215 COMPARISON BETWEEN CONVENTIONAL DIRECT TRANSFER FREEZING AND VITRIFICATION FOR THE CRYOPRESERVATION OF <i>IN VIVO</i> EMBRYOS FROM BRAHMAN CATTLE
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Bibliographic record
Abstract
There is a need to develop an efficient cryopreservation technique for Brahman cattle embryos that would lead to improved success in the propagation of this breed. The objective of this study was to compare the post-thaw pregnancy rates in recipient cows after nonsurgical transfer of Brahman in vivo -derived embryos frozen in ethylene glycol (EG) and by a new vitrification (VT) method. Prior to the initial in vivo study, hatching rates were recorded 72 h post-thaw on 3 treatment groups (No treatment: 43/55, 78%; EG: 39/83, 47%; and VT: 33/103, 32%) of IVF embryos to determine if development could be achieved. This warranted Phase I: In vivo embryos were produced by multiple ovulation and nonsurgical embryo collections from Brahman cows 7 days post-estrus and AI. Embryos in morula/blastocyst stage of development were graded and maintained in holding medium (Vigro; Bioniche Animal Health, Inc., Belleville, Ontario, Canada) after collection, until randomly allocated for EG or VT protocols. Vitrification was performed using experimental media provided by a commercial company (V1: Vigro + 5 M EG; V2: Vigro + 7 M EG + 0.5 M Galactose + Ficoll; and Diluent: Vigro + 0.5 M Galactose) and by direct plunging into LN2 (Walker et al . 2005 Reprod. Fertil. Dev. 17, 153). Freezing was performed at 0.5°C min-1 from -6°C to -32°C, using a commercially available medium (Vigro Freeze Plus; Bioniche). All embryos were packaged in sterile 0.25-mL plastic straws to allow for direct transfer (DT). Embryos were stored in LN2, and later thawed and nonsurgically transferred to synchronized recipient cows on Day 7 of their cycle. EG straws were air-thawed 5 s and then thawed in 30°C H2O for 10 s. VT straws were air-thawed 10 s and then thawed in 37°C H2O for 20 s prior to shaking them down to mix columns. Pregnancy results evaluated by ultrasound on Day 35 for the presence of a fetus from 4 replicates were 27% for EG (3/11) and 8% for VT (1/13) embryos. Problems with VT straws cracking during air thawing led to a second trial (Phase II) which changed the direct plunging technique for VT to a vapor freeze of 1 to 15 min prior to plunging into LN2. Pregnancy results from 16 transfers were 38% for EG (3/8) and 50% for VT (4/8) embryos, with no straws cracking. Although the number of observations is small, the results obtained showed that VT-DT is satisfactory for producing pregnancies comparable to EG-DT. Further research is required to confirm the results obtained in this preliminary study, and to test whether this method will allow the successful production of pregnancies under different environmental and field conditions.
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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 it