Concentration of testosterone and cholesterol in blood serum of servicing bulls depending on their type of productivity, age and the season

The androgenic hormones are known to control sexualization during prenatal period and to keep up the sex-influenced traits in adult servicing bulls. In particular, the hormones determine functions of testes, prostate, android glands, semen quality, affect the DNA replication, transcription, translation, cell division, they are also involved in immune activity, etc. In turn, production of the androgens is influenced by both internal factors (i.e. genotype, precursors), and external conditions, such as feeding and the season of the year. In our examination conducted in 2012 to 2013, the servicing bulls ( n = 49) up to 30 month old and the older which are used in breeding for milk and meet productivity were tested at different seasons (spring, summer and autumn) to compared the testosterone and cholesterol concentrations in blood serum. In all tested animals an initial content of the hormone and its precursor in blood serum was within the physiological limits. It was shown that the higher cholesterol content, the higher testosterone concentration was tested (Р