Growth, appetite, and mineral deposition in rainbow trout reared in fresh- or seawater under different CO2 regimes
Notice bibliographique
Résumé
Despite degassing efforts in recirculating aquaculture systems (RAS) and short hydraulic retention time in rearing units, carbon dioxide (CO 2 ) concentrations reach a hypercapnic steady state. Furthermore, as CO 2 excretion is correlated with the oxygen consumption of fish and bacteria, CO 2 levels in RAS may undergo fluctuations, of greater or smaller magnitude, depending on systems design and operation. Experimental approaches to assess the effects of CO 2 on fish usually subject fish to constant CO 2 concentrations, which might not reflect rearing conditions on an industrial production scale. Here, we compare the effects of oscillating against constantly elevated CO 2 levels on the appetite, growth, feed utilization, and mineral deposition in three separate growth trials. Two trials were conducted in freshwater (FW) and one in seawater (SW). In each trial, rainbow trout ( Oncorhynchus mykiss ) were subjected to four different CO 2 treatments: either constant levels of 10 mg/L CO 2 ( p CO 2 = 3.86 mmHg in FW / 4.57 mmHg in SW), 25 mg/L CO 2 ( p CO 2 = 9.65 mmHg in FW / 11.42 mmHg in SW), fluctuating between these two concentrations over 24 h, or normocapnic control conditions of ≤3 mg/L CO 2 ( p CO 2 ≤ 1.16 mmHg in FW / 1.37 mmHg in SW) for at least 5 weeks on fixed daily rations of 1.3 % of the tank biomass. In one of the freshwater trials, the diet contained high levels of phosphorus (1.8 %) to assess if elevated dietary phosphorus concentrations promoted mineralization in kidney tissues (nephrocalcinosis) under hypercapnic conditions. In both freshwater trials, fish at all CO 2 levels accepted the offered feed, while in seawater daily feed intake was reduced by 35 % at exposure to 25 mg/L CO 2 ( p CO 2 = 11.42 mmHg). Despite accepting the full, albeit restricted ration, fish reared in freshwater showed that CO 2 affected appetite, evidenced by changes in mRNA expression of appetite-regulating peptides in the hypothalamus and liver of the fish. This finding was confirmed by a maximum voluntary feed intake test, showing that fish consumed less food at higher CO 2 concentrations. Despite consuming similar daily ration sizes, the specific growth rate (SGR) and feed conversion ratio (FCR) were significantly affected in the 25 mg/L freshwater group ( p CO 2 = 9.65 mmHg) but not at 10 mg/L ( p CO 2 = 3.86 mmHg) or when oscillating between those concentrations. In the seawater trial, however, SGR and FCR of the trout were already significantly reduced at 10 mg/L of dissolved CO 2 ( p CO 2 = 4.57 mmHg) compared to the control group, but even more so in the 25 mg/L CO 2 group ( p CO 2 = 11.42 mmHg). While the CO 2 regimes applied in this study and high dietary phosphorous did not result in clear macroscopic pathologies indicative of nephrocalcinosis, there was calcium deposition in trout kidneys was highly elevated in the 25 mg/L group ( p CO 2 = 9.65 mmHg), indicating the potential onset of this pathology, which was supported by histopathological examinations. Overall, the results of this study show that while fish were affected by CO 2 in all trials, the severity depends on water chemistry. • High [CO 2 ] (25 mg/L) affected appetite, growth, and kidney mineral deposition • The relationship between [CO 2 ] against growth and feed utilization was linear • Detrimental effects of CO 2 were more severe in seawater than in freshwater • Fluctuating [CO 2 ] affected the fish less than constant high [CO 2 ] (25 mg/L) • High dietary phosphorus levels caused increased nephrocalcinotic kidney lesions
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 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) | 0,001 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,001 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,001 |
| Intégrité de la recherche | 0,000 | 0,001 |
| 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 ».