12 Effect of additional prostaglandin F2a during the Ovsynch protocol applied in different postpartum intervals in lactating dairy cows: Preliminary results
Bibliographic record
Abstract
Timed AI (TAI) programs have been developed to increase the service risk. However, when Ovsynch is used as a synchronization protocol, lack of regression of the corpus luteum after prostaglandin F2a (PGF) administration has been demonstrated, leading to reductions in fertility. In this way, a second PGF administration might increase the frequency of achieving complete luteolysis. This study aimed to evaluate the effect of an additional treatment with PGF on fertility when an Ovsynch synchronization protocol was applied at different postpartum intervals. Multiparous high-production dairy cows (n = 471) of a commercial farm were stratified by postpartum intervals [<120 (n = 136), 120-150 (n = 131), 150-180 (n = 92), 180-210 (n = 52), and >210 days (n = 60)] and randomly allocated to receive either the Ovsynch (n = 108) or Ovsynch with second PGF protocol (n = 243). Cows inseminated 12 h after observed heat detection (AI) served as a control (n = 120). The Ovsynch protocol consisted of an injection of gonadotropin-releasing hormone (100 µg; Fertagyl®, Intervet, Millsboro, MD, USA) on Day 0, an injection of PGF (0.5 mg; Estrumate®, Schering-Plough Animal Health, Montréal, QC, Canada) on Day 7, another injection of gonadotropin-releasing hormone (100 µg) on Day 9, and timed insemination on Day 10. The Ovsynch with second PGF protocol consisted of the same hormone injection schedule as the Ovsynch protocol, but a second injection of PGF (0.5 mg; Estrumate®) was administered 24 h after the first PGF. Data were analysed using the chi-square test. The level of significance was taken as P < 0.05. When data were pooled at 120 to 150 days of postpartum interval, pregnancy rate was higher, but not significantly different (P > 0.05), for cows that received the Ovsynch (37.5%, n = 32) or Ovsynch with second PGF protocol (33.8%, n = 77) compared to nonsynchronized cows (22.8%, n = 22). After 180 days of postpartum interval, Ovsynch with second PGF protocol triggered pregnancy rates similar to those of nonsynchronized cows (33.3%, n = 21 and 28.6%, n = 14), whereas the Ovsynch protocol resulted in lower percentages (11.8%, n = 17; P > 0.05). Similar pregnancy rates (P > 0.05) were observed when TAI protocols were administered before 120 days (26.5 and 30.2% for Ovsynch and Ovsynch with second PGF, respectively) or between 150 and 180 postpartum days (31.8 and 33.9% for Ovsynch and Ovsynch with second PGF, respectively) compared with AI cows (25.7 and 28.8% for <120 days and between 150 and 180 postpartum days, respectively). These preliminary results showed a tendency of a better pregnancy rate when both TAI synchronization protocols were applied between 120 and 150 postpartum days when compared with AI. Also, the application of a second dose of PGF seems recommendable when the Ovsynch protocol is used to synchronize cows of >180 postpartum days. Ongoing research will allow an increase in the number of the samples in each postpartum interval in order to confirm these results.
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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".