Abstract
The influence of sera in culture medium on hatching of equine blastocysts was examined. Non-surgically recovered early blastocysts were cultured for 10 days in TCM199 supplemented with 10% (v/v) of: (1) fetal bovine serum (FBS, n=5), (2) fetal equine serum (FES, n=4), (3) mare serum collected at the day of ovulation (MS-O, n=6), or (4) mare serum collected at day 8 of pregnancy (MS-P, n=5). Mean embryonic diameters at the beginning of culture ranged from 165.3 to 177.3 μm. Embryos in MS-P started to hatch when their mean diameter reached 286.2 μm at day 8.6 of embryonic age. Embryos in MS-O, FES and FBS started to hatch at 322.5μm (day 10.0), 379.3μm (day 8.1) and 405.4μm (day 10.0), respectively. Judged from the maxi-mum diameter of the embryos during the culture period, fetal serum (FES: 1, 556.5μm; FBS: 942.2μm) supported the in vitro development of the embryos better than mare serum (MS-O; 677.5 μm, MS-P; 489.0μm). The hatching manner observed most frequently in FBS and MS-P supplemented media was a prolonged process characterized by either squeezing through a small opening in the zona pellucida or tearing open the zona pellucida. In contrast, a sudden escape from the zona pellucida was found in MS-O (3/5) and FES (2/4). The concentrations of E2 and P4 in FBS, FES, MS-O and MS-P were determined by EIA (E2: 0.074, 9.150, 0.010, and 0.013 ng/ml; P4: 0.800, 8.350, 2.390, and 6.340 ng/ml, respectively). In conclusion, the source of sera for supple-mentation of culture media influenced in vitro development of equine early blastocysts, especially the process of hatching.
