Asynchronous embryo transfer in rabbits

THERIOGENOLOGY ASYNCHRONaUS EMBKYD TKANSFEK IN KABB1l.S X. Yang, M. Simkin, M. Battista, 6. Wilcox and K.H. Foote Department of Animal Science Cornell University Ithaca, New York 14853 Previously we reported (Theriogenology, 23:239. 1985) that there was no difference when 3.5-, 4.0- and 4.5- day embryos were In order to extend the degree of transferred to day 4 recipients. asynchrony with possible implications for manipulating embryonic components in embryo engineering studies, experiments were performed using day 3 and day 4 recipients receiving embryos which were 21 day asynchronous, compared to a synchronous control. Forty-four donor and 54 recipient Dutch-belted rabbits were used. Donors were superovulated by a standard FSH and LH procedure with insemination at the time of LH injection (day 0). Embryos were collected on day 2 from the oviduct and on days 3, 4 and 5 from the uterus. The flushing medium was phosphate-buffered saline containing glucose, pyruvate and bovine serum albumin. Recipients were ovulated via an i.m. injection of 1.2 ug of gonadotropin releasing hormone analog (Buserelin, Hoechst) 3 or 4 days before surgery. Embryos of the same age from several donors were pooled for transfer. Survivors in preg. does Donors Recipients Days Days Number

No. of embryos trans -ferred

2 3

3 3

10 1

80 8

3 4 4 5

4 3 4 4

13 11 14 5

128 88 144 40

d/Including

Pregnancies at: Day 12 Term 10 48:

No. of Term embryos in Day 12 pregnant ~ recipients No.(%) No. (X) 32 8

8 7 2 0

101 64 z

13(31) 6(75) 5Oi50) ::123:; 51(63) 6(7) 6(18.8) O(0)

resorbing fetuses.

Day 2 embryos were transferred to the oviducts of 10 day 3 recipients and 4 became pregnant. All other transfers were to the uterus. Survivors to term in pregnant does for day 4 embryos to day 3 recipients were not significantly (P>.O5) lower (17/64) than day 2 embryos to day 3 recipients (13/32). Day 3 embryo survival in day 4 recipients was not significantly lower (P>.O5) than synchronous transfers, but there was an unexpected loss following laparotomy. None of the day 5 embryos survived to term. Thus, it appears that +l day asynchrony between donors and day 3 and day 4 recipients Tn rabbits is compatible with successful transfer, but day 5 embryos are difficult to transfer and may be damaged by handling. (C. Kim, P. Im and X. Zheng helped with the surgery).

JANUARY

1986 VOL. 25 NO. 1

219