222 THE USE OF IN VITRO FERTILIZATION TO STUDY BOVINE IDIOPATHIC INFERTILITY
Bibliographic record
Abstract
A 4-year-old beef bull underwent a breeding soundness evaluation at the Western College of Veterinary Medicine (Veterinary Hospital, University of Saskatchewan); no apparent abnormalities were observed after conventional semen evaluations. However, the clinical history of this bull indicated that no pregnancies resulted from natural service of 52 cycling cows over a period of 2 years. Completed services were observed. The objective of this study was to use in vitro fertilization (IVF) technology to evaluate whether the sperm from this infertile bull could successfully fertilize oocytes in vitro. Fresh semen was collected with an electroejaculator and frozen in a computer-controlled rate freezer. Concentration and motility parameters were assessed by using computer-assisted semen analyses. Sperm morphology was evaluated on eosin-nigrosin-stained slides, and Coomassie blue staining was used to evaluate the presence of intact acrosomes. Within each evaluation technique, frozen–thawed semen from bulls (n = 2) with proven fertility was used as a positive control and samples of dead sperm (produced by repeated frozen–thawed cycles until reaching no sperm motility) were used as a negative control. Frozen semen from the infertile bull was used for IVF assay. Data were analyzed by ANOVA (sperm motility and the presence of acrosomes) or the chi-square test (cleavage and blastocyst rates), with a P-value of 0.05. Our infertile bull showed an average motile sperm percentage of 91.7 ± 2.2%, with 78.6 ± 3.5% progressive motility. After cryopreservation procedures, frozen–thawed semen had an acceptable general and progressive percentage of motility of 57.8 ± 6.7% and 43.9 ± 9.2%, respectively. Sperm stained with Coomassie blue showed a greater proportion of intact acrosomes in the fresh semen (63.6 ± 4.3% v. 40.4 ± 3.7%; P < 0.05); however, frozen–thawed semen from both the fertile bull and the control were similar (40.4 ± 3.7b% v. 45.5 ± 2.2b%, P < 0.05). In vitro fertilization results revealed a low cleavage rate at 48 h postfertilization (19.8 ± 6.3%) and blastocyst rate (2.4 ± 2.8%) when using frozen–thawed semen from the infertile bull, compared with the control (56.7 ± 8.2% and 26.3 ± 4.5%, respectively; P < 0.001). Moreover, cleavage and blastocyst rates obtained by using the negative control (21.1 ± 3.2% and 1.1 ± 1.9%, respectively) were similar to those of the infertile bull (P > 0.10). It was noted that ova fertilized with either frozen–thawed semen from the infertile bull or the negative control did not produce blastocysts before Days 8 and 9 of embryo culture, which is a characteristic of parthenogenesis. The results from this IVF study suggest that in this bull, there was a missing or defective factor blocking one of the steps in the fertilization process. Further investigations to identify this factor will increase our knowledge of male fertility, and could lead to new methods of evaluating and regulating fertilizing ability.
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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 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| 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".