Physical and Functional Markers of Fertility in Holstein Bulls.
Bibliographic record
Abstract
Dairy bull semen often has wide variations in fertility, despite meeting minimum standards for quality. The objectives of this study were to compare testicular physical characteristics and sperm characteristics of Holstein bulls to identify fertility markers. Ten mature Holstein bulls (4-5 y old) were selected and classified as either low- or high-fertility (n=5 each) based on adjusted 56-d non-return rates. Scrotal measurements (scrotal circumference, scrotal neck circumference, scrotal neck length) and testicular dimensions, scrotal infrared thermograms, and testicular ultrasonographic data were recorded. Among all of these testicular physical characteristics, only testicular width was significantly lower for low- vs high-fertility bulls. Four ejaculates were collected from each bull and cryopreserved; frozen-thawed sperm from these samples were evaluated for viability, motion characteristics, ability to fertilize oocytes in vitro, and the developmental competence of resulting embryos. Flow cytometry-based analysis of sperm stained with SYBR14/PI demonstrated that low- and high-fertility bulls differed in sperm viability. The proportion of moribund sperm was higher in sperm from low- vs high-fertility bulls, and the proportion of moribund sperm were correlated with non-return rates. Based on a higher proportion of moribund sperm, expressed as a percentage of viable sperm in low- vs high-fertility bulls, we concluded that the rate of conversion of viable sperm to a moribund state was higher in low-fertility bulls, and that viability of sperm from low-fertility bulls was inherently compromised. Several sperm kinematic parameters were significantly correlated with non-return rates. Moreover, whereas post-thaw sperm from low-fertility bulls had a forward progressive motility pattern, sperm from high-fertility bulls were in transition to hyperactivated motility (based on linearity, curve line velocity and amplitude of lateral head displacement). Accordingly, a significantly lower percentage of hyperactivated sperm were present in the post-thaw semen of low- vs high-fertility bulls. Similarly, sperm selected through a sodium-hyaluronate swim-up medium (provided capacitating conditions) demonstrated that sperm from high-fertility bulls had a higher tendency to undergo hyperactivated motility. Following in vitro fertilization, the percentage of cleaved embryos were significantly lower in low- vs high-fertility bulls. In addition, 8-cell embryos, morulae, blastocysts, and hatched blastocysts (expressed as a percentage of cleaved embryos) were significantly lower in low- vs high-fertility bulls. In conclusion, testicular physical characteristics were not predictive of fertility in bulls producing semen with acceptable standards. However, proportion of moribund sperm present in frozen-thawed sperm, rate of conversion of viable sperm to a moribund state, CASA parameters, ability of sperm to undergo hyperactivation, ability of sperm to fertilize in vitro, and developmental competence of resulting embryos, were all predictive of fertility. This study received funding support from NSERC; L'Alliance Boviteq Inc., Saint-Hyacinthe, QC; Westgen, Milner, BC; Alberta Livestock and Meat Agency; and Agriculture & Food Council, AB. (poster)
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 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".