Classification Methods and Common Types of Rice Bran

Rice is one of humanity's main food grains, and rice is rarely used to feed livestock. What serves as feed is mainly the by-product of processing rice into milled rice - rice bran, whose nutritional value varies greatly depending on the processing method.

Due to differences in rice processing methods, rice bran can be divided into rice hulls, rice bran, and rice mill by-product.

Rice hulls are the husk (glume) powder removed when rice is processed into brown rice, amounting to about 20% of the rice's mass, with crude fiber at 44.5%, of which lignin is 21.4%; the digestible energy (2.006MJ per cow, 0.907MJ/k per pig) is very low, and the digestible protein is a negative value, so it is purely roughage.

Rice bran is the by-product of refining brown rice into polished rice, composed of the seed coat, aleurone layer, embryo, and a small amount of endosperm, accounting for 6%-8% of the rice. Rice bran can not only serve as feed, but because of its high fat content, humans can also extract edible oil from rice bran. Rice bran that has not been pressed for oil, due to its relatively high unsaturated fat content, is prone to rancidity and is not easy to preserve.

There are two types of rice mill by-product. One is the mixture of rice hulls (rice hulls), broken rice, and rice bran separated when producing milled rice from rice through a single processing method; this type of bran accounts for about 25%-30% of the rice, and its nutritional value falls between rice hulls and rice bran. The digestible energy of its dry matter is 6.730MJ/kg for sheep and 3.846-5.894MJ/kg for pigs; therefore, it should be classified as roughage. The other type is made by artificially mixing the rice bran separated during processing with rice hulls. Depending on the mixing ratio, it can be further divided into 10% rice bran 90% rice hulls rice mill by-product, 20% rice bran 80% rice hulls rice mill by-product, 30% rice bran 70% rice hulls rice mill by-product, etc. The composition and nutritional value of rice mill by-product depend on the ratio of rice hulls to rice bran. The higher the proportion of rice hulls, the poorer the nutritional value. Rice mill by-product with a high proportion of rice hulls should be classified as roughage.

Rice bran has a high oil content and is not easy to preserve. Rice bran after oil extraction is defatted rice bran.