What are the classification methods for rice bran? A detailed explanation of common types

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

Depending on the rice processing method, rice bran can be divided into rice hulls, rice bran and rice mill by-product.

Rice hulls are the husk (glume) powder removed when processing rice into brown rice. Their amount is about 20% of the rice mass. They contain 44.5% crude fiber, of which 21.4% is lignin. Their digestible energy (2.006MJ/kg for cattle, 0.907MJ/kg for pigs) is very low, and their digestible protein is negative, so they are purely a roughage.

Rice bran is the by-product of refining brown rice into polished rice. It consists 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 be used as feed, but because of its high fat content, humans can also extract edible oil from rice bran. Rice bran that has not been oil-extracted is prone to rancidity and difficult to preserve because of its relatively high unsaturated fat content.

Rice mill by-product has two types. One is the mixture of rice hulls, broken rice and rice bran separated when producing polished rice from rice by a single processing method. This kind of bran accounts for about 25%-30% of the rice, and its nutritional value lies between rice hulls and rice bran. Its digestible energy of dry matter is 6.730MJ/kg for sheep and 3.846-5.894MJ/kg for pigs, so it should belong to roughage. The other is made by artificially mixing the rice bran and rice hulls separated during processing. According to the different mixing proportions, 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 belong to roughage.

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