Effects of estradiol and oxytocin injection on the efficiency of artificial insemination in Iranian Zel ewes during the breeding season

Document Type : Original Articles

Authors

1 Department of Animal Sciences, College of Agriculture & Natural Resources, University of Tehran, Karaj, Iran

2 Department of Animal Sciences, Faculty of Agriculture, Islamic Azad University, Ghaemshahr Branch, Ghaemshahr, Iran

3 Department of Animal Sciences, College of Agriculture & Natural Resources, University of Tehran, Karaj, Iran; Razi Vaccine and Serum Research Institute, Agricultural Research, Education and Extension Organization, Tehran, Iran

4 Department of Animal Sciences, College of Agriculture & Natural Resources, University of Tehran, Karaj, Iran Department of Poultry Sciences, Faculty of Agriculture, Tarbiat Modares University, Tehran, Iran

5 Department of Poultry Sciences, Faculty of Agriculture, Tarbiat Modares University, Tehran, Iran

Abstract

In sheep industry, pregnancy rate after artificial insemination (AI) declines due to the complex anatomy of the cervix in ewes, such that it might prevent effective intrauterine insemination. At estrus, cervical relaxation occurs to some degree in ewes, which is regulated by the changes in the levels of reproductive hormones. This study aimed to evaluate the effects of estradiol and intravenous (IV) or intramuscular (IM) oxytocin injection at different doses on the cervical opening and pregnancy rate of Iranian Zel ewes during the breeding season. For this purpose, three experiments were conducted on 120 ewes (3-4 years old, weighing 47±2.5 kg). In the first experiment, ewes were equally assigned to two groups to receive estradiol (100-200 µg). After 12 h, each group was equally divided into six subgroups (n=20) and received 50, 100 and 150 IU oxytocin via IV and IM injection. Cervical opening was measured before and 15 min and 12 h after estradiol injection and 20 min after oxytocin administration. In the second experiment, we only assessed the effect of oxytocin administration on cervical opening similar to the first experiment. In the third experiment, controlled internal drug release (CIDR) was used in all the ewes for 12 days to induce estrus synchronization. Afterwards, the ewes received 550 IU intrauterine equine chorionic gonadotropin at the time of CIDR removal. Before AI, ewes were equally categorized into three groups (n=40); the first group was considered as control, and the other two groups received 100 IU oxytocin via IM or IV injection. At 54 h after CIDR removal, all ewes were inseminated transcervically using diluted fresh semen. Pregnancy was detected via ultrasound 50 days after insemination, and lambing and twinning rates were measured after parturition. Results of the first and second experiment indicated that estradiol injection had no effect on cervical opening (P>0.05), while the administration of 100 or 150 IU oxytocin (IV or IM) could dilate the cervix with or without estradiol (P<0.05). Furthermore, administration of 100 IU oxytocin (IV or IM) in the third experiment improved pregnancy and lambing rates compared to the control group (P<0.05); however, it had no effect on the twinning rate of the ewes (P>0.05). According to the results, IV or IM injection of oxytocin could improve the pregnancy rate in Iranian Zel ewes through the dilation of cervical canal. Therefore, it is suggested that this method be applied to enhance the pregnancy rate of ewes during the breeding season.

Keywords

Main Subjects

Article Title [French]

Les effets de l’estradiol et de l’injection d’ocytocine sur l’efficacité de l’insémination artificielle chez les brebis Zel iraniennes pendant la saison reproductrice

Abstract [French]

Dans l’industrie ovine, l’insémination artificielle (IA) engendre une diminution du taux de grossesse en raison de l’anatomie complexe du col de l’utérus chez la brebis. Ce facteur peut ainsi fortement entraver l’insémination intra-utérine. Durant le cycle œstral des brebis, la relaxation du col de l’utérus survient à différents niveaux et est principalement régie par les changements du taux d’hormones reproductrices. Cette étude avait pour objectif d’évaluer les effets de l’estradiol et de l’injection intraveineuse (IV) ou intramusculaire (IM) d’ocytocine (à différentes doses), sur l’ouverture du col et le taux de grossesse chez les brebis Zel iraniennes lors de la saison de reproduction. A cet effet, 3 expériences ont été menées sur 120 brebis âgées de 3 à 4 ans et pesant 47 ± 2,5 kg. Dans un premier temps, les brebis ont été reparties équitablement entre deux groupes avant de recevoir chacune 100 à 200 µg d’estradiol. Après 12 heures, chaque groupe a été divisé en 3 groupes de 20 brebis afin d’évaluer l’effet de l’injection IV ou IM d’ocytocine à 3 doses différentes (50, 100 et 150 IU). Le niveau d’ouverture du col de l’utérus a été mesuré avant l’injection ainsi que 15 mn et 12 h après l’injection d’ocytocine. Dans la deuxième expérience, l’effet d’une administration exclusive d’ocytocine sur l’ouverture du col de l’utérus a été évalué. Enfin, pour la troisième expérience, uneméthode de libération contrôlée de médicament (controlled internal drug release ou CIDR) a été utilisée sur 12 jours afin de synchroniser le cycle œstral. Ensuite, les brebis ont reçu 550 IU de gonadotrophine chorionique équine en injection intra-utérine durant la suppression du CIDR. Avant l’IA, les brebis ont été réparties équitablement entre 3 groupes (n=40), un groupe témoin et deux groupes d’essai recevant 100 IU d’ocytocine par injection IM ou IV. Les brebis ont reçu une insémination transcervicale avec une dilution de sperme frais 54 h après la suppression du CIDR. Afin de détecter les grossesses, des ultrasons ont été utilisés 50 jours après insémination les taux d’agnelage et de de naissance gémellaire ont été mesurés après parturition. Les résultats des deux premières expériences montrent que l’injection estradiol n’a pas d’effet sur l’ouverture du col de l’utérus (P>0,05), alors que l’administration de 100 et 150 IU d’ocytocine peut induire la dilatation du col avec ou sans estradiol (P>0,05). De plus, l’administration de 100 IU d’ocytocine (IV ou IM) lors de la troisième expérience, augmente les taux de grossesse et d’agnelage comparativement au groupe témoin (P>0,05). Cependant le taux de naissance gémellaire restait inchangé chez les brebis traitées (P>0,05). En résumé, nos résultats indiquent qu’une injection IV ou IM d’ocytocine peut améliorer le taux de naissance des brebis Zel iraniennes en provoquant la dilatation du canal cervical. L’application de cette méthode est donc recommandée pour augmenter le taux de grossesse des brebis lors de la saison de reproduction.

Keywords [French]

  • Dilation cervicale
  • Estradiol
  • Ocytocine
  • Taux de grossesse
  • insémination artificielle

References

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Archives of Razi Institute
Volume 72, Issue 1
March and April 2017
Pages 33-41

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