Table 2. Over time impacts of N2 and Ar flushing on rumen pH, TGP, NH3-N and VFA production

Items 3 h 9 h 12 h 24 h RMSE p-value1)
Ar N2 Ar N2 Ar N2 Ar N2 Gas Time × Gas
pH 7.02 7.01 6.78 6.79 6.70 6.70 6.59 6.59 0.017 0.634 0.793
TGP (mL) 22.88 25.96 42.09 43.62 48.84 51.12 65.22 68.15 1.663 < .001 0.781
CH4 (mL) 2.66 2.74 7.98 8.20 9.89 9.98 14.35 14.87 0.340 0.078 0.552
NH3-N (mg/dL) 8.24 10.66 9.38 9.88 10.56 12.30 18.96 24.65 1.897 0.001 0.081
TVFA (mM) 39.33 39.36 52.66 52.22 58.16 58.73 75.41 75.66 1.010 0.700 0.779
 Acetate (mM) 25.51 25.55 34.80 34.43 38.34 38.84 49.50 49.72 0.702 0.574 0.751
 Propionate (mM) 8.27 8.26 10.79 10.70 11.97 12.02 15.35 15.46 0.192 0.669 0.686
 Butyrate (mM) 3.70 3.71 4.79 4.75 5.26 5.29 6.69 6.73 0.089 0.760 0.837
 Iso-butyrate (mM) 0.41 0.40 0.51 0.49 0.52 0.53 0.90 0.85 0.025 0.100 0.166
 Valerate (mM) 0.67 0.67 0.85 0.84 0.91 0.91 1.20 1.17 0.023 0.160 0.488
 Iso-valerate (mM) 0.77 0.77 1.03 1.01 1.13 1.12 1.77 1.73 0.027 0.145 0.570
 A:P ratio 3.09 3.09 3.22 3.22 3.21 3.23 3.22 3.22 0.019 0.456 0.396
p-value for time factor were < 0.001 in all items.
N2, nitrogen gas; Ar, argon gas; TGP, total gas production; NH3-N, ammonia nitrogen; VFA, volatile fatty acids; RMSE, root of mean square error; TVFA, total volatile fatty acids; sum of acetate propionate, butyrate, iso-butyrate, valerate and iso-valerate concentration (mM); A:P ratio, acetate and propionate ratio.