Effects of Exposure to Heat Stress During Late Gestation on the Daily Time Budget of Nulliparous Holstein Heifers
Bibliographic record
Abstract
Exposure of dairy cows to heat stress negatively affects welfare and performance during all phases of the lactation cycle. Detrimental effects include decreased milk and reproductive performance, reduced immune status and health, and altered natural behaviors. While we understand how mature cows respond to heat stress, the effects of late gestation heat stress on pregnant heifers is still unknown. Automated monitoring devices were used to document the behavioral activity of heifers during the pre- (final 60 d of gestation) and postpartum (first 60 d of lactation) periods. Twenty-five pregnant Holstein heifers were housed in a free-stall barn and enrolled to heat stress (HT; shade; n = 13) or cooling (CL; shade, soakers and fans; n = 12) treatments during the last 60 days of gestation. All animals were provided active cooling postpartum. Upon enrollment, heifers were fitted with a leg tag, which measured daily lying time, number of steps, and standing bouts, and a neck tag that measured eating and rumination times. Rectal temperatures (RT) and respiration rates (RR) were measured thrice weekly during the prepartum period. Relative to CL, HT heifers had elevated RT (38.8 vs. 38.7 ± 0.04°C) and RR (59.6 vs. 44.4 ± 1.9 breaths/min) during the prepartum period. Heat-stressed heifers tended to spend more time eating (224 vs. 183 min/d) and less time ruminating (465 vs. 518 min/d) during the prepartum period compared to CL, but dry matter intake did not differ. During the postpartum period, HT heifers spent more time eating (209 vs. 180 min/d) during weeks 1–4 of lactation, but rumination time was similar. Lying time was reduced by 59 and 88 min per day during weeks −7 and −6 prepartum and 84 and 50 min per day during weeks 2 and 3 postpartum in HT heifers, relative to CL. The number of steps was greater for HT during the postpartum period, from weeks 2 to 9 (3019 vs. 2681 steps/d). Eating frequency was similar during pre- and postpartum periods, however, based on semi quantitative visualization of the smarttag reports, HT consumed larger meals at night during the pre- and postpartum periods compared with CL heifers. In summary, late-gestation exposure to heat stress affects the daily time budget of first lactation heifers during both the pre- and postpartum periods. Current insights of heat stress effects on behavioral responses of dairy heifers may contribute to the development of more effective management strategies to mitigate heat load.
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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 | 0.000 |
| 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) | 0.001 | 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".