Table 1.
Feed intake, performance, methane production, rumen fermentation parameters, and microbial population sizes in cattle in different age groups.
| Item | Means ± SE |
P-value | ||
|---|---|---|---|---|
| S1 (n = 6) | S2 (n = 7) | S3 (n = 7) | ||
| Performance and methane production | ||||
| Body weight (kg) | 321.33 ± 14.97a | 663.14 ± 13.51b | 686.43 ± 8.20b | 0.001 |
| DMI (kg/day) | 6.37 ± 0.09a | 16.15 ± 0.09c | 15.25 ± 0.12b | 0.010 |
| CH4 (g/day/head) | 191.93 ± 11.44a | 379.02 ± 8.88c | 313.73 ± 9.95b | 0.001 |
| CH4 (g/kg DMI) | 30.13 ± 1.80b | 23.47 ± 0.59a | 20.57 ± 0.65a | 0.001 |
| CH4 (g/100 kg body weight) | 60.34 ± 4.34b | 57.33 ± 1.96b | 45.66 ± 1.06a | 0.002 |
| Rumen fermentation | ||||
| Ammonia–N (mg/dL) | 28.91 ± 1.95b | 27.94 ± 1.82b | 21.19 ± 2.24a | 0.029 |
| Acetate (mmol/L) | 55.93 ± 7.56 | 65.69 ± 10.79 | 80.09 ± 7.11 | 0.183 |
| Propionate (mmol/L) | 14.31 ± 1.20a | 19.00 ± 2.25a | 29.47 ± 3.03b | 0.001 |
| Butyrate (mmol/L) | 8.51 ± 1.74a | 10.38 ± 2.10ab | 14.08 ± 1.11b | 0.094 |
| Total VFA (mmol/L) | 78.75 ± 10.40a | 95.07 ± 16.16ab | 123.62 ± 11.17b | 0.054 |
| A:P ratio | 3.95 ± 0.52b | 3.40 ± 0.22ab | 2.79 ± 0.20a | 0.071 |
| Microbial population size | ||||
| Total methanogen (log copies/mL) | 9.61 ± 0.14a | 9.73 ± 0.08ab | 9.92 ± 0.08b | 0.124 |
| Total bacteria (log copies/mL) | 11.59 ± 0.11 | 11.78 ± 0.09 | 11.76 ± 0.13 | 0.446 |
| Methanogen:bacteria proportion (%) | 1.13 ± 0.19 | 1.07 ± 0.26 | 1.55 ± 0.27 | 0.340 |
Within a row, different superscript letters indicate p < 0.05, and means without superscript letters indicate p > 0.05. A:P = acetate:propionate ratio. S1 indicates heifers (9–10 months); S2 indicates young adults (45–65 months); S3 indicates older adults (96–120 months).