Levels of the natural hormones 17β-oestradiol and testosterone in serum of cattle: results from population studies in Poland

Introduction: The present study is a comprehensive overview of the natural occurrence of 17β-oestradiol and testosterone in serum of cattle in Poland. Material and Methods: The serum samples (n = 826) were collected from cattle within five years. The samples were examined for the presence of oestradiol and testosterone using ELISA or gas chromatography with mass spectrometry. Results: In 98 samples (24%) 17β-oestradiol was detected above decision limits of applied methods, including five samples over the recommended concentration of 0.1 μg L^-1. Of the serum samples taken from cows (≤18 months of age), 95 and 99 percentiles of the animals had 17β-oestradiol concentration below 0.027 and 0.086 μg L^-1 and of samples from cows over 18 months of age - below 0.059 and 0.125 μg L^-1 respectively. Calculated values for bulls (≤18 months of age) were 0.025 and 0.034 μg L^-1 and for the animals older than 18 months of age - 0.035 and 0.041 μg L^-1. The natural presence of testosterone was detected in 201 serum samples (48.7%). According to the obtained data, 95% and 99% of cows (≤18 months of age) serum samples had testosterone concentration below 0.05 and 0.23 μg L^-1 and the animals over 18 months of age - 0.30 and 0.49 μg L^-1, respectively. For bulls these values did not depend on the age of the animals and were in the ranges of 5 - 6.3 μg L^-1 (95%) and 11.4 - 12.1 μg L^-1 (99%). Conclusion: Our study showed that the threshold values for these hormones in plasma of cattle designated years ago are correct, but they need to be supplemented for animals older than 18 months.