Effects of single-dose ruminal infusions of high or low short-chain fatty acid concentrations and high or low pH on apparent total-tract digestibility and hindgut fermentation of preweaning dairy calves
Bibliographic record
Abstract
Although the importance of pH and short-chain fatty acids (SCFA) on rumen development are well-known, their impact on the small and large intestine are unclear. This study investigated how single-dose ruminal infusions with high or low SCFA concentrations and high or low pH affect calves' productivity, as well as physiological parameters associated with hindgut acidosis at 3 time points in 49 d. Holstein bull calves (n = 32) were individually housed and fed milk replacer (900 g/d) twice daily and calf starter and water ad libitum. At d 10 ± 3 of life, the rumens were fistulated and cannulated. At d 14 of life, calves were grouped by BW and assigned in a 2 × 2 factorial arrangement of treatments: high or low SCFA concentration (285 vs. 10 mM) and high or low pH (6.2 vs. 5.2), creating 4 treatment groups: high SCFA concentration, high pH (HS-HP); high SCFA concentration, low pH (HS-LP); low SCFA concentration, high pH (LS-HP); and low SCFA concentration, low pH (LS-LP). On d 21, 35, 49, feces were sampled to calculate apparent total-tract digestibility, determinate organic acid concentrations (i.e., SCFA, branched-chain fatty acid [BCFA], and lactic acid), and pH. Afterward, the rumen was evacuated and underwent a single-dose infusion for 4 h with 1 of 4 treatment buffers. After completion of rumen infusion on d 49, calves were killed and the tissue weight and length were recorded, along with the digesta pH of the rumen, duodenum, jejunum, ileum, cecum, colon, and rectum. Data were analyzed with main factors as fixed effects and repeated measures for weekly measurements. Treatments did not affect performance parameters such as feed intake, ADG, apparent total-tract digestibility and gut measurements. In the duodenum, jejunum, and ileum, HS-HP had a greater digesta pH than LS-HP, whereas the hindgut digesta pH was only affected by the SCFA concentration. A high SCFA concentration increased the concentration of colonic isovaleric acid and fecal BCFA, whereas only colonic acetic acid and fecal lactic acid concentrations were affected by treatment. Fecal SCFA and BCFA concentrations increased mainly on d 35. In summary, 4 h of physiological buffer infusion in the rumen does not change apparent total-tract digestibility and gut measurements but does affect hindgut fermentation parameters (i.e., organic acid concentrations and digesta pH). In addition, calves can experience increased risks of hindgut acidosis around 35 d of life.
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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) | 0.001 | 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 | 0.001 | 0.001 |
| 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".