68 REPRODUCTIVE PERFORMANCE OF CLONED BULLS
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Notice bibliographique
Résumé
The generation of cloned animals by somatic cell nuclear transfer has been reported in a number of countries worldwide. However, progress has been impeded by the extremely low efficiency of cloning and health of some of the cloned animals. Surprisingly, little is known of the reproductive performance of viable clones when compared to the original cell donor, given that a major motivation of cloning is dissemination of superior genotypes. The aim of this study was to compare semen collected from three cloned bulls (Clones A1, B1, and B2) to that of the original donor bulls (Donors A and B). Parameters examined included ejaculate volume, sperm concentration and the motility characteristics of frozen/thawed semen using computed-assisted semen analysis (Hamilton Thorne Biosciences, Inc., Beverly, MA, USA). The fertilization ability of each semen sample was examined using in vitro matured oocytes derived from abattoir-source ovaries. Frozen/thawed semen samples from donor and cloned bulls were prepared on a Percoll gradient and diluted with fertilization medium to a concentration of 1 million sperm/mL prior to fertilization (IVF). The number of blastocysts and total cell counts were analyzed on Day 7 of culture. Finally, in vitro-fertilized blastocysts (Day 7) were transfer to synchronized recipients (n = 49) to examine in vivo development. Proportional data for the in vitro development of embryos and subsequent pregnancy rates were analyzed by chi-square test, and embryo cell numbers were analyzed using Student's t-test. Progressive motility percentage between donor and cloned bull did not differ: Donor A (62.25 ± 3.89, n = 12); Donor B (66.69 ± 4.47, n = 13); Clone A1 (71.37 ± 8.57, n = 8); Clone B1 (73.75 ± 2.42, n = 12); Clone B2 (72.41 ± 3.26, n = 12). No obvious differences in kinetic motility parameters were evident between cloned and non-cloned donor animals. However, blastocyst rates were significantly higher in cloned bulls (Clone A1: 30.9%, 81/262; Clone B1: 34.4%, 98/285; and Clone B2: 42.9%, 120/280) compared to donor bulls (Donor A: 20.7%, 54/261; Donor B: 20.9%, 76/364). Total embryo cell numbers did not differ significantly between donor bulls (Donor A: 138.3 ± 5.3, n = 39; Donor B: 133.2 ± 5.2, n = 47) and cloned bulls (Clone A1; 126.3 ± 4.4, n = 45; Clone B1: 134.4 ± 7.1, n = 26; and Cloned B2: 140.1 ± 3.9, n = 46). Initial pregnancy rates on Day 30 were also not different between Donor A (42.3%, 11/26) and Clone A1 (47.8%, 11/23). Preliminary observations from the small data set on postpubertal cloned bulls indicate that semen production, semen morphology, and reproductive performance (in vitro and in vivo) were similar in terms of semen characteristics and reproductive performances when compared to their original donor bulls.
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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 | 0,001 |
| 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) | 0,000 | 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 découle