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

Equine Embryo TransferCOMPARISON OF EMBRYO RECOVERY RATES FROMTWO YEARS OLD AND MATURE MARESF. Camillo, I. Vannozzi, A. Rota, S. Romagnoli and G. AriaDipartimento di Clinica Veterinaria, Università di Pisa,56010 San Piero a Grado, Pisa, ItalyINTRODUCTIONEmbryo recovery rates in 2 year old (TY) andmature (MA) Haflinger mares were 74/85 (87%)and 22/26 (84.6%) respectively. No short or longterm effects <strong>of</strong> <strong>the</strong> early use as embryo donors wereobserved in <strong>the</strong> TY mares. This study shows thatTY old mares can be successfully used as embryodonors.Fillies, especially if born during winter orspring, reach puberty at <strong>the</strong> age <strong>of</strong> 12–15 months(Wesson and Gin<strong>the</strong>r 1981), have an ovulatoryseason similar to that <strong>of</strong> <strong>the</strong> mature mares at 2years, but rarely are bred before <strong>the</strong> age <strong>of</strong> 3 years.This is due to <strong>the</strong> concern <strong>of</strong> compromising <strong>the</strong>irbody development and/or agonistic or showperformances. To anticipate by at least one year <strong>the</strong>reproductive life <strong>of</strong> a valuable mare avoiding <strong>the</strong>possible adverse effects <strong>of</strong> an early pregnancy, 2years old fillies could be used as embryo donors.The use <strong>of</strong> 2 year old mares as embryo donorshas been reported to result in a low embryorecovery rates by some authors (Iuliano andSquires 1985; Steiner and Jordan 1988) but not byo<strong>the</strong>rs (Fleury et al. 1989; Savage et al. 1989.)The aim <strong>of</strong> this study was to compare embryorecovery rates from 2 year old and mature mares.MATERIALS AND METHODSDuring May–July <strong>of</strong> different breeding seasonsfifty-one 24–28 months old (2-year-old = TY) and12 4–12-year-old (mature = MA) Haflinger mareswere employed as embryo donors for a total <strong>of</strong> 85and 26 oestrus cycles, respectively.Twenty seven 2- and 3-year-old Haflingermares were employed as embryo recipients.Mares were checked daily by ultrasounds foruterine status and ovarian activity; oestrus wasinduced by prostaglandin F2alfa (PGF 2α ); donormares were naturally bred, or artificiallyinseminated with fresh extended semen, everysecond day <strong>of</strong> <strong>the</strong> oestrus from <strong>the</strong> detection <strong>of</strong> agrowing follicle/s ≥34 mm until ovulation. Tosynchronise ovulations donors and recipients weretreated with human corionic gonadotropin.Seven to 8 days after ovulation, mares wereflushed 3 times for embryo recovery (Lagneaux etal. 1988) ei<strong>the</strong>r with a solution <strong>of</strong> Dulbecco’s PBScontaining 0.2% <strong>of</strong> bovine serum albumin or withsaline, depending if <strong>the</strong> transfer <strong>of</strong> an embryo wasplanned or not. Recovered embryos were evaluatedfor morphology (McKinnon and Squires 1988).When embryo transfer was planned, recoveredembryos were washed 10 times in a new solution<strong>of</strong> DPBS, placed in a French straw and nonsurgically transferred in <strong>the</strong> recipients using aguarded French gun (Lagneaux et al. 1988).Recipient mares, when pregnant, were treatedwith PGF 2α at Day 30 <strong>of</strong> gestation to induceabortion.In <strong>the</strong> following years, foaling rates <strong>of</strong> 11mares previously used as TY embryo donors and <strong>of</strong>8 control mares, <strong>of</strong> <strong>the</strong> same breed, age and studand never used as embryo donors, were compared.These animals were kept on pasture with stallions(one stallion/20 mares or less) and <strong>the</strong> production<strong>of</strong> live foals was recorded for a period <strong>of</strong> 1–8breeding seasons.Statistical analysis was performed using <strong>the</strong> chisquare test.RESULTSNo differences were found in embryo recoveryrates and recipient pregnancy rates in <strong>the</strong> TY and86