Differing effects of 2 active dried yeast (Saccharomyces cerevisiae) strains on ruminal acidosis and methane production in nonlactating dairy cows
Bibliographic record
Abstract
Fifteen ruminally cannulated, nonlactating Holstein cows were used to measure the effects of 2 strains of Saccharomyces cerevisiae, fed as active dried yeasts, on ruminal pH and fermentation and enteric methane (CH(4)) emissions. Nonlactating cows were blocked by total duration (h) that their ruminal pH was below 5.8 during a 6-d pre-experimental period. Within each block, cows were randomly assigned to control (no yeast), yeast strain 1 (Levucell SC), or yeast strain 2 (a novel strain selected for enhanced in vitro fiber degradation), with both strains (Lallemand Animal Nutrition, Montréal, QC, Canada) providing 1 × 10(10) cfu/head per day. Cows were fed once daily a total mixed ration consisting of a 50:50 forage to concentrate ratio (dry matter basis). The yeast strains were dosed via the rumen cannula daily at the time of feeding. During the 35-d experiment, ruminal pH was measured continuously for 7 d (d 22 to 28) by using an indwelling system, and CH(4) gas was measured for 4 d (d 32 to 35) using the sulfur hexafluoride tracer gas technique (with halters and yokes). Rumen contents were sampled on 2 d (d 22 and 26) at 0, 3, and 6h after feeding. Dry matter intake, body weight, and apparent total-tract digestibility of nutrients were not affected by yeast feeding. Strain 2 decreased the average daily minimum (5.35 vs. 5.65 or 5.66), mean (5.98 vs. 6.24 or 6.34), and maximum ruminal pH (6.71 vs. 6.86 or 6.86), and prolonged the time that ruminal pH was below 5.8 (7.5 vs. 3.3 or 1.0 h/d) compared with the control or strain 1, respectively. The molar percentage of acetate was lower and that of propionate was greater in the ruminal fluid of cows receiving strain 2 compared with cows receiving no yeast or strain 1. Enteric CH(4) production adjusted for intake of dry matter or gross energy, however, did not differ between either yeast strain compared with the control but it tended to be reduced by 10% when strain 2 was compared with strain 1. The study shows that different strains of S. cerevisiae fed as active dried yeasts vary in their ability to modify the rumen fermentative pattern in nonlactating dairy cows. Because strain 2 tended (when compared with strain 1) to lower CH(4) emissions but increase the risk of acidosis, it may be prudent to further evaluate this strain in cattle fed high-forage diets, for which the risk of acidosis is low but CH(4) emissions are high.
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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 | 0.000 | 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".