Determination and prediction of amino acid digestibility in rice bran for growing pigs.

Objective: This experiment was conducted to determine the apparent ileal digestibility (AID) or standardized ileal digestibility (SID) of crude protein (CP) and amino acids (AA) in 10 rice brans fed to pigs, and to construct predictive models for the SID of CP and AA based on the chemical composition of rice bran.

Methods: Twenty-two healthy [Duroc × (Landrace × Yorkshire)] pigs equipped with ileal T-cannulas (initial body weight: 30 ± 1.5 kg) were selected for this experiment. A replicated 11 × 3 incomplete Latin square design was adopted. The experiment consisted of 3 periods each lasting for 7 days and had 11 dietary treatment groups. The diets included 10 rice bran diets as well as a nitrogen-free diet for determining endogenous losses of AA, and each treatment group had 6 replicates. Titanium dioxide was added to each diet as an indicator at a concentration of 0.3%.

Results: Except for dry matter (DM) and total phosphorus (TP), the coefficients of variation for the chemical components among 10 rice bran sources were all greater than 10%. The SID of CP, Lys, Met, Thr, and Trp in rice bran was 81.89% ± 6.23, 80.33% ± 2.21, 83.25% ± 5.51, 79.89% ± 5.68, and 72.12% ± 4.71, respectively. The best prediction equations for the SID of CP and four limiting AA in rice bran are as follows: SIDCP=974.032-29.805TP-9.496DM (R2=0.88), SIDLys=471.278-9.267TP-4.245DM+1.401dummy variable (R2=0.92), SIDMet=122.281-2.712CP (R2=0.51), SIDThr=51.864+2.204GE-1.324CF [(R2=0.97); GE, gross energy; CF, crude fiber], and SIDTrp= 73.912-23.268Calcium-0.0.336NDF+0.318TS [(R2=0.96); NDF, neutral detergent fiber; TS, total starch].

Conclusion: There was significant variability among the chemical components of 10 different sources of rice bran. Moreover, GE, DM, CP, TP, TS, CF, and NDF could serve as crucial predictors for the SID of AA.