Weather Resilience in Grazing Beef Heifers with Differing Residual Feed Intake
Notice bibliographique
Résumé
The beef industry seeks sustainability through improved feed efficiency, yet the interaction between residual feed intake (RFI) and weather resilience in grazing beef heifers remains underexplored. This thesis evaluated rumen temperature (RT), blood parameters, growth performance, and activity behavior of beef heifers with varying RFI during summer and winter seasons in Western Canada. Forty-one crossbred beef heifers [351 ± 40 kg body weight (BW); 14 mo of age] were classified as more (LOW-RFI; n = 21, -0.96 ± 0.70) or less (HIGH-RFI; n = 20, 1.4 ± 1.00) feed-efficient. Heifer behavior was monitored using accelerometer-based sensors and individual virtual fence collar technology. Rumen temperature and water access events frequency were monitored using a bolus device, and blood samples were collected to analyze parameters related to protein, lipid, and growth metabolism, as well as neurotransmitters and hormones associated with metabolic homeostasis. The neutrophil-to-lymphocyte ratio (N:LR) was also assessed as a marker of inflammation. Environmental conditions were estimated by calculating the Climate Comprehensive Index. In summer, LOW-RFI heifers tended to exhibit greater free triiodothyronine levels (P = 0.08) and gamma-aminobutyric acid (GABA; P = 0.01) when weather was classified to impose moderate stress. LOW-RFI heifers also tended to produce more heat shock protein 70 (P = 0.10), while HIGH-RFI heifers had greater haptoglobin (P = 0.02) and leptin (P =0.04) concentrations. The RT was greater in HIGH-RFI heifers during specific hours of the day (P = 0.002). For activity behavior, HIGH-RFI heifers had a greater number of steps on certain days, sought shade and water spots during hotter days, and had more daily transitions. In winter, greater leptin concentrations were found in HIGH-RFI heifers (P = 0.04) while GABA tended to decrease in HIGH-RFI (P = 0.08). The LOW-RFI heifers had higher RT on certain days (P = 0.009), more standing activity during moderate cold stress, and higher N:LR on the coldest days. The HIGH-RFI heifers stood more on extreme cold days but had fewer steps on mild cold days and more steps on severe cold days. LOW-RFI heifers had fewer daily transitions. Blood parameters were significantly affected by day, RFI and RFI × day interaction in both seasons (P < 0.001), but there was no significant difference in growth performance between LOW and HIGH-RFI heifers (P > 0.24). Feed-efficient beef heifers in Western Canada exhibited greater resilience to extreme weather conditions, showing variations in blood parameters and rumen temperature (RT) without affecting growth performance. This study identified distinct behavioral and physiological responses between LOW-RFI and HIGH-RFI heifers. LOW-RFI heifers displayed enhanced thermoregulatory activity during both summer and winter, although chronic cold exposure may have potentially negative consequences. These findings explain the potential of selecting LOW-RFI heifers, leading to environmental resilience and sustainable beef production. However, further research is necessary to understand the long-term impacts of chronic cold stress on LOW-RFI heifers.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
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) | 0,003 | 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.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».