Abstract
Key words
Abbreviation key:
A:P (acetate-to-propionate), F:C (forage-to-concentrate ratio), HF (high forage (70 forage:30 concentrate)), LF (low forage (30 forage:70 concentrate)), MF (medium forage (50 forage:50 concentrate))Introduction
Materials and Methods
Incubation Conditions
Dietary Treatments and Dilution Rates
Sampling and Analyses
Ten microliters of headspace gas samples from the fermentor was drawn into a gas-tight syringe (Hamilton Co., Reno, NV) and analyzed for CH4 by GLC (model CP-3800; Varian) using a stainless steel column packed with Molsieve 5A 45/60 mesh (Supelco Inc.). The pH of the ruminal cultures was monitored continuously and recorded when samples for CH4 were taken.
Energy contents of acetate, propionate, butyrate, valerate, isobutyrate, and isovalerate were used to estimate digestible energy. Similarly, energy content of CH4 was used to estimate contribution of energy in CH4 to total digestible energy. In addition to direct measurement of CH4, the production of fermentation gases, CO2 and CH4, and the associated production of H2O, was calculated using the equation outlined by
Experimental Design and Statistical Analyses
where
Results
VFA | DR, %/h | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
3.2 | 6.3 | 12.5 | Significance of effect | ||||||||||
HF | MF | LF | HF | MF | LF | HF | MF | LF | SE | DR | F:C | DR × F:C | |
Total, mM | 97.7 | 100.4 | 104.0 | 56.9 | 63.2 | 59.5 | 27.3 | 25.7 | 29.6 | 2.69 | 0.01 | NS4 | NS |
Individual, mol/100 mol | |||||||||||||
Acetate (A) | 53.0 | 52.7 | 50.0 | 54.9 | 48.6 | 44.6 | 60.6 | 54.4 | 49.9 | 2.07 | NS | 0.01 | NS |
Propionate (P) | 28.9 | 29.8 | 29.4 | 26.1 | 31.2 | 35.5 | 18.7 | 25.2 | 22.4 | 1.64 | 0.07 | 0.03 | NS |
Butyrate | 12.0 | 11.5 | 14.1 | 12.1 | 12.5 | 11.8 | 15.5 | 11.9 | 20.8 | 0.38 | 0.02 | 0.01 | 0.01 |
Valerate | 3.9 | 5.0 | 5.5 | 2.9 | 3.1 | 3.7 | 1.8 | 1.7 | 2.4 | 0.26 | 0.01 | 0.01 | NS |
Isobutyrate | 0.3 | 0.3 | 0.3 | 0.9 | 0.9 | 0.8 | 0.7 | 0.4 | 1.0 | 0.13 | 0.01 | NS | NS |
Isovalerate | 2.0 | 0.9 | 0.9 | 3.2 | 3.9 | 3.8 | 3.0 | 6.5 | 3.7 | 0.31 | 0.01 | 0.01 | 0.01 |
A:P ratio | 1.9 | 1.8 | 1.8 | 2.2 | 1.6 | 1.3 | 3.3 | 2.3 | 2.3 | 0.20 | 0.01 | 0.01 | NS |
Total, mmol/d | 51.8 | 53.2 | 55.1 | 59.8 | 66.3 | 62.5 | 57.3 | 54.0 | 62.3 | 3.19 | NS | NS | NS |
Individual, mmol/d | |||||||||||||
Acetate | 27.5 | 27.9 | 27.4 | 32.9 | 31.9 | 27.8 | 34.7 | 30.0 | 31.5 | 2.11 | NS | NS | NS |
Propionate | 14.9 | 16.0 | 16.4 | 15.6 | 20.9 | 22.2 | 10.7 | 13.3 | 13.8 | 1.21 | NS | 0.02 | NS |
Butyrate | 6.2 | 6.1 | 7.7 | 7.2 | 8.4 | 7.4 | 8.8 | 6.3 | 12.8 | 0.69 | NS | 0.01 | 0.02 |
Valerate | 2.0 | 2.7 | 3.0 | 1.7 | 2.1 | 2.3 | 1.0 | 0.9 | 1.5 | 0.21 | 0.01 | 0.02 | NS |
Isobutyrate | 0.2 | 0.2 | 0.2 | 0.5 | 0.6 | 0.5 | 0.4 | 0.3 | 0.6 | 0.05 | NS | NS | 0.03 |
Isovalerate | 1.1 | 0.5 | 0.5 | 1.9 | 2.6 | 2.4 | 1.7 | 3.4 | 2.3 | 0.13 | 0.01 | 0.01 | 0.01 |
