acide docosahexaénoïque (DHA, C22:6 n-3) sur la santé humaine. Les consommateurs peuvent obtenir ces acides gras fonctionnels du boeuf si on modifie l'alimentation des bovins pour leur fournir les acides gras précurseurs. Le régime, la race et le genre sont des facteurs importants qui affectent la concentration totale de lipides et la composition des acides gras dans la viande (ALC, EPA et DHA). La nourriture fournit les acides gras précurseurs, qui sont modifiés et déposés dans les tissus, tandis que la race dicte l'importance des dépôts lipidiques. On peut accroître la concentration de ces acides gras dans le boeuf en relevant le rapport fourrages:concentrés, en utilisant des fourrages non fermentés et en employant divers oléagineux ou huiles comme supplément. L'huile ou les graines de tournesol, de lin et...