Global production of rice is third in terms of total tonnage after corn and wheat. Rice is grown to produce polished white rice for human consumption. However, harvested rice, called paddy rice or rough rice, needs to be dehulled, which results in production of brown rice. The outer brown bran layer of brown rice, known as rice bran, also needs to be removed before polished white rice is produced. Approximately 20% of the paddy rice is hulls and the bran fraction is 8 to 10%, so only 70% of the paddy rice will become polished rice. 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. 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. Broken rice is high in starch and contains little fat, fiber, or protein.

Both rice bran and broken rice may be fed to pigs, but these ingredients are poorly characterized in terms of nutritional value. An experiment was, therefore, conducted to determine the standardized ileal digestibility (SID) of crude protein and amino acids in broken rice, two sources of full fat rice bran (FFRB), and defatted rice bran (DFRB) fed to growing pigs.

Seven growing pigs with an average initial body weight of 70.07 kg were fed one of six diets. The control diet was based on bakery meal, which is a mixture of by-products from the bakery and confectionary industries. Bakery meal was used because it is highly palatable to pigs. Four diets were formulated by mixing bakery meal with one of four rice co-products: broken rice, two sources of FFRB, and one source of DFRB. A nitrogen-free diet that was used to determine endogenous losses of crude protein and amino acids was also formulated. Because none of the diets contained sufficient amino acids to meet the requirements for growing pigs, an amino acid mixture was fed to the pigs in the adaptation periods to the diets. The apparent ileal digestibility of amino acids in the experimental ingredients was calculated using the difference procedure, and adjusted for endogenous losses to calculate standardized ileal digestibility.

The SID of crude protein and all amino acids was greatest (P <0.01) in broken rice compared with the rice bran products (Table 2). This is likely due to the lower concentration of fiber in broken rice. The SID of crude protein was greater (P <0.01) in FFRB-1 than in FFRB-2, but the average SID of indispensable amino acids and of all amino acids did not differ between the two sources of FFRB. The SID of crude protein was the same in DFRB as in FFRB-2, but the mean SID of indispensable amino acids and of all amino acids was less (P <0.01) in DFRB than in the 2 sources of FFRB.

Although digestibility of amino acids was less in DFRB than in the other rice co-products, the relatively high concentration of crude protein and amino acids in DFRB (Table 1) meant that it had the greatest (P <0.001) concentration of standardized ileal digestible amino acids of the test ingredients (Table 3). The concentration of SID crude protein and amino acids was not different between FFRB-1 and FFRB-2. Broken rice, which has a low concentration of crude protein and AA, had the least (P <0.01) SID of crude protein and amino acids despite the high digestibility of amino acids in this product.

• The SID of crude protein and amino acids in broken rice was greater than in the rice bran products.
• Due to its higher fat content, FFRB had greater digestibility of amino acids compared with DFRB.
• Because of its relatively high protein content, the concentration of standardized ileal digestible crude protein and amino acids is greatest in DFRB. Broken rice contains less SID crude protein and amino acids than any of the rice bran products.

Table 1. Analyzed nutrient composition (as-fed basis) of broken rice, full fat rice bran (FFRB-1 and FFRB-2), and defatted rice bran (DFRB)

Table 2. Standardized ileal digestibility (%) of CP and AA in broken rice, two sources of full fat rice bran (FFRB-1 and FFRB-2) and defatted rice bran (DFRB)

 ^a-dMeans within a row lacking a common superscript letter are different (P < 0.05).

¹Values for Pro were not included in the calculated mean for dispensable AA.

Table 3. Concentrations (g/kg DM) of standardized ileal digestible CP and AA in broken rice, two sources of full fat rice bran (FFRB-1 and FFRB-2) and defatted rice bran (DFRB)

^a-dMeans within a row lacking a common superscript letter are different (P < 0.05).

This report is based on unpublished research by Gloria Casas-Bedoya and Hans H. Stein.