How does increasing protein supply or glucogenic nutrients modify mammary metabolism in lactating dairy cows?
Notice bibliographique
Résumé
In lactating dairy cows, yields of milk lactose and protein increase in response to increasing supply of intestinal protein or glucogenic nutrients (GN: ruminal infusion of propionic acid or post-ruminal infusion of glucose), but to a different extent. What are the common and the different changes in mammary metabolism explaining that both type of nutrients (protein or GN) increased both yields of protein and lactose? To answer this question a meta-analysis on mammary uptake data was performed. To analyse intra mammary metabolism and to estimate the requirement and supply of ATP to support the increases in milk synthesis, a modelling approach was performed on one study. Increased protein yield was associated with an increase in mammary net uptake of AA from group I (His, Met, Phe+Tyr), in response to extra protein or extra GN. However, this increased uptake was achieved differently. In response to protein supply, it was linked to an increase in mammary arteriovenous differences whereas in response to GN, it was linked an increase (tendency) in mammary plasma flow. In response to increasing protein supply, the mammary uptake of essential AA from group II (Ile, Lys, Leu and Val) as well as their ratio of mammary uptake to milk output (>1) also increased. This brought extra carbon skeletons and nitrogen for mammary synthesis of other components as non essential AA (NEAA), whereas the mammary uptake of two NEAA, Ala and Glu decreased. By contrast, NEAA uptakes (Ala and Glu) increased in response to GN supply (quadratic effect). Milk fatty acid synthesis was only increased in response to increasing protein supply, supported by an increase in b-hydroxybutyrate (BHBA) uptake. If lactose yield increased in parallel to milk protein yield both in response to protein or GN supply, glucose uptake did not follow lactose yield. Mammary glucose partition between lactose and oxidative pathways seemed a key mechanism to explain the increased lactose yield, in particular in response to GN supply. The increased protein synthesis was the only synthesis that required a substantial increase in ATP production, based on the modelling approach. The extra ATP required could be supplied by the catabolism of BHBA and group II AA in response to protein or the catabolism of extra glucose and lactate in response to GN supply. This meta-analysis confirms that the increase in uptake of AA from group I is a common mechanism to support an increase in milk protein yield. It also confirms that the regulation of the partition of their precursors (acetate, glucose, BHBA, group II AA and NEAA) towards milk components synthesis or oxidation is probably one of the key factors in the regulation of milk volume and composition.
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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 | 0,001 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,001 | 0,000 |
| Méta-épidémiologie (sens large) | 0,001 | 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 | 0,001 | 0,001 |
| Intégrité de la recherche | 0,002 | 0,001 |
| 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.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».