Chromosomal numeric abnormalities on early bovine embryos derived from in vitro fertilization: effect of the oocyte quality, maturation environment and incubation time

Abstract

Chromosomal aberrations are one of the major causes of embryo failures in the mammals. It is also been demonstrated that the occurrence of this kind of abnormalities is higher on in vitro produced (IVP) embryos. This study was conducted to investigate the effect of oocyte morphology and maturation conditions on chromosomal abnormality rates in bovine preimplantational embryos. To this end, 790 early cattle embryos derived from oocytes with different morphology and maturated in different conditions (maturation period: 24 h vs 36 h; maturation media: five different serum supplements in TCM-199) were cytogenetically evaluated in three sequential experiments. Rates of normal diploidy and abnormal haploidy, polyploidy and aneuploidy were determined in each embryo. Throughout all experiments, the rate of chromosomal abnormalities were significantly (p<0.05) influenced by the oocyte morphology and maturation conditions (maturation time and culture media). We find that a lower morphological quality is connected with high rates of numerical chromosome abnormalities (p<0.05). Moreover, we also find that polyploidy is associated with increased maturation time (p<0.01), whereas maturation media significantly (p<0.05) affected the rates of haploidy and polyploidy. In general, the use of ECS or FCS as serum supplements produced higher rates of chromosomal aberrations (p<0.05) compared to the other serum supplements. According to our results, we can conclude that morphological quality of oocytes and maturation conditions affect the chromosomal abnormality rates of the subsequent IVP cattle embryos.