Table 1. Equations used to estimate some in vitro parameters and their derivatives
No.
Equations
Source
1
SCFA = 0.0222 GP-0.00425
Getachew et al., 2002
2
PF = DMD (mg)/ gas produced (ml) in vitro at 24h
Getachew et al., 1998
3
ME = 2.20 + 0.136 Gas24h + 0.057CP + 0.0029CF2, for forage
Menke and Stengass, 1988
feeds
4
ME = 1.06 + 0.157 GP + 0.084 CP + 0.22 CF - 0.081 CA for
Menke and Stengass, 1988
concentrate feeds
5
OMD =148.8 + 8.89GP + 4.5CP(g/kg DM) + 0.651ash(g/kg DM)
Menke et al., 1979
6
Gas yield = ml gas per g DM/g DMD
Salem et al. (2013) and
Elghandour et al. (2017)
7
MCP=mg DMD-(mL gas×2.2 mg mL-1), where 2.2 mg mL-1 is a
Blümmel et al., 1997
stoichiometric factor which indicates mg of H, C, and O essential
for the production of 1 mL of gas
SCFA (mmol 200 mg-1 DM): short-chain fatty acids; DM: dry matter; GP: 24 h net gas production (mL 200
mg-1 DM); PF (mg/ml): partition factor; DMD (%DM): dry matter disappearance; ME (MJ/kg DM):
metabolizable energy; CF: crude fiber; CA: crude ash (%DM); OMD (g/kg of OM): In vitro organic matter
digestibility; MCP (mg g-1 DM): microbial crude protein
Table 2. Equations used by CNCPS to calculate protein fractions (Higgs et al., 2015)
Fraction
Description
Equation1
A1
Ammonia
Ammonia × (SP/100) × (CP/100)
A2
Soluble true protein
SP × CP/100 − A1
B1
Insoluble true protein
CP − (A1 − A2 − B2 − C)
B2
Fibre-bound protein
(NDICP − ADICP) × CP / 100
C
Indigestible protein
ADICP × CP / 100