Age dynamics of hormonal level in heifers under different breeding technology

To study age dynamics of cortisol, triiodothyronine, thyroxine, oestradiol and progesterone levels, the parameters were tested in the Black-and-White heifers of different ages (from birth to 18 months) kept in an industrial environment and at private farms. The cattle from private farms was characterized by earlier onset of pubertal hormonal activity of the ovaries in comparison with commercial animals. Cortisol levels were higher in heifers from commercial facilities as compared to those of private farms indicating more stressful conditions for them. Our study demonstrated that breeding technology has a great importance for development of the endocrine system and perhaps for future productivity and fertility in cattle.