Pigs cannot digest whole grains. A correct grind coarseness of grains improves feed efficiency and reduces the separation of feed, making the pigs' feed portions more even.
Suitable grind coarseness
The grains used in meat pigs' feed mixtures should be ground relatively fine:
< 1 mm 60% of volume
1-2 mm 40% of volume
Grinding grains that were stored fresh in airtight silos is more difficult than grinding grains that were stored dry and it may not be possible to reach the above mentioned particle size distribution, especially when the moisture content of fresh grains is over 20%.
The optimal grind coarseness depends on the peel thickness of the grain: grains with thin peels such as wheat and Triticale can be ground more coarsely than grains with thick peels. Too coarse grinding decreases for example the tastiness and digestivity of barley which may have a huge economic impact on pork production. On the other hand, too fine grinding increases the risk of gastric ulcers and tail biting.
Purchasing two mills for large farms is a lucrative acquisition because various feeds can be ground using suitable grind coarsenesses.
In order to prevent separation, other components should be ground at least as fine as grains. For example, protein groats and cakes must be ground, as well as peas and horse beans. In order to improve protein digestibility, protein ingredients should be ground as fine as possible.