Enrichment of ruminant products with nutritionally beneficial fatty acids

Consumers are increasingly becoming more aware of the relationships between diet and health. The functional–food components of beef and milk fat include ω–3 polyunsaturated fatty acids (PUFA) and conjugated linoleic acid (CLA). Beef typically has high saturated fatty acid content and low PUFA content, but the content of beneficial fatty acids can be increased by dietary manipulation. Dietary linseed (rich in ω–3 PUFA α–linolenic acid, 18:3n–3) can double the contents of 18:3n–3 and eicosapentaenoic acid (EPA, 20:5n–3) in muscle and adipose tissue, resulting in a lower n–6:n–3 ratio. Beef from grass–fed animals beef has higher levels of 18:3n–3, EPA and docasahexaenoic acid (22:6n–3) than that from concentrate–fed animals. Protection of dietary PUFA from ruminal biohydrogenation results in further enhancement of the PUFA content of meat. The main CLA isomer in beef is cis–9, trans–11 CLA, which is mainly associated with the neutral lipid fraction; the concentration of this isomer is thus positively correlated with the degree of fatness. PUFA–rich diets increase the content of cis–9, trans–11 CLA in beef. As the dietary content of n–3 PUFA increases, undesirable sensory attributes such as ‘greasy’ and ‘fishy’ increase and colour and shelf life may be reduced, necessitating the use of higher levels of dietary antioxidants. These nutritional strategies provide mechanisms for increasing the content of health–promoting fatty acids in beef.