Table 3.
Effect of slow-release urea supplementation on fermentation pH and characteristics in Rusitec
| Item | Treatmenta | Pb | ||||||
|---|---|---|---|---|---|---|---|---|
| Control | U28 | U56 | MU35 | SEM | L | Q | C vs. MU35 | |
| pH | 6.81 | 6.80 | 6.80 | 6.77 | 0.01 | 0.25 | 0.47 | 0.03 |
| NH3-N, mmol/L | 7.70 | 9.31 | 10.25 | 8.92 | 0.37 | 0.01 | 0.39 | 0.03 |
| Total VFA, mmol/L | 78.5 | 80.2 | 79.3 | 85.7 | 2.86 | 0.21 | 0.65 | 0.08 |
| % of total VFA | ||||||||
| Acetate (A) | 46.1 | 45.6 | 46.4 | 47.2 | 0.57 | 0.57 | 0.16 | 0.16 |
| Propionate (P) | 26.9 | 25.7 | 26.0 | 26.5 | 0.21 | 0.01 | 0.01 | 0.16 |
| Butyrate | 14.9 | 15.5 | 15.2 | 14.2 | 0.24 | 0.38 | 0.13 | 0.04 |
| BCVFA3 | 2.8 | 3.2 | 2.9 | 3.2 | 0.09 | 0.87 | 0.01 | 0.02 |
| Valerate | 7.8 | 8.4 | 7.9 | 7.4 | 0.25 | 0.63 | 0.03 | 0.22 |
| Caproate | 1.3 | 1.6 | 1.5 | 1.4 | 0.05 | 0.02 | 0.01 | 0.08 |
| A:P | 1.69 | 1.77 | 1.78 | 1.77 | 0.03 | 0.01 | 0.24 | 0.02 |
| Total VFA, mmol/d | 50.5 | 53.1 | 52.0 | 55.9 | 2.05 | 0.13 | 0.18 | 0.06 |
| Protozoa, × 104/mL | 2.4 | 2.9 | 2.8 | 2.8 | 0.24 | 0.91 | 0.17 | 0.24 |
aControl (no SRU), U28 = control plus 0.28% SRU, U56 = control plus 0.56% SRU, and MU35 = control diet was modified by partially replacing soybean protein with 0.35% SRU (DM basis);
bL, Q = linear and quadratic effects of SRU (control, U28 and U56); C vs. MU35 = Contrast between Control and MU35
cBCVFA = Branched-chain volatile fatty acids (isobutyrate + isovalerate)