In vitro maturation and fertilisation of bovine oocytes in relation to GH gene polymorphism (Leu/Val)

The present study describes the analysis of the associations between the growth hormone gene polymorphism (Leu/Val) and oocyte maturation and in vitro fertilisation in cattle. Two inde- pendent experiments were carried out. In the first one, oocytes were collected from 49 single ovaries, matured in vitro, measured and cytogenetically analysed. One ovary was considered as a donor. The procedure of the donor's genotyping at the GH locus was based on DNA extracted from the granu- losa cells. The GH genotype did not influence the oocyte diameter nor the number of oocytes collected, which were selected for maturation and matured. An unreduced chromosome number was found in 8.8% of the cells at the second metaphase stage and 42.9% of the donors. This anomaly was observed in all genotype groups with a higher frequency in the VV cows ( P < 0.01). In the second experiment, the oocytes collected from 72 single ovaries were matured and fertilised in vitro. The GH genotype of a donor did not influence the number of zygotes cleaved on day-2. It has to be men- tioned, that due to the low frequency of the VV genotype (0.03), the results of the present study should be treated as preliminary and need further analysis.