Associations of acute stress and overnight heart rate with feed efficiency in beef heifers
Notice bibliographique
Résumé
Proxies have the potential to accelerate feed efficiency (residual feed intake (RFI); kg dry matter/day) improvement, assisting with the reduction of beef cattle feed costs and environmental impact. Heart rate (HR) (beats per minute (BPM)) is associated with feed efficiency and influenced by autonomic activity and peripheral metabolism, suggesting HR could be used as a proxy for feed efficiency. Objectives were to assess associations between overnight HR, lying patterns and RFI, and between acute stress HR and RFI. Heifer calves (n=107; 408±28 days of age, 341±42.2 kg) and yearling heifers (n=36; 604±92 days of age, 539±52.2 kg) were exposed to a performance test to determine productive performance. Overnight HR (electrode based) and lying patterns (accelerometer based) were monitored on a subgroup of heifer calves (n=40; 20 lowest RFI; 20 highest RFI). In the 10-min acute stress assessment, all heifers were individually exposed to the opening and closing of an umbrella and HR before (HRBEF), in response to (HRMAX), after (HRAFT) and change (HRCHG; HRAFT-HRBEF) as a result of exposure were determined. Using polynomial regression, rate of HR decrease pre-exposure (β 1) and rates of HR increase (β 2) and decrease (β 3, β 4) post-exposure were determined. Heifer calves in the overnight assessment were classified into equal RFI groups (low RFI; high RFI) and HR means were treated as repeated measures and compared using multiple regression. In the acute stress assessment, heifers were classified within cattle category into equal RFI groups (low RFI; high RFI) and means and polynomial regression parameters were compared using multiple regression. Low-RFI heifer calves had a lower overnight HR (69.2 v. 72.6 BPM), similar HR change from lying to standing intervals (8.9 v. 9.2 BPM) and similar time lying (61.1% v. 64.5%) compared with high-RFI heifer calves. Low-RFI heifer calves had a higher absolute HRMAX (162.9 v. 145.7 BPM) and β 2 (-0.34 v. -0.20) than high-RFI heifer calves. Low-RFI yearling heifers had similar acute stress HR means and a lower β 1 (0.003 v. 0.006) than high-RFI yearling heifers. Overnight HR and acute stress HR are potential indicators of RFI in heifer calves. However, acute stress HR results varied in yearling heifers, suggesting previous handling experience and/or age influence stress response. Pending further development (predictive ability, repeatability), the acute stress assessment could have potential for on-farm application as a feed efficiency proxy in young heifers with minimal handling experience.
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Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 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) | 0,000 | 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 tête enseignante, pas un consensus.
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