Item | DR, %/h | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
3.2 | 6.3 | 12.5 | Significance of effect | ||||||||||
HF | MF | LF | HF | MF | LF | HF | MF | LF | SE | DR | F:C | DR × F:C | |
pH | 5.3 | 5.0 | 5.0 | 5.7 | 5.5 | 5.6 | 6.7 | 6.3 | 6.3 | 0.20 | 0.08 | NS | NS |
NH3-N, mg/dl | 15.6 | 14.7 | 12.1 | 27.3 | 31.1 | 25.5 | 18.2 | 19.5 | 21.9 | 1.54 | 0.01 | NS | NS |
NH3-N, g/d | 0.09 | 0.08 | 0.06 | 0.29 | 0.33 | 0.27 | 0.38 | 0.41 | 0.46 | 0.016 | 0.01 | NS | 0.07 |
Gas estimated, mmol/d | 88.5 | 89.4 | 104.2 | 102.8 | 109.7 | 99.9 | 106.5 | 92.1 | 115.2 | 7.21 | NS | NS | NS |
CH4 estimated, mmol/d | 13.1 | 13.1 | 13.4 | 16.1 | 14.9 | 12.1 | 19.1 | 14.8 | 18.7 | 1.39 | NS | NS | NS |
CH4 measured | |||||||||||||
mmol/d | 9.6 | 6.1 | 4.2 | 25.5 | 19.6 | 11.2 | 29.1 | 20.1 | 22.0 | 1.15 | 0.01 | 0.01 | 0.02 |
mmol/g DM fed | 0.8 | 0.5 | 0.3 | 2.0 | 1.5 | 0.9 | 2.3 | 1.6 | 1.7 | 0.10 | 0.01 | 0.01 | 0.04 |
Item | DR, %/h | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
3.2 | 6.3 | 12.5 | Significance of effect | ||||||||||
HF | MF | LF | HF | MF | LF | HF | MF | LF | SE | DR | F:C | DR × F:C | |
DM fed, g/d | 12.8 | 12.9 | 13.0 | 12.8 | 12.9 | 13.0 | 12.8 | 12.9 | 13.0 | ||||
Substrate used, g/d | |||||||||||||
For VFA | 3.3 | 3.4 | 4.2 | 3.8 | 4.2 | 4.0 | 3.7 | 3.3 | 4.0 | 0.29 | NS | NS | NS |
For gas | 1.9 | 1.8 | 2.0 | 2.2 | 2.3 | 2.0 | 2.5 | 2.0 | 2.7 | 0.16 | 0.02 | NS | NS |
For microbial biomass | 1.0 | 1.0 | 1.2 | 1.7 | 1.9 | 1.8 | 2.5 | 2.2 | 2.7 | 0.13 | 0.01 | NS | NS |
Total | 6.1 | 6.2 | 7.5 | 7.7 | 8.4 | 7.7 | 8.6 | 7.6 | 9.4 | 0.56 | 0.03 | NS | NS |
Fermentability, % | 48.0 | 48.4 | 57.3 | 60.2 | 65.0 | 59.6 | 66.9 | 58.6 | 72.3 | 4.30 | 0.03 | NS | NS |
Microbial synthesis | |||||||||||||
g/d | 0.79 | 0.81 | 0.98 | 1.39 | 1.54 | 1.45 | 1.96 | 1.78 | 2.16 | 0.104 | 0.01 | NS | NS |
g DM/kg DM fermented | 132.7 | 133.5 | 136.4 | 189.2 | 193.0 | 196.6 | 243.4 | 250.8 | 243.9 | 1.41 | 0.01 | 0.02 | 0.05 |
Item | DR, %/h | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
3.2 | 6.3 | 12.5 | Significance of effect | ||||||||||
HF | MF | LF | HF | MF | LF | HF | MF | LF | SE | DR | F:C | DR × F:C | |
DE fed, kcal/d | 38.1 | 41.2 | 44.4 | 38.1 | 41.2 | 44.4 | 38.1 | 41.2 | 44.4 | ||||
VFA | |||||||||||||
kcal/d | 16.6 | 17.1 | 18.3 | 19.2 | 22.2 | 21.3 | 17.9 | 17.5 | 21.2 | 1.04 | NS | 0.08 | NS |
% of DE | 43.6 | 41.6 | 41.1 | 50.3 | 53.9 | 47.8 | 46.9 | 42.5 | 47.8 | 2.47 | NS | NS | NS |
CH4 | |||||||||||||
kcal/d | 2.0 | 1.3 | 0.9 | 5.4 | 4.1 | 2.4 | 6.2 | 4.2 | 4.7 | 0.23 | 0.01 | 0.01 | 0.01 |
% of DE | 5.3 | 3.2 | 2.0 | 14.1 | 10.0 | 5.3 | 16.1 | 10.3 | 10.5 | 0.56 | 0.01 | 0.01 | 0.01 |
Discussion
Conclusions
Acknowledgments
Supplementary data
- Interpretive summary
References
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