Histidine optimal supply in dairy cows through determination of a threshold efficiency
Bibliographic record
Abstract
Two His deletion studies were conducted to examine the mechanisms used by dairy cows to support milk true protein yield (MTPY) when His supply is altered. The potential mechanisms involved in how the efficiency of utilization of His varied included reduced catabolism, more efficient mammary usage, and use of His labile pools. For the first study, 5 multicatheterized cows were used in a 4 × 4 Latin square plus 1 cow with 14-d periods. Treatments were abomasal infusion of increasing doses of His (0, 7.6, 15.2, and 20.8 g/d) in addition to a mixture of AA (595 g/d; casein profile excluding His). Cows were fed the same protein-deficient diet throughout the study. The MTPY increased linearly with a quadratic tendency with increasing doses of His. Muscle concentrations of carnosine, a His-based dipeptide, tended to increase in a quadratic manner with increasing His supply, suggesting that the 0- and 7.6-g doses were insufficient to cover His requirement. Liver catabolism of His decreased as His supply decreased. Mammary fractional removal of His was considerably greater at low His supply, but the ratio of His mammary net uptake to milk output was not affected by the rate of His infusion, averaging 1.02. The mechanisms to face a reduced His supply included reduced His hepatic catabolism, more efficient His mammary use of lowered arterial supply, and, to a lesser extent, use of His labile pools. Two independent estimates of His efficiency were calculated, one based on the sum of exported proteins (measured MTPY plus estimated metabolic fecal protein and scurf; i.e., the anabolic component, Eff MTPY ) and the other based on liver removal (i.e., the catabolic component). These 2 estimates followed the same pattern of response to His supply, decreasing with increasing His supply. The Eff MTPY at which MTPY peaked was 0.785. For the second study, 6 cows were used in a 6 × 6 Latin square with 7-d periods. Two greater doses of His (30.4 and 38.0 g/d) were added; otherwise, the nutritional design was similar to the first study. In this second study, the indicator AA oxidation technique was used instead of the multiorgan approach, with labeled Leu as the indicator of His utilization. The MTPY peaked and Leu oxidation reached the nadir at an average Eff MTPY of 0.763. Combined across both studies, the data indicate that optimal usage of His would occur at a threshold Eff MTPY of 0.77. The agreement between experimental approaches across both studies indicates that the biological optimal supply of His expressed in grams per day could be calculated as the sum of exported proteins divided by this Eff MTPY plus estimated endogenous urinary excretion.
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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 | 0.001 |
| 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) | 0.001 | 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".