Available energy and nutrient apparent total tract digestibility of full-fat rice bran fed to gestating and lactating sows.

The substitution method was used to design four substitution levels (15%, 25%, 35%, 45%) in Exp. 1 and three substitution levels (15%, 25%, 35%) in Exp. 3, to determine the appropriate level of full-fat rice bran (FFRB) for replacing energy-supplying components in the basal diet for gestating sows (Exp. 1: gestation day, 35 ± 5 d; body weight, 194.6 ± 12.1 kg; parity, 3-4) and lactating sows (Exp. 3: body weight, 252.4 ± 13.6 kg; parity, 3-6). Based on optimal substitution levels identified in Exp. 1 and 3, test diets were formulated for Exp. 2 and 4, respectively. The available energy values of five FFRB sources (Exp. 2) and four FFRB sources (Exp. 4) were evaluated in gestating sows (gestation day, 35 ± 5 d; body weight, 197.9 ± 5.3 kg; parity, 3-4) and lactating sows (body weight, 270.0 ± 25.4 kg; parity, 3-6), respectively. Predictive equations for the available energy of FFRB were established for both reproductive stages. For gestating sows, the 35% substitution level group achieved the highest net energy (NE) value, with significantly greater energy retention as lipid (REL) compared with other substitution groups (P < 0.05). Additionally, the group exhibited the lowest coefficient of variation (CV) for digestible energy (DE), metabolizable energy (ME), and NE values. Therefore, a 35% substitution level of FFRB for energy components in the basal diet was optimal for gestating sows using the substitution method. For lactating sows, the 25% substitution level was optimal based on the lowest CV for DE and ME values. Lactating sows demonstrated greater nutrient digestibility than gestating sows; however, the energy utilization of FFRB was higher in gestating sows. In gestating sows, the DE values of five FFRB sources ranged from 15.22 to 15.90 MJ/kg dry matter (DM), ME values from 14.63 to 15.29 MJ/kg DM, and NE values were 10.77, 11.97, 12.58, 11.55, and 11.45 MJ/kg DM. In lactating sows, DE ranged from 13.28 to 13.97 MJ/kg DM, and ME from 11.13 to 12.19 MJ/kg DM. Fiber, ether extract (EE), and crude protein (CP) were predominant predictors of available energy of FFRB for sows. The predictive equations for DE, ME, and NE of FFRB in gestating sows were as follows: DE = 0.42 EE - 0.09 NDF + 11.20 (R² = 0.71, P < 0.01); ME = 0.70 DE - 0.02 Ash + 4.24 (R² = 0.79, P < 0.01); NE = 0.05 ST - 0.37 ADF + 14.75 (R² = 0.85, P < 0.01).The predictive equation for ME of FFRB in lactating sows was: ME = 1.12 DE + 0.06 CP - 0.03 NDF - 3.86 (R2 = 0.97, P < 0.01).