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Maitrise de la folliculogenèse chez la chienne a l’aide d’agonistes de la GnRH

Abstract : The mode of action of desloréline implants (Suprelorin®4,7mg, Virbac, Carros, France) allows activation and inhibition of the estrous cycle, with both clinical applications (from estrus induction to chemical sterilization). From a scientific background however, data concerning these different uses were mainly restricted to experimental bitches (Trigg et al. 2001) and yet no clear guidelines concerning the use of this product in females has been edicted. 173 bitches (including 24 experimental beagles) were includes in 6 different experiments to assess the use of these implants from the two perspectives. When used for estrus induction, the implant was administered during anœstrus and removed just after occurrence of ovulation (defined as progesterone level >5-6 ng/mL). All 64 bitches included in these experiments expressed an induced oestrus. For 32 of them, it occurred 4,3±1,4 days [2 to 7 days after] following implant administration. Anovulatory cycles were reported in 14 of these 64 bitches, but no statistical difference could be enlightened to discriminate the ones that ovulated and the ones that did not. When the implant was administered in early anoestrus, 2 out of 22 (9.1%) bitches carried their pregnancy to term while, when implanted in late anoestrus, this concerned 16 out of 23 (69.6%) bitches. Mean litter size obtained was 6.7±3.5 puppies. Luteal failure was suspected in 5 cases: 2 bitches were not pregnant at the time of pregnancy diagnosis and one gave birth 58 days post-ovulation as the owner refused supplementation. The two remaining bitches were supplemented with oral progresterone and gave birth normally. These implants were also used in 109 bitches in the purpose of chemical sterilization. The clinical response was depending of the stage of the cycle. The same features than for oestrus induction were obtained when administering the treatment in anoestrus. Oestrus induction also concerned 3 out of 15 bitches implanted in diestrus. When this was observed, implants were removed, as concomitant high levels of progesterone and estrogens may favored occurrence of uterine disorders. In one of these diestrous bitches, oestrus was induced with progesterone levels >60 ng/mL, which was different from the threshold proposed by Trigg et al (2001), who did not experience oestrus induction when bitches were above 5 ng/mL. In 15 bitches, the induced oestrus lead to side effects that required to stop the treatment: 3 bitches in diestrus, 7 bitches presenting persistent heats which lasts more than 30 days and 5 bitches presenting persistent lactation. Therefore, implanted bitches should be controlled after 30 days to ensure that heats are over and if not, ultrasound examination of the genital tract is advised to rule out the presence of ovarian cysts. Development of medical protocols to avoid the induced oestrus may change this. We tried different strategies to prevent the occurrence of this phenomenon. The use of the aromatase inhibitor anastrozole and the anti-estrogen clomifen did not give satisfying results (3/3 induced oestrus with anastrozole, 5/8 induced oestrus with clomifen). Better results were obtained with the progestagen osaterone acetate: 11 out of 16 bitches did not express induced oestrus, but the phenomenon was not completely prevented. The best results were obtained when implanting prepubertal bitches: none of the 24 animals exhibited oestrus after implant administration. Further data are still required to determine at which frequency the treatment should be administered in order to maintain its effect. However, with one implant administration, bitches, the contraceptive effect lasted less than 180 days in 5 bitches, between 180 and 365 days in 15 bitches and more than 365 days in 19 bitches.
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Submitted on : Tuesday, May 31, 2022 - 5:52:21 PM
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  • HAL Id : tel-03683648, version 1

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Emmanuel Fontaine. Maitrise de la folliculogenèse chez la chienne a l’aide d’agonistes de la GnRH. Génétique animale. AgroParisTech, 2012. Français. ⟨NNT : 2012AGPT0049⟩. ⟨tel-03683648⟩

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