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Table 2 Effect of diets and incubation time on pH, ammonia N concentration, volatile fatty acid production (VFA) and molar proportions of acetate, propionate, butyrate and other VFA

From: Influence of main dietary chemical constituents on the in vitro gas and methane production in diets for dairy cows

  pH Ammonia N, mg/L VFA, mmoL/L Acetate (Ac), % VFA Propionate (Pr), % VFA Ac:Pr Butyrate, % VFA Other VFA, % VFA
Diet
 Reference 6.87 202 5.08 56.1 23.5 2.40 16.0 4.47
 Low NDF 6.88 192 5.37 55.8 23.7 2.36 16.2 4.29
 High NDF 6.90 223A 4.44 58.5A 23.1 2.53 13.3B 4.26B
 Low CP 6.85 171 5.06 56.0 24.3 2.31 16.1 3.71B
 High CP 6.87 222A 4.89 57.2 22.8 2.51 14.6 4.85A
 Low lipid 6.87 207 4.96 56.4 23.7 2.39 15.5 4.26B
 High lipid 6.90 197 4.99 56.7 23.5 2.41 15.4 4.36
  SEM 0.043 28.5 0.231 0.25 0.64 0.062 0.91 0.158
   P-value 0.46 0.008 0.25 <0.001 0.06 0.001 0.002 <0.001
P-value of contrasts
 Low vs High NDF 0.99 0.44 0.23 <0.001 0.99 0.001 0.004 0.99
 Low vs High CP 0.99 0.014 0.99 0.048 0.048 <0.001 0.99 <0.001
 Low vs High lipid 0.99 0.99 0.99 0.99 0.99 0.65 0.99 0.99
Incubation time
 24 h 6.95 202 4.47 57.2 22.9 2.50 15.8 3.87
 48 h 6.80 202 5.47 56.1 24.1 2.33 14.7 4.76
  SEM 0.055 38.7 0.123 0.13 0.82 0.077 1.15 0.201
   P-value 0.31 0.99 0.029 0.026 0.39 0.26 0.58 0.09
RMSE 0.032 17.5 0.462 0.49 0.60 0.112 0.87 0.147
  1. Values with different superscripts within column are significantly (P < 0.05) higher (A) or lower (B) compared to the reference diet (containing 361, 158, and 33 g/kg DM of NDF, CP, and lipids)
  2. Low NDF low NDF diet (325 g/kg DM); High NDF high NDF diet (435 g/kg DM), Low CP low protein diet (CP, 115 g/kg DM), High CP high protein diet (CP, 194 g/kg DM), Low lipid low lipid diet (EE, 26 g/kg DM), High lipid high lipid diet (EE, 61 g/kg DM)