Choline metabolism in high-producing dairy cows: Metabolic and nutritional basis
Bibliographic record
Abstract
Choline, the beta-hydroxyethyltrimethylammonium ion, is a strong base containing a trimethylated quaternary nitrogen. Choline occurs widely in biological materials as the compound itself, as acetylcholine and as various phospholipids. In feed ingredients and crude unprocessed fat sources, most choline is present as phosphatidylcholine (lecithin). Although soybean, soybean meal, rapeseed meal, fish meal and dried yeast are relatively rich sources of choline, the bioavailability of choline in these feedstuffs is only moderate. In dairy ruminants, choline is extensively degraded in the rumen. For this reason, dietary choline contributes insignificantly to the choline body pool, and methyl group metabolism is generally conservative with a relatively low rate of methyl catabolism and an elevated rate of de novo synthesis of methyl groups via the tetrahydrofolate system. Gluconeogenic precursors are the primary sources of the new methyl groups. Depending on energy balance and physiological state, such precursors can be deficient in ruminants. In situations of glucose imbalance, for example at the onset of lactation in the dairy cow, choline may become a limiting nutrient for milk production, owing to the extra demand for methyl groups. Furthermore, choline is a lipotropic substance and it may optimize the balance between fat retained and fat metabolized by the liver, thereby improving lipid metabolism in general. The data reviewed in this paper are consistent with these assumptions and support the fact that choline supplementation for dairy cows, in a form protected from ruminal degradation, may improve methyl group metabolism and the status of other nutrients, including vitamin E. Key words: Choline, methyl groups, methionine, dairy cows, rumen-protected choline
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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 | 0.001 | 0.001 |
| 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".