Infertility and subfertility are among the global challenges of our time. Fertility in livestock farming is not only biologically important, it is also economically important. The aim of this study was to study the effect of these factors on sperm chromatin nucleus and to assess the impact of the fragmentation index degree on bull reproductive performance. The influence of abiotic factors such as ambient temperature, the level of geomagnetic activity and the biotic factorinfectious diseases of male reproductive organs-was studied. At high ambient temperatures (28-30°C), the proportion of sperm with damaged DNA increased by 70% compared to temperatures below 15°C. A Multivariate Analysis Of Variance (MANOVA) confirmed the influence of the geomagnetic activity factor on the degree of nuclear DNA fragmentation in bull sperm cells (level p<0.05). During the summer period, on days with increased geomagnetic activity, the Nuclear DNA fragmentation index in the samples studied was 20.5%. In some of the samples studied, this index exceeded 38% and the coefficient of variation for this index reached 44%. The proportion of sperm cells with abnormal movement also increased during geomagnetic activity. The content of such sperm cells reached 9.1% in bull semen ejaculates obtained during the winter period. More than 12% of sperm had non-progressive movement in summer semen obtained with a K-index ≥5.0, which was 83.8% higher than with a K-index ≤1.0. High geomagnetic activity and temperature and infection of the reproductive organs lead to pathological changes in spermatozoa, an increase in the proportion of spermatozoa with damaged nuclear DNA and a decrease in fertility.

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BackgroundThere are several mechanisms of species isolation and species conservation, one of which is the behavior of individuals during the mating season. Inter specific hybridization is used to create new breeding forms and breeds of farm animals. The aim of this study was to look into the reproductive behavior of males of cultured sheep breeds and their wild relatives during the mating period in order to identify consistent patterns of movements, elementary motor acts, and individual reactions.ResultsIt was found that the duration of the courtship display in the European mouflon was, with a high degree of confidence, longer than in the male domestic sheep. In mouflons, it was 246.5 ± 31.85 minutes, while in rams, it was 88.46 ± 9.23 minutes (p < 0.0001). Many patterns in purebred sheep were shorter, or absent. In wild species, there is a connection between sexual activity and time of day. The highest frequency of intromission in mouflons occurred in the time interval between 6–8 a.m. and 11 p.m.–4 a.m.; in rams, the dependence of sexual activity on the time of day was not observed. During the estrus period, the relationship between females changed. If there were several individuals in the group in the state of estrus at the same time, the dominant females hindered the reproductive success of the lower-ranking sheep.ConclusionsThe present study shows that the patterns of reproductive behavior in males of different species of sheep are similar. However, it was revealed that the species differ in the length of those patterns. A high variability in the strategies of sheep reproduction was observed. For future research, it would be beneficial to focus on the features of the reproductive behavior of female sheep depending on the genotype.