Effect of prepartum photoperiod and melatonin feeding on milk production and prolactin concentration in dairy heifers and cows
Bibliographic record
Abstract
Holstein multiparous cows (n = 29) and primiparous heifers (n = 32) calving over a 1-yr period were subjected to photoperiod-melatonin treatments according to a 2 × 3 factorial design. Starting 8 wk before expected calving, all animals were subjected to 1 of the following treatments: 8h of light and 16 h of dark (8L:16D), 16 h of light and 8h of dark (16L:8D), or 16L:8D plus melatonin feeding (16L:8D-melatonin). Each day at 1355 h, the animals in the melatonin treatment received orally a gelatin capsule containing 25mg of melatonin. The treatments ended at calving, when the animals were moved to the lactation barn; all animals were then subjected to about 16 h of light per day. At the beginning and end of the treatment period before calving, blood samples were taken from 6 heifers and 6 cows through a jugular cannula for 24h at 30-min intervals to monitor serum melatonin and prolactin concentrations. Milk production in the heifers was not affected by the photoperiod treatments. Early-lactation milk production was higher in the cows exposed to the short-day photoperiod than in those exposed to a long-day photoperiod (16L:8D and 16L:8D-melatonin), with averages of 36.7 ± 0.9, 33.1 ± 0.8, and 34.1 ± 0.9 kg/d for 8L:16D, 16L:8D, and 16L:8D-melatonin, respectively. Photoperiod had no effect on late-lactation milk production in the cows. During lactation, the dry matter intake of heifers was not affected by the treatments, but dry matter intake of the cows exposed to a short-day photoperiod was greater than that of the cows exposed to a long-day photoperiod. Feed efficiency of heifers was improved by short-day photoperiod. During the treatment period, prolactin concentration was lower in the animals exposed to a short-day photoperiod than in those exposed to a long-day photoperiod, was lower with the 16L:8D-melatonin treatment than with the 16L:8D treatment, and tended to be lower with the 8L:16D treatment than with the 16L:8D-melatonin treatment, with averages of 3.5 ± 0.8, 9.9 ± 0.8, and 6.0 ± 0.8 ng/mL for 8L:16D, 16L:8D, and 16L:8D-melatonin, respectively. In early lactation, prolactin concentration was lower in the heifers exposed to the 16L:8D photoperiod during the dry period than in those exposed to the 8L:16D photoperiod or fed melatonin. In conclusion, a short-day photoperiod during the dry period transiently increases milk production of cows and the feed efficiency of heifers in the following lactation. However, melatonin cannot be used to mimic a short-day photoperiod during the dry period.
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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 | 0.002 | 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 | 0.001 |
| Scholarly communication | 0.000 | 0.001 |
| 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".