The effect of yearling weight on fertility measures in Holstein heifers and primiparous cows
Notice bibliographique
Résumé
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
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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,001 | 0,002 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,001 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».