Rape seed (Brassica napus), also known as Rape, Oilseed Rape, Rapa, Rapaseed and (one particular variety) Canola, is a bright yellow flowering member of the family Brassicaceae (mustard or cabbage family). The name is derived through Old English from a term for turnip, rapum (see Brassica napobrassica, which may be considered a variety of Brassica napus). Natural rape seed oil contains erucic acid, which is mildly toxic to humans in large doses but is used as a food additive in smaller doses. Canola, originally a syncopated form of the abbreviation "Can.O., L-A." (Canadian Oilseed, Low-Acid) that was used by the Manitoba government to label the seed during its experimental stages, is now a tradename for low erucic acid rapeseed that is sometimes mis-applied to other varieties[citation needed]. The rape seed is the valuable, harvested component of the crop. The crop is also grown as a winter-cover crop. It provides good coverage of the soil in winter, and limits nitrogen run-off. The plant is ploughed back in the soil or used as bedding. On some ecological or organic operations, livestock such as sheep or cattle are allowed to graze on the plants.