To understand the differences in steroid hormone contents between goat and cow milk at different lactation stages.

The contents of steroid hormones in goat and cow milk at different lactation stages were investigated using ultra-high liquid chromatography-mass spectrometry (UPLC-MS). Gradient elution was performed using 0.5 mmol/L ammonium fluoride aqueous solution as mobile phase A and methanol as mobile phase B at a flow rate of 0.3 mL/min, and the target analytes were qualitatively and quantitatively detected using an electrospray ionization (ESI) source in the multiple reactions monitoring (MRM) mode.

A total of 11 steroid hormones, 17α-hydroxyprogesterone, 17α-pregnenolone, epi-testosterone, pregnenolone, progesterone, androstenedione, testosterone, estradiol, estrogen, cortisol, and cortisone, were detected from goat and cow milk samples. At the early lactation stage, the contents of 17α-hydroxyprogesterone, estrogen and cortisol showed significant differences between goat and cow milk (P < 0.05), and the contents of progesterone and progesterone showed extremely significant differences (P < 0.01); at the full lactation stage, significant differences in the contents 17α-hydroxyprogesterone, 17α-pregnenolone, androstenedione, and cortisone (P < 0.05), and extremely significant differences in the contents of progesterone and pregnenolone were found (P < 0.01); at the late lactation stage, significant differences in the contents of 17α-hydroxyprogesterone, androstenedione, estrogen, and cortisol (P < 0.05) were observed as well as extremely significant differences in the content of 17α-hydroxypregnenolone, pregnenolone, and progesterone (P < 0.01).

The differences in steroid hormone contents between goat and cow milk may be due to different pregnancy status.