Effect of ovarian cystic or haemorrhagic follicles on embryo recovery and survival after transfer in hCG-ovulated rabbits.

The relationship between the presence of cystic and/or haemorrhagic follicles in both donor and recipient does and survival at birth of frozen-thawed embryos (778 embryos transferred) from 3 selected rabbit strains (NZ: New Zealand white; SY and SB: synthetic breeds) were studied. Donor does (SY:108; NZ:99; SB:96) were mated and treated with 25 IU of hCG. Only morphologically normal oviductal morulae (64-66 h) were frozen. Frozen-thawed embryos from each of the 90 donor does were transferred into the oviducts of synchronized recipient does of the same strain 48 h after injection of 25 IU of hCG (SY:31; NZ:28; SB:31). The frequency of follicular anomalies (36 and 43%) was high in both donor and recipient does, respectively, and it was not affected by strain or parity. The follicular anomalies had a negative effect on the percentage of embryos recovered in the oviduct (70 vs 77%) but not on the percentage of recovered embryos catalogued as morphologically normal (97%). The absence of follicular anomalies in recipient does had a significantly favourable effect on the pregnancy rate (63 vs 18%; P less than 0.05) and consequently on embryo survival rate at birth (26 vs 7%; P less than 0.01).