Grits are not all the same! For a start there is soluble grit and insoluble grit.
- Soluble Grit
Soluble grit serves a different function to insoluble grit. Soluble grit is soft and rapidly dissolves in a bird's "stomach". Soluble grit is usually in the form of shellgrit.
Soluble grit is a good dietary source of calcium and various trace minerals. Mineral blocks and cuttle bone are other sources of dietary calcium and trace minerals. However soluble
grit is not very useful for grinding hard seeds to a paste.
- Insoluble Grit
As its name suggests, insoluble grit is largely insoluble, and therefore any minerals it might contain are not available to be used as bird building blocks. Insoluble grit serves a
similar purpose to teeth in those birds that need to grind seeds and other food to a fine paste. However, this grinding process does not take place in the mouth. Instead, the grit
accumulates in the muscular gizzard of those birds which have one, and as food passes between bits of grit, they become ground into a paste. (Another name for the gizzard is the
ventriculus.) Examples of insoluble grits include crushed sandstone, beach sand, river sand and various gravels.
