PSVIII-11 Cold stress responses in beef heifers with divergent residual feed intake
Notice bibliographique
Résumé
Abstract Beef cattle have been selected for feed efficiency to reduce feeding costs and environmental impact. Still, there is a paucity of knowledge on how feed-efficient beef females maintained outdoors respond to extreme cold weather. Therefore, this research assessed blood parameters and rumen temperature (RT) of beef heifers with divergent residual feed intake (RFI) during winter in Alberta, Canada. Ccrossbred beef heifers [n = 41; body weight (BW) = 474 ± 38; approximately 21 mo of age) previously tested for RFI in drylot and classified as either more (n = 21; LOW-RFI = -1.0 ± 0.70) or less feed-efficient (n = 20; HIGH-RFI = 1.4 ± 1.00) were used in a completely randomized design for 55 d (January to March). Heifers were maintained in a single dormant pasture and received free-choice hay. A Smart Rumen Bolus (Moonsyst) was used to automatically record RT. Blood samples were collected every 18 ± 8 d based on weather conditions to determine concentrations of blood urea nitrogen (BUN), non-esterified fatty acids (NEFA), insulin-like growth factor 1 (IGF-1), β-Hydroxybutyric acid (BHBA), leptin (LEP), free triiodothyronine (fT3), haptoglobin (HP), heat shock protein 70 (HSP70), gamma-aminobutyric acid (GABA), and serotonin (5-HT). Environmental conditions were assessed by calculating the Climate Comprehensive Index (CCI) using temperature, wind speed, solar radiation, and humidity from a weather station within 1 km of the pasture. Based on CCI, daily weather conditions were considered to impose mild, moderate, severe, extreme, and extremely dangerous stress risk for 3, 15, 19, 13, and 5 d of the study, respectively. Leptin was greater in HIGH vs. LOW-RFI heifers (P = 0.05; 5.21 vs. 4.56 ng/ml). A tendency for an RFI × day interaction was detected for GABA (P = 0.09) and HP (P = 0.06), with greater concentrations in the LOW-RFI heifers on extreme and extremely dangerous cold days, respectively. However, HP concentrations were below the threshold for inflammation throughout the study. An effect of day was detected for IGF-1, LEP, BUN, NEFA, BHB, and 5-HT (P ≤ 0.001). The least concentrations of BHBA and BUN (128 nmol/L and 4.8 mg/dL, respectively) were recorded, along with the greatest NEFA concentration (0.619 mEq/L), during an extremely dangerous cold day. On extreme cold days, LEP (3.7 ug/L) was the least and 5-HT was the greatest (56.7 ng/mL). Rumen temperature was greater in LOW-RFI vs. HIGH-RFI when day imposed greater risks to cause cold stress (P = 0.01). However, no differences were detected in final BW or average daily gain (P ≥ 0.24). In summary, results indicate differential blood parameter dynamics and rumen temperature fluctuations between high and low RFI heifers under varying cold stress conditions. Greater plasma leptin concentrations and decreased rumen temperature are likely associated with heightened thermogenic activity and cold stress in less-feed-efficient heifers.
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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 | 0,000 | 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) | 0,001 | 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 ».