Study On Available Energy And Nutrients Digestibility Of Full-fat Rice Bran For Growing Pigs

Six experiments were conducted to determine the digestibility of energy, amino acids and fatty acids in full-fat rice bran (FFRB) and establish prediction equations to predict their available energy, as well as the digestibility of amino acids and fatty acids. The full-fat rice bran samples were chosen according to their variety, processing method and region of production. The prediction equations were also validated by two different experiments. In Exp.l, more than50production plants were visited for an investigation on the annual production of full-fat rice bran in the main rice production provinces of China. The chemical composition of the full-fat rice bran sample was analyzed. The sheets named "Feed Sample Entity (FSE)" were filled at the same time. The results showed that different sources of full-fat rice bran had significant variation in nutrient contents. The study showed that the more rollers used in the production process, the higher the starch content be found in the full-fat rice bran, as well as a lower content of crude protein and acid hydrolyzed ether extract (AEE). Variation was also caused by different varieties growing in different regions resulting in climate and soil differences, and different processing methods. In Exp.2, the digestible energy (DE) and metabolizable energy (ME) content of full-fat rice bran were determined and prediction equations were established based on their chemical composition. Seventeen full-fat rice bran samples were collected from different provinces around China. Full-fat rice bran samples were used in each treatment to replace30%of the energy-supplying ingredients in the corn-soybean meal based diet. An extra corn diet was used as the inner standardized control. The DE and ME were determined by the total collection method. The results showed that the DE content ranged from14.48to16.85MJ/kg, and the ME content ranged from12.49to15.84MJ/kg. Eight prediction equations were established. The equations with the highest R2were DE=7.78-0.09×CP+0.25×AEE+0.05x ST-0.08x NDF+0.29x ADF-0.13x Ash-1.8x Ca+2.43x TP, R2=0.92and ME=5.00+0.04x CP+0.32x AEE+0.05x ST-0.11x NDF+0.32x ADF+0.19x Ash-5.56x Ca+0.23x TP, R2=0.70. In Exp.3, the equations were validated using a similar method as in Exp.2. Two new full-fat rice bran samples were collected and their DE and ME were predicted by the equations of Exp.2. Then the measured values of DE and ME of the two new full-fat rice bran samples were compared with predicted values to validate and select the best equation. The results showed that the closest predicted value compared with the measured value on ME was obtained by observed from ME=6.22+0.22x CP+0.28x AEE+0.02x ST-0.14x NDF+0.30x ADF, R2=0.61. In Exp.4, the performance of pigs was measued to validate the selected equation from Exp.3. The ME content of a new full-fat rice bran sample was predicted by the equation from Exp.3. The predicted ME was used to formulate4experiment diets which included4levels of full-fat rice bran samples (0,10,20and30%) with the same level of dietary ME (13.82MJ/kg). The results showed that there was no significant difference in F/G among treatments at the same level of dietary ME. In Exp.5, the apparent (AID) and standardized (SID) ileal digestibility of amino acids and AID of fatty acids were determined in10out of the17full-fat rice bran samples used in Exp.2. Two6x6Latin square designs were used. There were eleven diets and six periods. The six diets were comprised of one nitrogen-free diet and five full-fat rice bran test diets in each square. The results showed that there were significant differences in the AID of18amino acids among the10full-fat rice bran samples and significant differences in SID of16amino acids, except glycine and proline. There were significant differences among treatments in the AID of palmitic acid, stearic acid, oleic acid and linoleic acid. The best prediction equation for SID for methionine and lysine of full-fat rice bran were SID Met=107.89+7.82x CP+0.36x ST-1.40x NDF+3.78x ADF-3.68x Ash-6.33x Ash, R2=0.96and SID Lys=60.45-5.28x CP-0.35x ST-1.22x ADF+9.95x Ash+309.80x Met-356.48x Thr+883.68x Trp, R2=0.99. The prediction equation for fatty acid AID of full-fat rice bran could not be established. In Exp.6, the objective was to determine the difference of available energy among the following three ingredients:full-fat rice bran, defatted rice bran (DFBR) and defatted rice bran with added oil (DFRB+RBO). The full-fat rice bran, defatted rice bran and DFRB+RBO samples were obtained from a specific batch from a plant. A total of9test diets were made including3full-fat rice bran diets,3defatted rice bran diets and3DFRB+RBO diets. Each ingredient was added in the basal diet at levels of10,30and50%, to determine the DE and ME content in the three ingredients. The results showed that the DE and ME of the full-fat rice bran and DFRB+RBO increased linearly with increasing levels of the respective ingredient. The ME of full-fat rice bran was higher than defatted rice bran, and the differences were1.02(10%),3.24(30%), and3.21MJ/kg (50%), respectively. The ME of full-fat rice bran was lower than DFRB+RBO, and the differences were0.90(10%),1.67(30%) and1.22MJ/kg (50%).