Table 5.
Gas production and fermentation parameters of experimental diets containing 40% of alfalfa hay and 60% of concentrate with increased amounts of Brussels sprouts (BS; 8, 16, and 24% of concentrate).
| Item | Diet | SEM 2 | p | ||||
|---|---|---|---|---|---|---|---|
| Control | BS8 | BS16 | BS24 | Lineal | Quadratic | ||
| Gas production parameters 1 | |||||||
| A (mL/g DM) | 280 a | 289 ab | 290 ab | 293 b | 3.47 | 0.027 | 0.388 |
| c (%/h) | 3.90 | 4.00 | 4.00 | 3.99 | 0.061 | 0.449 | 0.330 |
| Lag (h) | 1.10 | 0.87 | 0.62 | 0.64 | 0.21 | 0.126 | 0.574 |
| AGPR (mL/h) | 7.40 | 7.98 | 8.06 | 8.09 | 0.21 | 0.053 | 0.239 |
| DMED (%) | 40.6 | 41.9 | 42.2 | 41.9 | 0.62 | 0.147 | 0.214 |
| Fermentation parameters (8 h) | |||||||
| Total volatile fatty acids (VFA; µmol) | 1284 a | 1391 ab | 1501 bc | 1561 c | 34.8 | <0.001 | 0.512 |
| Individual VFA (mol/ 100 mol) | |||||||
| Acetate (Ac) | 61.1 | 61.6 | 61.3 | 61.7 | 0.17 | 0.152 | 0.822 |
| Propionate (Pr) | 22.9 a | 22.9 a | 23.3 b | 23.6 b | 0.11 | 0.001 | 0.384 |
| Butyrate | 12.8 c | 12.5 bc | 12.3 b | 11.8 a | 0.12 | <0.001 | 0.582 |
| Minor VFA 3 | 3.11 | 3.01 | 3.04 | 2.95 | 0.061 | 0.141 | 0.929 |
| Ac/Pr (mol/mol) | 2.69 b | 2.71 b | 2.64 ab | 2.63 a | 0.022 | 0.019 | 0.454 |
| NH3-N (mg/L) | 143 a | 148 ab | 154 b | 155 b | 2.9 | 0.033 | 0.560 |
| CH4 (mL) | 6.90 | 7.24 | 7.02 | 7.36 | 0.330 | 0.453 | 0.991 |
| CH4/VFA (mL/mmol) | 5.40 | 5.22 | 4.68 | 4.71 | 0.311 | 0.092 | 0.739 |
| AFOM (%) 4 | 31.3 a | 33.4 ab | 36.3 bc | 37.9 c | 0.84 | <0.001 | 0.474 |
| Fermentation parameters (24 h) | |||||||
| pH | 6.79 b | 6.75 ab | 6.74 a | 6.73 a | 0.01 | 0.004 | 0.394 |
| Total VFA (µmol) | 2446 a | 2650 b | 2673 b | 2684 b | 0.1 | <0.001 | 0.008 |
| Individual VFA (mol/ 100 mol) | |||||||
| Acetate (Ac) | 61.5 | 61.6 | 61.5 | 61.7 | 28.36 | 0.342 | 0.583 |
| Propionate (Pr) | 18.7 a | 19.0 ab | 19.3 b | 19.6 b | 0.12 | <0.001 | 0.788 |
| Butyrate | 15.5 d | 14.9 b | 14.7b | 14.1 a | 0.14 | <0.001 | 0.931 |
| Minor VFA 3 | 4.27 a | 4.53 ab | 4.53 ab | 4.57 b | 0.092 | 0.048 | 0.217 |
| Ac/Pr (mol/mol) | 3.31 c | 3.28 bc | 3.20 ab | 3.16 a | 0.0143 | 0.003 | 0.962 |
| NH3-N (mg/L) | 189 | 203 | 207 | 209 | 6.1 | 0.090 | 0.506 |
| CH4 (mL) | 14.9 | 15.1 | 14.8 | 15.2 | 0.41 | 0.804 | 0.846 |
| CH4/VFA (mL/mmol) | 6.10 b | 5.69 ab | 5.53 a | 5.65 a | 0.140 | 0.039 | 0.095 |
| AFOM (%) 4 | 60.5 a | 64.0 b | 65.1 b | 65.4 b | 0.66 | 0.001 | 0.007 |
a, b, c Means in the same row with different superscript differ (p < 0.05); 1 A: potential gas production; c: fractional rate of gas production; Lag: is the time needed to start gas production; AGPR: average gas production rate; DMED: dry matter effective degradability estimated for a rumen particulate outflow 0.042 per h; 2 SEM: standard error of the mean; 3 Minor VFA: calculated as the sum of isobutyrate, isovalerate, and valerate; 4 AFOM: fermented organic matter estimated from VFA production as proposed by Demeyer [25].