Autoimmunity and the endogenous hormone profiles of bull sires

Morpho-functional changes in reproductive organs of bulls due to the influence of continental climate with cold winters and hot summers can repress reproductive function (I.M. Donnik et al., 2005). It requires a deep knowledge of immunobiological, hormonal and biochemical mechanisms regulating the reproductive function in animals, with regard to their adaptability to various environmental and farming conditions (I.M. Donnik et al., 2015). Here, we compared for the first time the autoimmune state of domestic- and foreign-bred Holstein bull sires aged 3 to 9 years ( n = 101) which were housed in two ecologically different regions, the Moscow Province (Head Center for Reproduction of Farm Animals) and the Sverdlov Province (Uralplemcenter, Regional Information and Selection Center). Autoimmunity detected by sperm immobilization test was unidentified in 69 % and 83 % of bull sires from the Sverdlov Region and the Moscow Province, respectively. The percentages of bulls with a high titer (> 1:8) of sperm immobilization comprised 3 % and 8 % in the Sverdlov Region and the Moscow Region, respectively. At the titers of approximately 1:4, the autoimmune anti-sperm state of the animals was reversible and easily restored following recommended technologies during two cycles of spermatogenesis. A comparatively high titer was recorded during more intense exploitation of bulls. The Holstein bulls of different origin also differed in susceptibility to developing the autoimmune anti-sperm response. The sires of the Canadian selection were more susceptible, while the lowest-level autoimmunity was characteristic of the Holland bulls. Endogenous hormone levels correlated with the autoimmunity: in case of the titer elevation, the endogenous hormone concentrations decreased, but unequally, i.e. by 38 % and 46 % for testosterone and estradiol, respectively. The variations in correlation between testosterone and estradiol could reach 49 %. The percentage of animals with the titers of 1:4 to 1:8 was higher among the young bull sires aged 28 months, while the anti-sperm antibodies were not revealed or autoimmunity was weakly expressed in the mature bulls aged 35 months, with the titers of 0 to 1:2. Therefore, the young bulls at the start of their intensive use are more susceptible to various impacts as compared to the pubertal sires.