Table 2.
Fermentation gas parameters and energy connected with methane.
| Parameters | Osmolality8 | Temperature (°C) | Betaine9 | P value$ | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Normal | Hyper | SE∗ | 39.5 | 42 | SE∗ | Control | Low | High | SE∗ | Osmo. | Temp. | Betaine | |
| CH4 production (mL/d) | 87.3 | 49.3 | 18.98 | 66.7 | 69.9 | 1.62 | 50.6c | 60.1b | 94.2a | 13.23 | <0.0001 | 0.2362 | <0.0001 |
| CO2 production (mL/d) | 423.8 | 277.7 | 73.06 | 346.3 | 355.3 | 4.48 | 328.0b | 341.3b | 383.0a | 16.58 | <0.0001 | 0.4607 | 0.0013 |
| Total fermentation gas1 (mL/d) | 550.3 | 365.5 | 92.36 | 450.6 | 465.2 | 7.33 | 418.6b | 438.2b | 516.9a | 30.05 | <0.0001 | 0.3361 | <0.0001 |
| CH4 (% of total gas) | 15.6 | 12.8 | 1.42 | 14.1 | 14.3 | 0.12 | 11.6c | 13.2b | 17.8a | 1.87 | <0.0001 | 0.432 | <0.0001 |
| CO2 (% of total gas) | 77.2 | 76.0 | 0.63 | 76.9 | 76.3 | 0.28 | 77.8a | 77.9a | 74.1b | 1.25 | 0.1106 | 0.474 | <0.0001 |
| Methane formation based on nutrient fermentation (mL/g degraded) | |||||||||||||
| CH4/g OM | 13.5 | 7.9 | 2.82 | 10.7 | 10.7 | 0.00 | 7.8c | 9.5b | 14.8a | 2.11 | <0.0001 | 0.998 | <0.0001 |
| CH4/g DM | 12.2 | 7.1 | 2.56 | 9.7 | 9.7 | 0.01 | 7.0c | 8.6b | 13.4a | 1.91 | <0.0001 | 0.976 | <0.0001 |
| MCR (%GE intake)2 | 1.63 | 0.92 | 0.354 | 1.24 | 1.30 | 0.03 | 0.94c | 1.12b | 1.75a | 0.246 | <0.0001 | 0.234 | <0.0001 |
| Metabolic hydrogen [2H] (mmol/d) | |||||||||||||
| Acetate produced | 59.9 | 50.3 | 4.77 | 53.9 | 56.3 | 1.17 | 52.0b | 55.5a | 57.8a | 1.68 | <0.0001 | 0.058 | 0.0012 |
| Butyrate produced3 | 20.8 | 21.3 | 0.26 | 21.1 | 20.9 | 0.09 | 20.5 | 21.1 | 21.5 | 0.30 | 0.4741 | 0.797 | 0.4898 |
| Caproate produced | 3.76 | 2.99 | 0.386 | 3.02 | 3.74 | 0.36 | 3.60 | 3.37 | 3.17 | 0.125 | 0.1171 | 0.142 | 0.7688 |
| Propionate utilized | 16.4 | 16.7 | 0.16 | 17.6 | 15.5 | 1.05 | 15.7 | 16.8 | 17.0 | 0.42 | 0.6826 | 0.008 | 0.314 |
| Valerate utilized | 3.23 | 2.75 | 0.241 | 2.77 | 3.20 | 0.21 | 3.01 | 3.01 | 2.94 | 0.023 | 0.0072 | 0.016 | 0.9305 |
| Caproate utilized | 7.5 | 6.0 | 0.77 | 6.0 | 7.5 | 0.72 | 7.2 | 6.7 | 6.3 | 0.25 | 0.1166 | 0.143 | 0.7679 |
| CH4 utilized | 13.8 | 7.8 | 3.00 | 10.5 | 11.1 | 0.26 | 8.0c | 9.5b | 14.9a | 2.09 | <0.0001 | 0.235 | <0.0001 |
| Metabolic hydrogen [2H] balance (mmol/d) | |||||||||||||
| Production (pathway 1)4 | 80.6 | 71.6 | 4.5 | 75.0 | 77.2 | 1.07 | 72.4 | 76.6 | 79.3 | 1.9 | <0.0001 | 0.14 | 0.001 |
| Utilization (pathway 1) | 40.9 | 33.2 | 3.85 | 36.9 | 37.2 | 0.14 | 33.9 | 36.1 | 41.2 | 2.16 | <0.0001 | 0.72 | <0.0001 |
| Gain (pathway 1)6 | 39.7 | 38.4 | 0.65 | 38.1 | 40.0 | 0.94 | 38.5 | 40.5 | 38.1 | 0.72 | 0.46 | 0.29 | 0.51 |
| Recovery% (pathway 1)7 | 51.2 | 47.2 | 1.99 | 49.7 | 48.7 | 0.46 | 47.4 | 47.7 | 52.4 | 1.6 | 0.01 | 0.54 | 0.01 |
| Production (pathway 2)5 | 84.4 | 74.6 | 4.89 | 78.0 | 80.9 | 1.43 | 76.0 | 79.9 | 82.4 | 1.86 | <0.0001 | 0.06 | 0.003 |
| Utilization (pathway 2) | 33.4 | 27.2 | 3.08 | 30.9 | 29.7 | 0.57 | 26.7 | 29.4 | 34.8 | 2.40 | <0.0001 | 0.10 | <0.0001 |
| Gain (pathway 2)6 | 51.0 | 47.4 | 1.81 | 47.1 | 51.1 | 2.01 | 49.3 | 50.6 | 47.6 | 0.86 | 0.04 | 0.02 | 0.40 |
| Recovery% (pathway 2)7 | 39.9 | 36.8 | 1.53 | 39.8 | 36.9 | 1.43 | 35.3 | 37.2 | 42.5 | 2.15 | 0.01 | 0.02 | <0.0001 |
1Total fermentation gas = CH4 + CO2 + O2. 2Methane conversion rate. 3Osmolality × temperature interaction. 4Propanyl CoA as intermediate in caproate formation. 5Acetyl CoA as intermediate in caproate formation. 6Production − utilization. 7Utilization/production × 100. 8Normal osmolality ~ 295 mOsmol kg−1; hyperosmolality ~ 420 mOsmol kg−1. 9Betaine levels: control (0), low (51), and high (286) ppm. ∗Standard error. $P value tests the fixed effect of osmolality (n = 36), temperature (n = 36), and betaine addition (n = 24). Significance: P < 0.5.