Abstract:

Six commercial brands (A, B, C, D, E and F) of whole milk produced in Wuxi city or other regions from February to April were sampled two batches every month to obtain 36 samples. A survey of estradiol (E2) and progesterone (P4) contents in the whole milk samples measured by immuunochemiluminpmetric assay was carried out in this study. The content of progesterone present in whey obtained from whole milk by centrifugation was directly measured. Before estradiol measurement, whole milk was required to be hydrolyzed with sulfatase. Results showed that no statistic difference in TE2 content (a quarter of E2 content) was observed among 6 commercial brands of whole milk surveyed in this study. Brand F exhibited a higher P4 content than brand C (P＜0.05), while other brands do not differ statistically in P4 content. Among 36 whole milk samples, the maximum value of TE2 content was 2.32 higher than the minimum value and the ratio of maximum to minimum P4 contents was 6.67. For brands A, B, C, D, E and F, the ratio of maximum to minimum TE2 contents were 1.38, 1.60, 1.82, 1.79, 2.17 and 1.68, and the ratio of maximum to minimum P4 contents 3.19, 5.98, 2.89, 1.38, 1.86 and 1.67, respectively. The ratios of maximum average to minimum average values of TE2 and P4 contents among 6 brands were 1.25 and 3.05, respectively. The above results indicate that 6 commercial brands of whole milk significantly differ in P4 content, and there is a wide fluctuation range of P4 content in different bitches of the same brand. Moreover, some difference in TE2 content is also found in different bitches of the same brand.

Key words: milk, whey, estradiol, progesterone, immunochemiluminometric assay