Plants are the primary source of omega-3 polyunsaturated fatty acids (PUFA) in the land and marine food chains and provide the basis to produce milk and meat with enhanced nutritional attributes. This chapter describes the range of omega-3 PUFA sources used in animal feeding – including forages, oilseeds and fish oils – and identifies the factors controlling the incorporation of omega-3 PUFA into milk and meat. There is a particular focus on the challenges of increasing omega-3 PUFA in ruminant products as a consequence of rumen biohydrogenation, as well as limitations on elongation/desaturation of omega-3 PUFA and on incorporation of the longer chain omega-3 PUFA into triacylglycerols. The chapter also considers the implications of seeking to modify omega-3 PUFA in products for livestock health and fertility, as well as for product quality attributes such as flavour and shelf-life.