Proteolytic activity in ruminal fluid from cattle fed two levels of barley grain: a comparison of three methods of determination
Bibliographic record
Abstract
Abstract The effects of proportion of concentrate in the ruminant diet and the effects of freezing ruminal content prior to assay on proteolytic activity in ruminal inoculum were evaluated using three analytical techniques. A novel approach for determining proteolytic activity (PA) of ruminal fluid utilising 15N‐labelled casein was compared with two published procedures. In a crossover experiment, four heifers were fed two isonitrogenous diets containing (dry matter basis) 50% barley silage, 45% rolled barley grain and 4% soybean meal (medium‐grain diet, MG) or 8% barley silage, 89% rolled barley grain and 2% soybean meal (high‐grain diet, HG). Ruminal fluid was analysed either fresh or after having been frozen at −40 °C for 45 days. Substrates utilised in measuring PA included 15N‐labelled casein (produced by infusing (15NH)2SO4 into the rumen of a lactating dairy cow), 14C‐labelled casein and azocasein. Incubations were conducted in 0.2 M phosphate buffer (pH 6.8) for 20 min at 39 °C. In the 15N‐casein incubations, PA was estimated as (i) N soluble in 5% trichloroacetic acid (TCASN), (ii) N soluble in 5% TCA corrected for microbial N uptake (TCAMICR) and (iii) N depleted from the soluble protein N pool (SPR). In the 14C‐casein incubations, PA was measured as TCA‐soluble radioactivity; in the azocasein method it was measured as dye released during incubation. Across treatments the highest (P < 0.001) proteolytic activity was measured by the SPR method, followed by TCAMICR, TCASN and 14C‐casein. The lowest activity was recorded using the azocasein method. Within the 15N‐ and 14C‐casein methods, PA in previously frozen ruminal fluid was higher (P < 0.05) with the HG diet than with the MG diet, and higher (P < 0.05) in previously frozen fluid than in inoculum processed fresh. This study demonstrates that increasing the proportion of grain in the diets of cattle and freezing the ruminal inoculum both increase proteolytic activity measured in ruminal fluid. The proposed 15N‐casein method yielded higher proteolytic activity values than the 14C‐casein method. Copyright © 2002 Society of Chemical Industry. Contributions of A N Hristov, T A McAllister and Z Xu. © Minister of Public Works and Government Services, Canada 2002.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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 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".