Short communication: Blood metabolites, body reserves, and feed efficiency of high-producing dairy cows that varied in ruminal pH when fed a high-concentrate diet
Bibliographic record
Abstract
Recent studies report considerable variation in ruminal pH for lactating dairy cows even when fed the same diet. We hypothesized that blood metabolites would be indicators of low ruminal pH, and hence could be used as predictors to help manage this variability. The objective of the study was to determine whether blood metabolite concentrations, body reserves, and feed efficiency were associated with ruminal pH in high-producing dairy cows fed a high-concentrate diet. Seventy-eight individually fed lactating dairy cows (days in milk=103 ± 27; body weight=638 ± 77 kg at the start; mean ± SD) were fed a diet consisting of 35% forage and 65% concentrate (dry matter basis). Cows were adapted for 14 d and then were sampled for 10 d. Ruminal pH was measured by rumenocentesis for all cows at the end of the study 4 h after feeding, and reticular pH was measured on a subsample of 14 cows via indwelling sensors for 5 consecutive days. Cows were classified according to rumenocentesis pH as high (pH ≥ 6.0; n=26), medium (5.8 ≤ pH < 6; n=21), and low (pH < 5.8; n=31). Cows were also classified according to reticular pH as high if pH <5.8 persisted <330 min/d (an average of 78 min/d; n=5) or low if duration of pH <5.8 was ≥330 min/d (an average of 920 min/d; n=9). The classification based on rumenocentesis pH revealed that serum activity of aspartate aminotransferase (AST) was greater in cows with low ruminal pH (70.7 U/L) than cows with high (56.6 U/L) and medium (59.9 U/L) ruminal pH. Also, the blood urea nitrogen concentration was greater in cows with low ruminal pH (13.6 mg/dL) than cows with medium (12.2 mg/dL) and high (12.5 mg/dL) ruminal pH. Blood albumin concentration was greater for cows with low ruminal pH than for cows with medium and high ruminal pH. The classification based on reticular pH also resulted in a trend of greater AST activity and greater blood urea nitrogen concentration in the blood of cows with low pH. Regression analysis showed high serum concentration of AST was associated with high valerate concentration in ruminal fluid (R 2 = 0.14), low rumenocentesis pH (R 2 = 0.10), and low milk fat percentage (R 2 = 0.06). Glucose, triglyceride, cholesterol, globulin, alkaline phosphates, and serum amyloid A did not differ among the different ruminal pH classes. Low pH cows (reticular and ruminal) had less backfat thickness measured via ultrasound, and cows with low ruminal pH tended to have greater milk:feed ratio. Results indicated that cows that differ in ruminal pH also had different concentrations of blood metabolites and backfat thickness, and AST activity in blood may be a plausible indicator of ruminal pH in dairy cows. Further studies on the applicability of AST in blood as a biomarker for detecting low ruminal pH in dairy cows are warranted.
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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".