176 EFFECTS OF VEHICLE AND ROUTE OF ADMINISTRATION OF LETROZOLE ON OVARIAN FUNCTION IN CATTLE
Notice bibliographique
Résumé
Treatment with letrozole, a non-steroidal aromatase inhibitor, has been associated with elevated mean plasma LH concentrations, a prolonged period of dominance of the extant dominant follicle, and delayed emergence of the next follicular wave in cattle. As well, a luteotrophic effect was hypothesised by the observation that CL diameter was increased in heifers given 250 µg kg–1 of letrozole divided in a 3-day regimen. The objective of the present study was to determine the effects of vehicle and route of administration of letrozole on ovarian function in sexually mature beef heifers. Ovarian function was synchronized among heifers using transvaginal ultrasound-guided follicular ablation followed by a luteolytic dose of PGF b.i.d. 4 days later. The ovaries were subsequently examined daily by transrectal ultrasonography until ovulation was detected. On Day 3 (Day 0 = ovulation), heifers were assigned randomly to 4 treatment groups and given letrozole at a dose of 1 mg kg–1 intravenously (i.v. in benzyl alcohol, n = 10) or intramuscularly (i.m. in benzyl alcohol plus canola oil 1:1 v/v, n = 10), or given a placebo (i.v. in benzyl alcohol, n = 5) or (i.m. in benzyl alcohol plus canola oil 1:1 v/v, n = 5). The ovaries were monitored daily by ultrasonography, and blood samples collected twice daily by jugular venipuncture from pre-treatment to post-treatment ovulations. Comparisons among groups were made by 1-way ANOVA for single-point measurements and by ANOVA for repeated measures for time-series data. The interovulatory interval did not differ among groups, nor did the day-to-day diameter profile of the dominant follicle of wave 1 (first follicular wave after ovulation). However, the interval between emergence of waves 1 and 2 was longer in heifers treated with letrozole i.m. (11.7 ± 0.3 days) than in controls (10 ± 0.4 and 9.5 ± 0.5 days for i.v. and i.m. controls, respectively; P < 0.05), and intermediate in heifers given letrozole i.v. (10.6 ± 0.30 days). The day-to-day diameter profile of the corpus luteum was greater (P < 0.05), and plasma progesterone concentrations tended to be greater (P < 0.06) in heifers treated i.m. with letrozole v. placebo. Plasma LH concentrations did not differ among groups, whereas plasma FSH concentrations were greater (P < 0.02) in heifers treated i.v. with letrozole v. placebo. In summary, letrozole dissolved in benzyl alcohol and given intravenously at a dose of 1 mg kg–1 on Day 3 did not alter ovarian function in cattle, but the same dose given i.m. in canola oil vehicle resulted in a longer inter-wave interval, a greater CL diameter profile, and greater plasma progesterone concentrations. We conclude that i.m. letrozole in oil is a feasible route of administration and vehicle for the development of an aromatase inhibitor-based treatment for herd synchronization in cattle. Research supported by the Natural Sciences and Engineering Research Council of Canada, Canadian Institutes for Health Research, and Bioniche Life Science Inc.
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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) | 0,001 | 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 | 0,000 | 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 ».