Table 3.
Effect of increasing levels of biocarbon on fermentation and gas production in the RUSITEC
| Item | Level of biocarbon (% of diet DM) | P value | ||||||
|---|---|---|---|---|---|---|---|---|
| 0 | 0.5 | 1.0 | 2.0 | SEM | Linear | Quadratic | 0 vs. All | |
| pH | 6.8 | 6.9 | 6.8 | 6.8 | 0.04 | 0.66 | 0.41 | 0.49 |
| NH3-N, mmol/d | 6.6 | 7.0 | 7.1 | 7.3 | 0.40 | 0.06 | 0.48 | 0.06 |
| Total VFA, mmol/d | 61.0 | 61.3 | 64.2 | 68.5 | 1.44 | 0.005 | 0.54 | 0.02 |
| VFA, mmol/d | ||||||||
| Acetate (A) | 34.7 | 34.1 | 36.4 | 39.0 | 1.84 | 0.001 | 0.38 | 0.10 |
| Propionate (P) | 14.1 | 14.6 | 15.4 | 16.6 | 0.45 | 0.001 | 0.98 | 0.008 |
| Butyrate | 7.1 | 7.7 | 7.3 | 8.1 | 0.49 | 0.02 | 0.70 | 0.06 |
| BCVFA1 | 1.76 | 1.75 | 1.84 | 2.0 | 0.06 | 0.001 | 0.29 | 0.08 |
| Valerate | 2.40 | 2.62 | 2.48 | 2.36 | 0.58 | 0.58 | 0.34 | 0.63 |
| Caproate | 0.73 | 0.69 | 0.68 | 0.69 | 0.70 | 0.45 | 0.46 | 0.26 |
| A:P | 2.42 | 2.35 | 2.36 | 2.38 | 0.08 | 0.66 | 0.29 | 0.24 |
| Gas production, L/d | 2.18 | 1.92 | 2.15 | 2.04 | 0.08 | 0.63 | 0.57 | 0.14 |
| CH4, % of gas | 7.4 | 6.8 | 6.8 | 6.9 | 0.68 | 0.02 | 0.03 | 0.001 |
| CH4, mg/d | 110.8 | 82.8 | 95.3 | 90.7 | 9.23 | 0.07 | 0.05 | 0.002 |
| CH4, g/g DM incubated | 11.1 | 8.3 | 9.5 | 8.9 | 0.92 | 0.04 | 0.05 | 0.001 |
| CH4, g/g DM digested | 15.2 | 11.0 | 12.8 | 11.8 | 1.22 | 0.06 | 0.03 | 0.001 |
| Protozoa, ×104/mL | 5.2 | 4.3 | 6.1 | 5.5 | 0.41 | 0.21 | 0.68 | 0.91 |
A:P = acetate to propionate ratio.
1Branched-chain volatile fatty acids (isobutyrate + isovalerate).