Weight, height, and relative-reliability indicators as a management tool for reducing age at first breeding and calving of dairy heifers
Bibliographic record
Abstract
In Québec first calving occurs on average at 27 mo, whereas the target is 23 to 24.5 mo to maximize herd profitability. The aim of this study was to quantify current and future heifer growth using individual heifer random regressions and to generate indicators (such as heifer weight and height at 15 and 24 mo, average daily gain before and after 15 mo, age at which optimal weight for breeding is attained, i.e., 55% of mature weight, and reliability of the 15- and 24-mo weight predictions) that could be used as a practical on-farm tool. Dairy heifer weight estimated by heart girth circumference and height measured at the withers (from 0 to 27 mo) were obtained from the Valacta database (DHI agency, Ste-Anne-de-Bellevue, QC, Canada) from 1995 to 2012. Indicators were calculated based on the current situation of Holstein (HO), Ayrshire (AY), Jersey (JE), and Brown Swiss (BS) heifer growth in Québec. Heifers with less than 2 records were excluded from the analysis. Mature weights were determined by weight at calving of cows from third or greater lactation for a given breed and were 710 kg for HO, 625 kg for AY, 470 kg for JE, and 670 kg for BS. Estimated weights at 15 and 24 mo were 425 and 627, 334 and 482, 297 and 429, and 379 and 560 kg for HO, AY, JE, and BS, respectively, which are heavy enough for breeding and calving, except for AY. Relative reliabilities of the 15- and 24-mo weight predictions were on average 89 and 60%, respectively, based on measurements up to 15 mo. For HO, AY, JE, and BS, wither heights at 15 and 24 mo were 134 and 143, 125 and 134, 122 and 131, and 130 and 140 cm, respectively. Age at optimal breeding weight was 13.6, 15.5, 12.6, and 14.5 mo for HO, AY, JE, and BS, respectively. These data suggest that it is realistic to expect a first calving at 24 mo for HO, JE, and BS. A growth delay was observed for AY; average daily gain was 655 and 538 g/d before and after 15 mo, respectively. The average daily gain before and after 15 mo was 848 and 747 g/d for HO, 603 and 486 g/d for JE, and 775 and 662 g/d for BS, respectively. These indicators could be calculated for an individual heifer and on a herd-level basis and used on farm as a management tool for reducing age at first breeding and at first calving.
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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 | 0.002 | 0.003 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 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".