Chromosomal instability of purebred and crossbred dairy cows

Abstract

The article presents the results of research on the karyotype characteristics variability in purebred and crossbred dairy cows. The material for the research was peripheral blood samples of purebred firstborn cows of the Ukrainian red-spotted dairy and Ukrainian black-spotted dairy breeds, as well as crossbred cows obtained from crossing Ukrainian red-spotted with Montbeliard bulls (DG “Nyva” SE of the Institute of Animal Breeding and Genetics named after M. V. Zubets NAAS. Preparation of cytogenetic preparations, analysis of morphology, identification and classification of chromosome aberrations were carried out according to generally accepted methods. We performed cell analysis with the Axiostar plus microscope (Carl Zeiss, Germany) under immersion magnification of 1000 times and took microphotographs. In all studies, the frequency of aberrant metaphases and the spectrum of chromosomal aberrations were determined as parameters of chromosomal instability. The following signs were taken into account: the frequency of aneuploid and polyploid cells, cells with premature separation of the centromeric regions of chromosomes (CRC), cells with structural aberrations of chromosomes (breaks, fragments and associations of non-homologous chromosomes). As a result of the analysis of karyotypes of firstborn cows of purebred and crossbred origin, it was established that the proportion of diploid cells in the norm is on average 85%. The remaining almost 15% are somatic cells with numerical and structural abnormalities. Crossbred cows have significantly higher frequencies (P<0.001) of aneuploid (one and a half times), polyploid (by 27%), structural aberrations of chromosomes (by 20%) than in purebred cows of the Ukrainian red-spotted and black-spotted dairy breeds. 15–20% more cells containing chromosomes with breaks and fragments were also found in crossbred firstborns. The results of the cytogenetic study indicate greater chromosomal instability in crossbred cows compared to purebred cows. One of the reasons for this phenomenon may be the influence of breeding methods, in particular crossbreeding.