Effects of Forage Particle Size and Grain Fermentability in Midlactation Cows. II. Ruminal pH and Chewing Activity
Bibliographic record
Abstract
Our study investigated the effects of, and interactions between, level of dietary ruminally fermentable carbohydrate (RFC) and forage particle size on rumen pH and chewing activity for dairy cows fed one level of dietary NDF. Also, correlations between intake, production, chewing, and ruminal pH parameters were investigated. Eight cows (61 days in milk) were assigned to four treatments in a double 4 x 4 Latin square. Treatments were arranged in a 2 x 2 factorial design; finely chopped alfalfa silage (FS) and coarse alfalfa silage (CS) were combined with concentrates based on either dry, cracked-shelled corn (DC; low RFC) or ground, high-moisture corn (HMC; high RFC). Diets were fed ad libitum as a total mixed rations with a concentrate:forage ratio of 60:40. Diets averaged 18.7% crude protein, 24.0% neutral detergent fiber, 18.3% , acid detergent fiber and 27.4% starch on a DM basis. Mean particle size of the four diets were 6.3, 2.8, 6.0, and 3.0 mm for DCCS, DCFS, HMCCS, and HMCFS, respectively. Decreasing forage particle size decreased ruminal pH from 6.02 to 5.81, and increasing level of RFC decreased pH from 5.99 to 5.85. Minimum daily ruminal pH decreased from 5.66 to 5.47 when level of RFC was increased, and decreased from 5.65 to 5.48 when forage particle size decreased. Time below pH 5.8 per day increased from 7.4 h to 10.8 h when level of RFC increased, and increased from 6.4 h to 11.8 h when forage particle size was decreased. Area below 5.8 showed the same relationship with RFC and forage particle size. Also, forage particle size affected the postprandial pH pattern. Cows spent more time eating when fed CS compared with FS (274 vs. 237 min/d), and time spent eating decreased when level of RFC was increased (271 vs. 241 min/d). Decreasing forage particle size decreased time spent ruminating (485 vs. 320 min/d), rumination periods (15.3 vs. 11.7), and duration of rumination periods (29 vs. 26 min). Increasing level of RFC increased time spent ruminating per kg NDF intake (68.5 vs. 79.5 min/kg). Milk fat percentage was correlated to mean ruminal pH (r = 0.41), time spent below pH 5.8 (r = -0.55), and area below 5.8 (r = -0.57), but not to intake or chewing variables. DMI of particles retained on a screen equivalent in size to the top screen of the Penn State particle separator was the intake parameter explaining most of the variation in mean ruminal pH (r = 0.27) and was correlated to time spent ruminating (r = 0.61) and chewing (r = 0.61).
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| 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 teacher head, 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".