V I a B I L I T Y of Stored Equine Embryos 1

Equine embryos were recovered nonsurgically 6.5 d after ovulation (Exp. 1) and those >200 tim were stored in one of three media: 1) Ham's F10 + 10% fetal calf serum (FCS) under 5% CO 2 , 5% O~and 90% No at 24 C (Ham's F10); 2) Minimal Essential Medium with Hank's balanced salts + 10% FCS in air (MEM) at 24 C or 3) MEM at 5 C n=lO/treatment). Embryos 4200/~m (n=10) were bisected microsurgically; one-half of each embryo was stored in Ham's FIO and the other half in either Dulbecco's phosphate-buffered saline + 10% FCS in air at 24 C (DPBS), or MEM in air at 24 C. At O, 12 and 24 h, embryos were: 1) measured; 2) assigned a developmental score of 1 to 4 (l=tight morula, 4=expanding blastocyst) and 3) assigned a quality score of 1 to 5 (l=excetlent, 5=degenerate). Whole embryos stored in MEM at 5 C or 24 C did not (P>.05) advance in development by 24 h, whereas those stored in Ham's FIO at 24 C were more (P<.05) advanced (i.e., higher developmental score) by 24 h. From 0 to 24 h, 1 of 10, 6 of 10 and 7 of 10 whole embryos developed when stored in MEM 5 C, MEM 24 C and Ham's FIO 24 C, respectively. Embryo quality was better at 24 h (P<.05) for embryos stored in Ham's F10 at 24 C compared with MEM at 5 C. Quality of bisected embryos was better (P<.05) for those stored in Ham's FIO compared with MEM or DPBS. Experiment 2 evaluated the viability of embryos stored in Ham's F10 at 5, 24 or 37 C for 12 h and 37 C for an additional 12 h (n=lO/treatment). Embryos cultured at 5 or 24C did not (P<.05) develop or grow during the initial 12 h, but upon culture at 37 C they advanced (P<.05) in development. Experiment 3 was designed to determine pregnancy rates for embryos transferred nonsurgically after storage in Ham's F10 at 24 C for r h or 12 h. Treatments were: 1) embryos transferred ~1 h into recipients that ovulated 1 d prior (+1) to 3 d after ( -3) the donor mare; 2) transferred ~<1 h into progestin-treated recipients; 3) transferred after 12 h into naturally synchronized recipients (+1 to -3 d in relation to donor) and 4) transferred after 12 h into progestin-treated recipients. Progestin-treated recipients were administered .044 mg of ahrenogest/kg body weight daily beginning the day after the donor ovulated. Thirteen of 32 synchronized recipients became pregnant (d 30) compared with 0 of 17 for progestin-treated recipients (P<.05). Pregnancy rates for embryos stored for 12 h were nearly identical (P>.05)to those transferred in ~<1 h. Therefore, embryo viability was maintained for 12 h by storage in Ham's FIO at 24 C. (