Linseed oil cake is an animal feed that is used to produce oil. Linseed is a type of seed that is ground into a powder. The oil cake is made by grinding linseed into a powder, and then mixing it with water and heating it until it is a liquid. The liquid is then filtered out of the powder, leaving a cake that is around 30% moisture and 15% protein. The liquid cake is then added to animal feed. The cake is most often used as a protein supplement for ruminants, but can also be fed to monogastric animals like pigs.