Evaluation of n-alkanes as markers for estimation of dry matter intake and digestibility in steers consuming all-forage or forage-concentrate diets
Bibliographic record
Abstract
The study examined the reliability of the alkane-based and chromium (Cr)/in-vitro-based procedures relative to the total fecal collection (TC) technique for estimation of dry matter (DM) intake an d DM digestibility of forage or forage-concentrate diets fed to steers. Eight Holstein steers (208 ± 19.2 kg) were assigned to four dietary treatments in a three-period balanced incomplete block design. The four dietary treatments were: (1) 100% meadow brome grass hay (B); (2) 50% B + 50% alfalfa hay (BA); (3) 50% B + 50% barley grain (BB); and (4) 25% B + 25% alfalfa hay + 50% barley grain (BAB). Two types of hay were chosen to achieve a wide range of alkane intake. Appropriate portions of forages and grain were mixed as a total mixed ration and fed in two equal portions twice daily at 2.5% of body weight, DM basis. Two controlled-release capsules, one containing n-alkanes (C32 and C36) and the other chromic oxide, were placed into the steer's reticulo-rumen by oral administration on day 1 of each 30-d period. Total fecal output was collected twice daily from day 8 to 14 of each period to establish the fecal recovery of Cr and the alkanes, and to determine apparent DM digestibility. A rectal fecal grab sample was also taken every 4 h from day 15 to 16. Fecal recovery of the natural alkanes, C31 and C33, was low, ranging from 59.5 to 77.3%, whereas the range in fecal recovery of the dosed alkanes, C32 and C36, was 83.3 to 95.5%, and of Cr was 82.7 to 95.8% across the diets. The estimated DM intake was similar across all diets using the C31/C32 and C33/C32 alkane ratios; however, estimated DM intakes using the alkane method were significantly (P < 0.05) lower compared to TC and Cr/in vitro methods for the BB diet. Addition of barley to the forage diets resulted in a higher DM digestibility for BB and BAB diets by all methods. The estimated DM digestibility using the C31/C32 ratio was lower compared to the TC method for diet B, BA and BB, whereas the estimated DM digestibility using C33/C32 was lower only for the BB diet. Sampling every 4 h resulted in a significantly higher ratio of C 31 to C32 in feces compared to samples collected by the TC method. Rectal grab sampling did not change (P > 0.05) the estimated DM intake using either combination of alkane ratio. Key words: Alkanes, chromium oxide, dry matter intake, dry matter digestibility, steer
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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) | 0.000 | 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) | 0.000 | 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".