Proceedings of the 5th International Symposium on EQUINE ...

Equine Embryo TransferUSE OF BUSERELINE TO INDUCE OVULATION INDONOR MARESJ. F. Bruyas, E. Trocherie, S. Hecht, N. Lepoutre, A. Granchamp des Raux,J.-L.Nicaise, X. Vérin, J. Bertrand, I. Barrier-Battut, F. Fiéni, R. Hoier*,A. Renault † , L. Egron † and D. TainturierDepartment <strong>of</strong> Reproduction, Nantes Veterinary School, B.P. 40706-44307 Nantes cedex 03, France;*Department <strong>of</strong> Clinical Studies, Royal Veterinary and Agricutural University, Frederiksberg, Denmark;† Intervet, BP 17144, 49071 Beaucouzé Cedex, FranceHuman chorionicgonadotropin (hCG) injected iv(2,500 ui) is commonly used for induction <strong>of</strong>ovulation in mares. However, repetitiveadministrations <strong>of</strong> xenogenic gonadotropin inhorses were described as responsible forantibodies production. In France, implantablesustained release deslorelin for ovulationinduction in mares, are not commerciallyavailable. It would be desirable to have ano<strong>the</strong>rmeans <strong>of</strong> inducting <strong>of</strong> ovulation in donor mares.The only one GnRH-analogue available in Francefor animal treatment is busereline. Many previousstudies have shown that a single injection <strong>of</strong> GnRHor GnRH-analogues were not effective in mares.Harrison et al. (1991) suggested that repeatedinjections <strong>of</strong> busereline were able to induceovulation in mares. The purpose <strong>of</strong> <strong>the</strong>se 5 studieswas to test <strong>the</strong> efficacy <strong>of</strong> busereline for hasteningovulation using different protocols in donor mares.MATERIALS AND METHODSFive cross trials were performed to compare, ineach experiment, 2 treatments alternativelyinjected to induce ovulation <strong>of</strong> 2 or 4 successiveoestrous cycles <strong>of</strong> embryo-donor mares (Fig 1). Atotal <strong>of</strong> 22 mares were used. Oestrus was detectedby teasing. Follicular growth and ovulation werechecked by ultrasonography, daily untilobservation <strong>of</strong> 33 mm follicle, <strong>the</strong>n every 12 h(excepted in Experiments 4 and 5) untilobservation <strong>of</strong> a corpus luteum.Tested treatments started when a growingfollicle reached 33 mm <strong>of</strong> diameter.In Experiment 1 and 2, Treatment A(busereline 40 µg) and placebo were injected iv 4times every 12 h. In Experiment 2, blood sampleswere taken every 15 min, until ovulation, formeasurement <strong>of</strong> LH using an homologousradioimmunoassay (Hoier 1994).In Experiment 3, Treatment A (busereline 40µg) and B (busereline 20 µg) were injected iv 4times every 12 h.In Experiment 4, Treatment B (20 µgbusereline injected iv 4 times every 12 h) and hCG(2,500 ui, one iv injection) were compared andtime <strong>of</strong> ovulation was determined by hourlyultrasound examinations between 32 h and 48 hafter <strong>the</strong> first injection or <strong>the</strong> only one <strong>of</strong>treatments.In Experiment 5, treatment C (13.3 µgbusereline injected iv 3 times every 6 h) and hCG(2,500 ui, one iv injection) were compared, andtime <strong>of</strong> ovulation was determined by hourlyultrasound examinations as in Experiment 4.In Experiments 1 and 3, mares wereinseminated with fresh semen from a fertilestallion with a dose <strong>of</strong> 400.10 6 spermatozoadiluted in skim milk extender, every o<strong>the</strong>r day,from <strong>the</strong> start <strong>of</strong> treatment to <strong>the</strong> ovulation. Nonsurgicalembryo collections were performed 6days after ovulation.STATISTICALANALYSISQuantitative data were analysed by Student’s t teston paired series and qualitative data were analysedby <strong>the</strong> method <strong>of</strong> McNemar, each mare being itsown control.RESULTSIn Experiment 1, busereline treatment inducedsignificantly a higher rate <strong>of</strong> ovulation both within76