Table 4.
The calculation equations used in the present study.
| Numbers | Equations |
|---|---|
| 1 | TRN (g/bird/D)1 = Ni-Ne |
| 2 | RNegg (g/bird/D)2 = 1.936 × Egg mass |
| 3 | RNbody (g/bird/D)3 = TRN-RNegg |
| 4 | AMEdiet (kcal/kg DM)4 = (GEi-GEe)/FI |
| 5 | AMEndiet (kcal/kg DM)5 = AME-[8.22 × TRN]/FI |
| 6 | AMEI (kcal/brid/D)6 = AME × FI |
| 7 | HP (kcal)7 = 3.866 × VO2 (L) + 1.200 × VCO2 (L) |
| 8 | NEdiet (kcal/kg DM)8 = (AMEI-HI)/FI |
| 9 | RE (kcal/brid/D)9 = AMEI-HP |
| 10 | REprotein (kcal/bird/D)10 = TRN × 6.25 × 5.7 |
| 11 | REfat (kcal/bird/D)11 = RE-REprotein |
| 12 | AMEcorn (kcal/kg DM)12 = reference diet AME-[(reference diet AME-test diet AME)/percentage of substitution rate (DM)]; |
| 13 | AMEncorn (kcal/kg DM)13 = reference diet AMEn-[(reference diet AMEn-test diet AMEn)/percentage of substitution rate (DM)]; |
| 14 | NEcorn (kcal/kg DM)14 = reference diet NE-[(reference diet NE-test diet NE)/percentage of substitution rate (DM)]. |
TRN is the total retained nitrogen, Ni is the nitrogen intake from diet (g/bird/D), and Ne is the nitrogen output from excreta (g/bird/D).
RNegg is the total retained nitrogen in the egg (g/bird/D), 1.936 is N% in the egg (Miranda et al., 2015).
RNbody is the total retained nitrogen in body (g/bird/D).
AMEdiet is the AME value of the diet. GEi and GEe are the gross energy intake (kcal/bird/D) from the diet and the gross energy output from excreta (kcal/bird/D), respectively. FI is the feed intake (g/bird/D DM).
AMEndiet is the AMEn value of the diet. 8.22 is the nitrogen correction factor for each gram of nitrogen retained in the body and in eggs (kcal/g; Hill and Anderson, 1958).
AMEI is the AME intake.
HP is the heat production calculated using the following equation, proposed by Brouwer (1965), without correction for methane and nitrogen in expired gas. VO2 and VCO2 are volumes of O2 and CO2, respectively.
NEdiet is the NE value of the diet. HI is heat increment calculated by subtracting FHP from HP. The FHP value of 88 kcal/kg BW0.75 per bird per day for laying hens reported by Wu et al. (2016) was used in the calculation. This FHP value corresponds to the asymptotic HP (at zero activity) after a 24-h fasting period.
RE is the retained energy.
REprotein is the retained energy as protein. 6.25 is the protein equivalent of 1 g nitrogen, and 5.7 is the energy equivalent of 1 g protein (kcal/kg/D).
REfat is the retained energy as fat.
AMEcorn is the AME value of the corn sample.
AMEncorn is the AMEn value of the corn sample.
NEcorn is the NE value of the corn sample.