0474 Comparison of digestion and particle-associated bacteria after in situ incubation of different barley varieties in the rumen of cattle
Bibliographic record
Abstract
The chemical composition of barley grain, including the structure of starch, can vary among barley varieties and result in different digestion efficiencies. It is not known if compositional differences in barley can affect the particle-associated bacteria (PAB) involved in digestion. Therefore, the objective of this study was to characterize the in situ rumen digestion and PAB of four barley grain varieties. Three ruminally-cannulated cattle were fed a diet of 60% barley silage, 37% barley grain and 3% supplement. Four different barley varieties (Fibar, Xena, McGwire and Hilose) and corn as a control were included in the experiment. Ground grains (3 g) were placed in nylon bags and incubated in the rumen of cattle for 0, 2, 4, 12, 24, and 48 h. At each time point, triplicate bags were removed from each animal and analyzed for dry matter (DM), starch and crude protein (CP) disappearance. A second set of bags (n = 3) containing 5 g of each grain were incubated for 2, 4, and 12 h and DNA was extracted to characterize PAB via 16S rRNA gene sequencing. McGwire had the highest effective degradability (ED) of DM (P < 0.01), followed by Xena, Fibar, Hilose, and corn, respectively. The ED of starch was highest (P < 0.01) for Xena, followed by McGwire, Fibar, Hilose, and corn, while CP disappearance was not affected by grain type. Overall, 15 phyla were identified after analysis of 16S rRNA genes. Barley variety did not affect the relative abundance of phyla however they did differ with incubation time. Firmicutes (19.2%), Bacteroidetes (18.27%) and Proteobacteria (8.89%) were the dominant phyla after 2 h of incubation. By 12 h, Bacteroidetes decreased to a relative abundance of 4.3%. In contrast, Firmicutes increased in abundance over time, accounting for 45.9 and 82.1% of PAB after 4 and 12 h of incubation, respectively. Principal Coordinate Analysis showed that bacterial populations clearly grouped according to incubation time. At the family level, Lactobacillaceae increased over time, with a relative abundance of 0.76, 6.49, and 76.3% at 2, 4, and 12 h, respectively, reflecting an increasing presence of lactic-acid producing bacteria. This study found that the diversity of PAB on barley grain was not affected by barley variety, despite there being differences in digestion kinetics. However, time affected PAB, illustrating that the bacterial biofilm involved in the digestion of grains clearly undergoes compositional shifts during ruminal digestion.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| 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 | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".