PSVIII-A-4 Evaluation of Blood Parameters Associated to Environmental Stress in Grazing Beef Heifers with Divergent Residual Feed Intake
Notice bibliographique
Résumé
Abstract There is considerable interest in improved feed efficiency to enhance sustainability in beef production, but a lack of understanding exists on the interaction between residual feed intake (RFI) and environment while grazing. Increasing variation in environmental conditions has been documented in western Canada with summers becoming warmer. This study evaluated blood parameters and rumen temperature (RT) of grazing beef heifers with divergent residual feed intake (RFI) during summer (July to August) of 2022. Forty-four crossbred beef heifers (358 ± 4.78 kg body weight; approximately 14 months of age) previously tested for RFI in drylot and classified as more (n = 21; LOW-RFI = -0.9 ± 0.70) or less feed efficient (n = 23; HIGH-RFI = 1.3 ± 1.00) were grazed at 2.72 AUM/ha over 7 wk in Alberta, Canada. Rumen temperatures were automatically recorded throughout the study using the Smart Rumen Bolus by Moonsyst. Plasma was collected every 14 ± 1 d for 42 d 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), and gamma-aminobutyric acid (GABA). Environmental conditions were assessed by calculating the Climate Comprehensive Index using temperature, wind speed, solar radiation, and humidity data from a weather station within 1 km of the grazed pastures. Daily weather conditions were considered to impose risk to cause mild, moderate, severe, and extreme stress for 8, 21, 8, and 1 days, respectively. Plasma and RT data were analyzed as a completely randomized design with repeated measures. An RFI × day interaction was observed for BUN (P = 0.018). LOW-RFI had greater (P = 0.02) BUN on d 42 compared with HIGH-RFI heifers (42.5 vs. 32.6 mg/dL, respectively), while GABA tended to be greater (P ≤ 0.09) for HIGH-RFI heifers on d 0 and 42. Free T3 concentrations were greater (P = 0.04; 8.54 vs. 7.78 pmol/L, respectively), whereas HP was less (P = 0.01) in LOW-RFI heifers. However, HP concentrations were below the threshold for inflammation throughout the study. There was also an effect of day (P < 0.01) for fT3, IGF-1, LEP, NEFA, HSP70, and BHBA. Leptin and HSP70 concentrations were greatest on d 14 and 28, whereas BHBA was the greatest (P < 0.01) and IGF-1 the least on d 42 (P < 0.01). An RFI × hour interaction was detected for RT (P = 0.0003), where HIGH-RFI heifers had greater RT throughout the day. In summary, weather conditions in western Canada changed blood parameters of replacement beef heifers during summer. Feed efficient heifers had decreased RT and greater plasma concentrations of fT3, which could be associated with metabolic homeostasis and regulation of thermogenesis.
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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 ».