205. The effect of FSH concentration during IVM and gamete co-incubation length during IVF on the development of unstimulated prepubertal ewe oocytes

Abstract

The developmental competence of prepubertal oocytes can be increased by the administration of gonadotrophins prior to oocyte collection (1); but this is not possible with abattoir-sourced oocytes, and modifications to the IVP system may increase in vitro development. Experiments were conducted to determine the effects of FSH concentration (10, 20 or 60 μg mL^-1) during IVM (5 replicates) and gamete co-incubation length (short: 2-3 h, long: 18-20 h) during IVF (6 replicates) on subsequent embryonic development. For both experiments ovaries were collected from prepubertal lambs (16-24 weeks) slaughtered at an abattoir and embryos produced in vitro (1). Data were analysed by chi-squared test. Oocyte cleavage at 48 hours post-insemination (hpi) was higher for oocytes matured in medium containing 20 (60/77; 77.9%) and 60 (56/73; 76.7%) than 10 μg mL^-1 (40/67; 59.7%) FSH. Blastocyst formation (% cultured oocytes) on Day 7 (Day 0 = IVF) was higher for oocytes matured with 20 (31/77; 40.3%) than 10 (16/67; 23.9%) or 60 μg mL^-1 (20/73; 27.4%). Oocyte cleavage at 48 hpi was reduced for short (36/57; 63.2%) compared with long (49/55; 89.1%) co-incubation, although blastocyst formation (% cultured oocytes; Day 7) did not differ between groups (22/57; 38.6% and 23/55; 41.8%, respectively). These results demonstrate that increasing the FSH concentration above normal levels during IVM of prepubertal lamb oocytes improves development in vitro. Gamete co-incubation length did not influence the proportion of oocytes progressing to the blastocyst stage.

(1) Morton et al. (2003) Proc. Soc. Reprod. Fert. P18.