In vitro and in vivo development of embryos produced by in vitro maturation and in vitro fertilization of cat oocytes.

Cumulus-oocyte complexes of domestic cats were classified by morphology of ooplasm (A = good, B = fair, C = poor) and cultured for 24 h in TCM 199 with gonadotrophins (eCG, FSH, hCG or FSH/hCG). More of type A oocytes (52%) underwent in vitro maturation (IVM) than of type B (41%) or type C (17%). The gonadotrophin source did not affect frequency of IVM of type A (50-53%) or type B (38-44%) oocytes, but IVM of type C oocytes in hCG or FSH/hCG (27%/19%) was about double that in eCG or FSH alone (13%/10%). After IVF, frequency of cleavage for type A (54%), B (41%) and C (26%) oocytes was similar to the IVM frequency of the equivalent type. After 7 days, development to the morula (M) stage in vitro was similar among types (47-58%); however, higher percentages of type A and B oocytes developed to blastocysts (Bl), 31% and 29%, respectively, than of type C (15%). After transfer of day 5 (n = 70) or 6 (n = 32) M and Bl to day 4 or 5 recipients in trial 1 (n = 4) and 2 (n = 3), respectively, the three recipients in trial 2 gave birth to four live kittens. Development in vitro to M of IVM/IVF embryos frozen in propanediol plus sucrose during early cleavage was similar (64-69%) to that of cohort controls (64%), but Bl formation was reduced (13-17% versus 32%). Damage to the zona pellucida after plunging into liquid nitrogen at -30 degrees C was higher (11%) than that of the embryos cooled at 10 degrees C min-1 from -30 degrees C to -150 degrees C before storage (2%).