In vivo oocyte recovery and in vitro embryo production from bovine oocyte donors treated with progestagen, oestradiol and FSH

The effect of treatment of donor cattle with progestagen and oestradiol or FSH on in vivo oocyte recovery and in vitro embryo production was studied. Forty-eight beef x Friesian cows formed eight replicates of six treatments in a 2 (no steroid versus steroid) x 3 (none, single or multiple dose(s) of FSH) factorial design in which follicles were aspirated once weekly for 3 weeks. Oocytes were graded, washed, matured for 20-24 h and then inseminate d with frozen/thawed semen from a single sire followed by coculture on gran ulosa cell monolayers. Treatment with steroid had no significant effect on any follicular, oocyte or embryo production variate other than to reduce the number (P < 0.05) and the diameter of large follicles > 10 mm (P < 0.01) present at aspiration. FSH increased numbers of medium (6-10 mm) and large follicles (P < 0.01) an d there was a corresponding decrease in the number of small follicles (2-5 mm; P < 0.01). The total number of follicles at aspiration increased from 1 7.7 +/- 1.60 for animals not treated with FSH to 23.6 +/- 1.97 following mu ltiple dose treatment with FSH (P < 0.05). Significantly, more follicles we re aspirated following FSH treatment (no FSH 9.7 +/- 1.09, single dose FSH 13.6 +/- 1.30, multipledose FSH 17.3 +/- 1.52; P < 0.05) and numbers of ooc ytes recovered per cow per week increased (no FSH 4.1 +/- 0.76, single dose FSH 5.3 +/- 0.87, multiple dose FSH 5.9 +/- 0.94) but the differences were not significant. Significantly, more good oocytes (Category I) were recove red from animals treated with FSH (P < 0.05). There was no overall signific ant effect of FSH on embryo production rate or the total number of transfer able embryos produced but the number of transferable embryos was highest fo llowing administration of multiple doses of FSH. In conclusion, progestagen plus oestradiol 17 beta treatment did not affect follicle, oocyte and embryo production of oocyte donors aspirated once per week. FSH treatment, however, significantly increased the number of follic les aspirated and Category 1 oocytes recovered. Multiple dose administratio n of FSH resulted in the production of the highest number of transferable e mbryos but this effect was not significant. (C) 2000 Elsevier Science B.V. Ail rights reserved.