Table 6.
Gas production parameters and fermentation parameters after 8 and 24 h of in vitro fermentation of diets containing increased amounts of tomato pomace incubated in batch cultures of mixed rumen microorganisms 1.
| Item and Incubation Time | Control | TP6 | TP12 | TP18 | SEM 1 | p-Value | |
|---|---|---|---|---|---|---|---|
| Lineal | Quadratic | ||||||
| Gas production parameters 2 | |||||||
| PGP (mL/g dry matter (DM)) | 336 | 334 | 326 | 334 | 3.67 | 0.453 | 0.229 |
| c (%/h) | 4.17 a | 4.62 b | 4.73 b | 4.58 b | 0.121 | 0.016 | 0.015 |
| lag (h) | 1.63 | 1.42 | 2.03 | 1.90 | 0.30 | 0.325 | 0.894 |
| AGPR mL/h | 9.16 | 10.1 | 9.74 | 9.76 | 0.37 | 0.416 | 0.236 |
| DMED (%) | 33.4 | 35.4 | 34.1 | 33.3 | 0.73 | 0.983 | 0.175 |
| Fermentation parameters at 8 h incubation 3 | |||||||
| Total VFA (mmol/g DM) | 3.47 | 3.44 | 3.52 | 3.62 | 0.075 | 0.161 | 0.430 |
| Molar proportions (mol/100 mol) | |||||||
| Acetate (Ac) | 57.7 a | 58.3 b | 58.1 b | 58.2 b | 0.12 | 0.059 | 0.038 |
| Propionate (Pr) | 23.9 a | 23.9 a | 24.4 b | 24.4 b | 0.13 | 0.007 | 0.971 |
| Butyrate | 15.0 b | 14.6 a | 14.4 a | 14.4 a | 0.09 | 0.009 | 0.053 |
| Minor VFA | 3.37 c | 3.18 b | 3.08 a | 3.04 a | 0.043 | 0.002 | 0.095 |
| Acetate/propionate (mol/mol) | 2.46 ac | 2.48 ac | 2.42 ab | 2.42 a | 0.022 | 0.039 | 0.405 |
| NH3-N (mg/L) | 185 b | 182 ab | 181 ab | 178 a | 2.1 | 0.049 | 0.815 |
| CH4 (mL/g DM) | 18.5 | 18.0 | 18.0 | 18.4 | 0.36 | 0.901 | 0.296 |
| CH4/VFA (mL/mmol) | 5.34 b | 5.24 ab | 5.16 ab | 5.09 a | 0.082 | 0.047 | 0.836 |
| FOM (mg/g) | 332 | 328 | 334 | 345 | 7.2 | 0.178 | 0.325 |
| Fermentation parameters at 24 h incubation 3 | |||||||
| pH | 6.71 c | 6.71 c | 6.67 b | 6.63 a | 0.011 | 0.003 | 0.222 |
| Total VFA (mmol/g DM) | 6.82 a | 6.84 a | 6.91 ab | 6.99 b | 0.050 | 0.029 | 0.610 |
| Molar proportions (mol/100 mol) | |||||||
| Acetate (Ac) | 58.6 | 58.8 | 58.4 | 58.5 | 0.07 | 0.150 | 0.569 |
| Propionate (Pr) | 19.4 a | 19.6 a | 20.1 b | 20.1 b | 0.14 | 0.002 | 0.594 |
| Butyrate | 17.5 | 17.4 | 17.5 | 17.5 | 0.10 | 0.705 | 0.576 |
| Minor VFA | 4.40 b | 4.14 b | 4.10 b | 3.96 a | 0.071 | 0.002 | 0.421 |
| Ac/Pr (mol/mol) | 3.08 b | 3.05 b | 2.96 a | 2.96 a | 0.022 | 0.007 | 0.465 |
| NH3-N (mg/L) | 284 b | 270 b | 271 b | 269 a | 4.8 | 0.066 | 0.215 |
| CH4 (mL/g dry matter) | 43.1 | 41.8 | 41.0 | 42.4 | 1.38 | 0.658 | 0.371 |
| CH4/VFA (mL/mmol) | 6.33 | 6.11 | 5.93 | 6.05 | 0.213 | 0.312 | 0.450 |
| FOM (mg/g) | 660 a | 661 a | 668 ab | 680 b | 4.3 | 0.007 | 0.293 |
abc Within each parameter, mean values with different superscripts differ (p < 0.05). 1 Control, TP6, TP12, and TP18 diets contained 0, 60, 120, and 180 g of tomato pomace per kg, respectively (fresh matter basis). 2 PGP: Asymptotic gas production; c: Fractional rate of gas production; lag: Time before starting gas production; AGPR: Average gas production rate; DMED: Dry matter effective degradability calculated for a rumen particulate outflow of 4%/h. 3 VFA: Volatile fatty acids; minor VFA were calculated as the sum of isobutyrate, isovalerate, and valerate; FOM: Fermented organic matter calculated from acetate, propionate, and butyrate production as described by Demeyer [25].