Validation of the sulphur hexafluoride (SF<sub>6</sub>) tracer gas technique for measurement of methane and carbon dioxide production by cattle
Bibliographic record
Abstract
Methane (CH 4 ) and carbon dioxide (CO 2 ) production from six crossbred yearling beef heifers (400 ± 13.0 kg) were measured, using the sulphur hexafluoride (SF 6 ) tracer gas technique (Tracer) and open-circuit hood calorimetry (Cal) to validate the former in estimating rumen CH 4 and CO 2 production in the field. Animals were individually fed a diet consisting of 50% barley concentrate and 50% alfalfa cubes at 1.3 &times ;maintenance requirements daily. Hifers were divided into two groups for individual animal 24- h gas measurements by each method. Each group of heifers was rotated between the Cal and Tracer techniques for 6 consecutive days in an incomplete block design. Methane production ranged from 108 to 145 L d -1 (mean 130 ± 4.0 L d -1 ) using the Cal technique, and 90 to 167 L d -1 (mean 137 ± 4.0 L d -1 ) using the Tracer technique. The mean CH 4 production (L d -1 ) was not different (P = 0.24) between the two methods. Carbon dioxide production with the Tracer technique was 20% higher than CO 2 production with the Cal technique (P < 0.01). The range of CO 2 production was 1574 to 2049 L d -1 (mean 1892 ± 74.0 L d -1 ) by Cal, and 1541 to 3330 L d -1 (mean 2353 ± 74.0 L d -1 ) by Tracer. Day-to-day variation in CH 4 production was not different within each method (P > 0.05); however, animal-to-animal variation (11.7%) was significant for the Tracer technique (P = 0.04), but not for the Cal technique (P = 0.53). Comparison of the equality of variance between the two methods showed that there were no differences in variations (P > 0.05) between Cal and Tracer for CH 4 production. On the other hand, variations in CO 2 production were not equal (P > 0.05) between methods. Day-to-day variation in CO 2 production was significant using Cal, but not Tracer (P > 0.05). Animal-to-animal variation in CO 2 production was 1.6 and 11.8% by Cal and Tracer techniques, respectively. It can be concluded that the SF 6 tracer technique accurately estimated rumen CH 4 production, but CO 2 production was 20% higher. The study suggests that for CH 4 measurements using the SF 6 tracer technique, more animal numbers are needed than for Cal to reduce animal-to-animal variation. Key words: Methane, carbon dioxide, SF 6 tracer technique, validation, cattle
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".