CHROMOSOMAL ABNORMALITIES AT EARLY STAGES OF DEVELOPMENT IN ZEBU EMBRYOS PRODUCED IN VITRO

Bovine embryos produced in vitro (IVF) have a high incidence of chromosomal anomalies. However, such occurrence still was not determined in zebu embryos. The aim of the present study was to evaluate the frequency of chromosomal alterations of IVF zebu embryos. It was used IVF embryos of 2; 4; 8; 16 cells and compacted morulae derived from oocytes collected from ovaries of slaughtered Nelore cows. Morulae recovered from superovulated Nelore cows (IVP) were used as control. Embryonic cells were submitted to conventional procedures (Giemsa staining) and karyotype reading with an optical microscope. Differences between normal and abnormal karyotype was established using.2 test. It was found chromosomal anomalies in 29.9% (32/107) of IVF embryos and 13.0% (3/23) of IVP embryos (P> 0.05). Also, incidence of chromosomal anomalies was not influenced by the stage of development of IVF embryos. Mixoploidy and polyploidy were the only chromosomal anomalies present in both, IVF and IVP embryos. From IVF embryos that showed chromosomal anomalies, 40.6% and 59.4% were male and female embryos, respectively (P> 0.05). It was concluded that about one third IVF zebu embryos at early stages of development present chromosomal anomalies and their incidence is not related to a specific period of embryonic development.