Flax is a cool climate crop grown mainly for production of fiber and food. Its seed, linseed, is rich in oil which contains more than 50% of the essential fatty acid alfa-linolenic acid (omega-3). Linolenic acid is converted into eicosapentaenoic acid and docosahexaenoic acid, precursors of eicosanoids such as prostaglandins. Moreover, linseed is one of the richest sources of lignans, a phytoestrogen. Supplementing linseed to dairy cows increases omega-3 acid content in plasma and reproductive tissues, which can affect the development of ovarian follicles and corpus luteum.