CONICET | Buscador de Institutos y Recursos Humanos

This cytogenetic study was conducted to quantify the incidence and type of chromosomal abnormalities on in vitro-produced bovine embryos. Eight groups of 150 in vitro-matured oocytes were IVF for 18 h. Final sperm concentrations of 1104, 1105, 1106 and 1107 cellsmL 1 selected by the washing method or the swim-up method were utilised. Presumptive zygotes were cultured for 96 h, collected and fixed individually for analysis. Chromosomal complements of 447 embryos were determined by Giemsa staining and direct observation. Rates of haploidy, diploidy, aneuploidy and polyploidy were determined individually. The incidence of chromosomal abnormalities in embryos derived by IVF with 1104, 1105 and 1106 cellsmL 1 did not differ regardless of the sperm preparation method. Polyploidy incidence was strongly increased (Po0.01) at a concentration of 1107 cellsmL 1 in both sperm treatment groups. The fertilization rate obtained with a 1104 cellsmL 1 sperm dose in both selection methods and with a 1105 cellsmL 1 sperm dose with the washing selection method were significantly lower (Po0.05) than those obtained with the other sperm concentrations. The lowest fertilization rates (Po0.05) were achieved with the lowest dose and the washing sperm selection technique. Acceptable fertilization rates with low chromosomal abnormalities can be achieved with a final sperm concentration of 1105 cellsmL 1 or higher regardless of the sperm selection method used. In conclusion, the sperm selection method did not result in differences in the chromosomal abnormality rates on in vitro-produced bovine embryos. The use of high sperm concentration doses produced unacceptable rates of such abnormalities regardless of the sperm selection method. The use of very low sperm doses produced unacceptable fertilization rates, especially when the washing sperm selection method was performed.

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