OBJECTIVETo detect the content of estrogen and progesterone in commercial milk in China and to compare the differences between commercial cows and traditional cows in the content of estrogen and progesterone of the milk, the breeding of cows and the process of milk production.

METHODSEnzyme-linked immunosorbent assay (ELISA) was used to investigate the estrone, estradiol and progesterone in commercial and traditional milk, and literature review and field investigation was used to compare the differences of breeding and milk production.

RESULTSThe mean concentration of estrone, estradiol and progesterone in Mongolian traditional cow milk was (98.5 +/- 12.4) pg/ml, (24.6 +/- 3.0) pg/ml and (0.2 +/- 0.3) ng/ml, respectively. The concentrations of estrone were (150.2 +/- 8.4), (131.3 +/- 16.3) and (128.9 +/- 13.0) pg/ml; The concentrations of estradiol were (35.4 +/- 2.2), (30.3 +/- 3.1) and (30.0 +/- 2.0) pg/ml; The concentrations of progesterone were (20.2 +/- 1.5), (18.1 +/- 2.2) and (16.5 +/- 2.4) ng/ ml, respectively. The content of estrogen and progesterone in commercial milks were higher than that in traditional milks (estrone comparison: t = 5.43, 19.23, 5.89; estradiol comparison: t = 4.14, 4.93, 14.03; progesterone comparison: t = 28.47, 32.73, 22.82; P < 0.05). Mongolian traditional cows did not lactate during the latter half of pregnancy. However, modern commercial cows might lactate almost in an entire period of pregnancy. Moreover, the lactating period was longer and milk production was higher in modern commercial cows than that in traditional cows.

CONCLUSIONSThe content of estrogen and progesterone in commercial milk in Chinese market detected might be higher than that in traditional milk.