The effect of yearling weight on fertility measures in Holstein heifers and primiparous cows
Bibliographic record
Abstract
The Canadian dairy industry consists of approximately 10,000 dairy farms with about 1.4 million head dairy cattle population, 70% of which are cows, and the rest are heifers. Cows constitute the productive segment of the herd, as they produce milk whereas the heifers form the non-productive segment. However, the heifers are equally important as they determine the future of the herd. After attaining puberty, the heifers become reproductively active and capable of replacing the dairy cows in the herd that may fail to reproduce or are culled from the herd. A producer should, therefore, select heifers with a good reproductive potential as replacements for the herd. Data from the Québec Dairy Herd Improvement Agency (Valacta) were analysed to determine the relationship between yearling weight in Holstein heifers and various fertility measurements in heifers and primiparous cows. The fertility parameters analyzed, depending on developmental stage included: Days to first service; Number of services for conception; Days from first to successful breeding; Days open; and Calving Interval (first to second calving). Since yearling body weights were rarely reported, yearling weight in heifers was predicted from available weight data, using the approach of Cue et al. (2012). The study covered a period of 8 years from 2008 – 2015, and the fertility parameters were analyzed as three groups: heifers that had a successful first calving; cows that had both a first and a second calving; and cows that had a first calving but failed to conceive a second time. Results showed that predicted yearling body weight had a significant effect on only some fertility traits of heifers; heifers that were predicted to weigh less than 300 kg at 12 months of age required a significantly fewer number of services to conception and had a significantly fewer number of days between first and successful breeding. In cows that failed to conceive the second time, the interaction between predicted weight at 12 months of age and age at first calving, had a significant effect on days to first service. Predicted body weight at 12 months did not have a significant effect on other fertility measures in those two data sets, and no significant effect on any of the fertility parameters in the data set of cows that that had both a first and a second calving. Not surprisingly, an earlier age at first calving had a significant effect on most first-lactation measures of fertility, as well as on days open and calving interval in cows that had both a first and a second calving. The data also demonstrated a considerable proportion of first calvers that failed to have a second conception. In conclusion, body weight at 12 months had no significant effect on post-first calving fertility measures. However, a lack of actual body-weight measurements in the data should not be overlooked (animals with no recorded weight prior to first calving could not receive a predicted body weight at 12 months), and this emphasises the importance of data recording for a better understanding of the dairy industry’s reproductive challenges
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.002 |
| 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".