9 TIMED ARTIFICIAL INSEMINATION IN BLOCKS: A NEW ALTERNATIVE TO IMPROVE FERTILITY IN BEEF COWS
Bibliographic record
Abstract
The objective of this study was to evaluate whether timed artificial insemination (TAI) according to the diameter of the dominant preovulatory follicle (POF) would improve pregnancy rates in beef cows. In Experiment 1, a retrospective meta-analysis of 5 oestradiol- or gonadotropin-releasing hormone-based TAI experiments from 2011 to 2014 was performed to evaluate the interval from luteolysis to ovulation. In these experiments, crossbred cows (Gyr × Holstein; n = 60) were examined by ultrasonography at 12-h intervals from progesterone-releasing device (CIDR) removal to ovulation. A linear regression model was used to predict the effect of POF diameter on the time of ovulation. Cows with a larger POF at the time of AI ovulated earlier than cows with smaller POF (y = –8.25x + 115.22; R2 = 0.93; P < 0.0001). In Experiment 2, lactating Nelore cows (Bos indicus; n = 59) on random days of the oestrous cycle were given 2 mg of oestradiol benzoate IM and a CIDR device (Day 0) to synchronize follicular waves. The CIDR were removed, and cows were given 500 µg of d-Cloprostenol (prostaglandin F2a) IM, 1 mg of oestradiol cypionate IM, and 300 IU of eCG IM on Day 8. On the morning of Day 10 (07:00 a.m.), the diameter of the POF was assessed by ultrasonography, and cows were randomised into Control (n = 29) and Block (n = 30) groups. 1) Control-group cows were TAI 48 h after CIDR removal (08:00 a.m. on Day 10), and Block-group cows were inseminated at 4 time points according to the diameter of the POF: B0 (POF =15 mm, TAI at 08:00 a.m. on Day 10, n = 6), B1 (POF 13 to 14 mm, TAI at 02:00 p.m. on Day 10, n = 8), B2 (POF 11 to 12 mm, TAI at 08:00 a.m. on Day 11, n = 11), and B3 (POF = 10 mm, TAI at 02:00 p.m. on Day 11, n = 5). Pregnancy status was assessed 30 days post-AI by ultrasonography. No differences were detected in the diameter of the POF 48 h after CIDR removal (P = 0.77) or ovulation rate (P = 0.65; combined ovulation rate 52/59, 88%) between Control and Block groups. Block group had a higher pregnancy rate than Control (22/30, 73% v. 13/29, 45%, respectively; P = 0.02). In conclusion, our results document that interval from luteolysis to ovulation depends on the size of preovulatory follicle, timing of AI in relation to ovulation time is critical, and AI time according to the diameter of the POF can be an effective tool to improve fertility of cows in TAI protocols.
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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 | 0.001 |
| 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) | 0.000 | 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".