Endogenous hormone level in bull sires in relation to age, autoimmune status, and production performance of maternal ancestors

The role of sex steroid hormones, their physiological functions in the bull sires, and mechanism of action are not still completely elucidated. This paper is the first report of a large-scale survey that we carried out among bull sires under the ecological conditions of Ural region to estimate production of endogenous hormones estradiol and testosterone, and their precursor cholesterol, as depending on the bull age, origin (Denmark, Netherlands, Russia, the USA, France, and Germany), the milk performance of their maternal ancestors, and the titers of anti-sperm antibodies. The relationship between the endogenous hormones and the studied parameters is ascertained, and it is found that the synthesis of steroid sex hormones is sustainable even at low level of blood cholesterol. Our objective was to assay concentration of blood hormones and the titers of anti-sperm antibodies in 56 bull sires including 49 Black-and-White Holsteins and 7 Black-and-White animals of different origin aged from 24 to 91 months which are exploited in the Ural Regional Information and Breeding Center (UralPlemCenter, Sverdlovsk Province, 2016-2017)...