Alterations in ruminal bacterial populations at induction and recovery from diet-induced milk fat depression in dairy cows
Bibliographic record
Abstract
Ten ruminally cannulated Holstein cows were used in a crossover design that investigated changes in ruminal bacterial populations in response to induction and recovery from diet-induced milk fat depression (MFD). Further, the effect on the ruminal microbiota of the cows with diet-induced milk fat depression inoculated with rumen contents from non-milk fat-depressed donor cows was evaluated. Milk fat depression was induced during the first 10 d of each period by feeding a low-fiber, high-starch, and high-polyunsaturated fatty acid diet (26.1% neutral detergent fiber, 28.1% starch, 5.8% total fatty acids, and 1.9% C18:2), resulting in a 30% decrease in milk fat yield. Induction was followed by a recovery phase, where all cows were switched to a high-fiber, low-starch, and low-polyunsaturated fatty acid diet (31.8% neutral detergent fiber, 23% starch, 4.2% total fatty acids, and 1.2% C18:2) and were allocated to (1) control (no inoculation) or (2) ruminal inoculation with donor cow digesta (8 kg/d for 6 d). Ruminal samples were collected at the end of induction (d 10) and during recovery (d 13, 16, and 28), separated to solid and liquid fractions, extracted for DNA, PCR- amplified for the V1-V2 region of the 16S rRNA gene, and analyzed for bacterial diversity. Results indicated that bacterial communities were different between fractions. In each fraction, differences were significant between the induction (d 10) and recovery (d 13, 16, and 28) periods; however, differences were less apparent with time during the recovery period. The MFD (d 10) was typified by a reduction in the relative sequence abundance of Bacteroidetes and an increase in the relative sequence abundance of Firmicutes and Actinobacteria across both fractions. At the genus level, relative sequence abundance of unclassified Lachnospiraceae, Butyrivibrio, Bulleidia, and Coriobacteriaceae were higher on d 10 and were positively correlated with trans-10,cis-12 CLA and the trans-10 isomer, suggesting their potential role in altered biohydrogenation reactions. A switch to the recovery diet resulted in a sharp increase in the Bacteroidetes lineages and a decrease in Firmicutes members on d 13; however, this shift appears to stabilize by d 28, indicating the restoration process for ruminal bacteria from an altered state is gradual and complex. Inoculation of 10% of rumen contents from non-MFD donor cows to MFD cows revealed this procedure had transient effects on only a few bacterial populations, and such effects disappeared after d 16 following cessation of inoculation. It can be concluded that alterations in milk FA profiles at induction are preceded by microbial alterations in the rumen driven by dietary changes.
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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 | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| 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".