In studies of chromosome instability, the sister chromatid exchange (SCE) test is a particularly sensitive cytogenetic assay for detecting DNA damage. SCE tests of chromosome instability were performed in the group of 6 horse breeds (Pure-bred Arabian, Malapolski horse, Polish noble half-bred, Polish cold-blooded, Hucul and Polish Konik). The chromosome preparations were obtained from our in vitro culture of peripheral blood lymphocytes stained using the FPG technique. The mean number of SCEs/cell in the analysed population of horses was 5.14±1.44. The mean frequency of SCEs in the 6 analysed horse breeds varied depending on the breed. Statistically significant differences were observed between the horse breeds (P<0.01).No statistically significant differences in the number of SCEs per cell were found between the males and females (5.10±1.34 and 5.20±1.52, respectively). The horses were also assessed for the number of SCEs/cell in relation to the age of the animals. The differences between the age groups were statistically significant (P<0.01).

The SCE test is often used as a sensitive and reliable technique in the biomonitoring of genotoxicity of mutagenic and carcinogenic agents. This study analysed the frequency of sister chromatid exchange in domestic horse chromosomes depending on the habitat and age of the analysed horses. The chromosome preparations were obtained from an in vitro culture of peripheral blood lymphocytes stained using the FPG technique. Both the habitat and the age significantly influence SCE frequency. A higher SCE incidence was observed in horses that lived in a large urban agglomeration than in those from the country. Also, a higher SCE incidence was identified in the group of horses above 6 years of age in comparison with the younger ones. Additionally, the frequency of SCEs in the first, second and third chromosomes and the X sex chromosome were analysed in detail. More exposed to the effect of environmental pollutants, the horses from the urban environment developed more double and triple SCEs in comparison with the village horses. The urban horses also developed quadruple SCEs, in addition to the less frequent exchanges.

Cytogenetic tests are highly reliable, sensitive indicators of the early effects of genomic instability. Their results provide information on the organism’s susceptibility to exogenous and endogenous factors and are measures of the degree of repair of DNA damage. Our study assessed spontaneously occurring damage in following four breeds of sheep: Polish Heath, Polish Lowland (Zelazna variety), Polish Blackhead, and Berrichon du Cher. Instability was identified using the following three different tests: a sister chromatid exchange (SCE) assay, identification of fragile sites, and the comet assay. The distribution of instabilities varied depending on the breed. The mean frequency of SCEs was 5.13 ± 1.58, whereas that of fragile sites was 3.30 ± 1.24. The mean level of DNA damage (% head DNA) was 96.52 ± 6.59. The most damage to genetic material was observed in the Berrichon du Cher sheep, and the least in the Polish Heath sheep. The tests used are reliable biomarkers of genome stability in animal breeds, as well as in individuals within breeds.

Constitutive heterochromatin is a highly condensed fraction of chromatin in chromosomes. It is characterized by a high degree of polymorphism. Heterochromatin is located in the centromeric, telomeric, and interstitial parts of chromosomes. We used the CBG ( C: banding using B: arium hydroxide by G: iemsa) staining technique to identify heterochromatin in chromosomes. Analysis of karyotypes of F1 hybrids resulting from intergeneric hybridization of ducks (A. platyrhynchos × C. moschata) and interspecific crosses of geese (A. anser × A. cygnoides) were used to compare the karyotypes of 2 species of duck and 2 species of geese, as well as to compare the hybrids with the parent species. The localization of C-bands and their size were determined. In the duck hybrid, greater amounts of heterochromatin were noted in the homologous chromosomes from the duck A. platyrhynchos than in the chromosomes from the duck C. moschata. In the goose hybrid more heterochromatin was observed in the homologous chromosomes from the goose A. cygnoides than in the chromosomes from the goose A. anser. Comparison of chromosomes from the duck hybrid with chromosomes of the ducks A. platyrhynchos and C. moschata revealed nearly twice as much constitutive heterochromatin in the chromosomes of the hybrid. When chromosomes from the goose hybrid were compared with those of the geese A. anser and A. cygnoides, differences in the average content of heterochromatin were observed on only a few chromosomes.

The study was conducted on spermatozoa of selected farm and free-living animal species, isolated post mortem from the tail of the epididymis, and stained with silver nitrate -AgNO3. The material was collected from pigs, goats, wild boar, and European roe deer. Twenty morphologically normal spermatozoa randomly selected from each animal and well visible under the microscope, were analysed. The following measurements were considered: head length, width, perimeter and area, acrosome area, mid-piece length, tail length, and overall sperm length. AgNO3 staining differentiated the acrosomal (light hue) and distal (dark hue) part of the sperm head, and a light-hued mid-piece was visible within the sperm tail. Silver nitrate staining revealed species and variety-related differences, particularly in reference to the sperm head. Clear-cut differentiation within the head and tail area made it possible to perform detailed morphometric measurements of the spermatozoa.