After corn and wheat, rice is the third most widely grown cereal grain worldwide. Most rice is processed to produce polished white rice for human consumption, and several co-products result from this processing. First, the outer husk, or hull, of the grain is removed. The dehulled grain, consisting of the bran, germ, and endosperm, is brown rice. To produce white rice, the brown rice is milled further and the bran is removed. Rice bran is high in fiber, and also contains about 15% crude protein and 14 to 20% fat. Rice bran can be fed as full fat rice bran or defatted rice bran. Rice bran is sometimes combined with rice hulls to produce rice mill feed. During milling of the rice, some kernels may get broken and cannot be used for human consumption. These broken kernels are known as broken rice or brewers rice and may also be used in animal feeding.

The phosphorus content of rice is similar to that of corn. Most of the phosphorus in rice is in the bran fraction, and 80-85% of the phosphorus in rice bran is bound to phytate, which limits its digestibility by pigs. Microbial phytase can be used in swine diets to increase the digestibility of phytate-bound phosphorus. However, limited information exists about phosphorus digestibility in rice co-products and how it is affected by microbial phytase. Therefore, an experiment was conducted to determine the apparent (ATTD) and standardized (STTD) total tract digestibility of phosphorus in brown rice, broken rice, full fat rice bran (FFRB), defatted rice bran (DFRB), and rice mill feed fed to growing pigs. A second objective of the experiment was to determine the effect of microbial phytase on phosphorus digestibility in rice co-products.