The relationship between the concentrations of estradiol and progesterone in commercial whole milk and seasons alternation.

Seventy two samples from three brands(A,B and C) of commercial whole milk were investigated in a year.A sample in a lot number was collected from every brand once every half a month.Total estradiol(TE2) and progesterone(P4) in whey were assayed by immunochemiluminometric assays to observe the relationship between TE2 or P4 in commercial whole milk and seasons alternation.The results showed that: P4 concentrations in brand B and C at the first stage(from Spring Equinox to early Autumn) were respectively higher than those at the second stage(from early Autumn to Spring Equinox in the next year)(P0.05 in both).At the second stage,P4 concentration in the brand A was higher than that in the brand C(P0.05).P4 concentration for the all of the lot numbers of 3 brands at the first stage was higher than that at the second stage(P=0.001),and no statistically significant difference in TE2 was found between the two stages.At the first stage,median for TE2 among lot numbers about brand A,B and C were respectively 168,180 and 180 pg·mL(-1),and for P4 were respectively 1.76,1.85 and 1.38 ng·mL(-1).At the second stage,median for TE2 among lot numbers about brand A,B and C were respectively 180,160 and 160 pg·mL(-1),and for P4 were respectively 1.55,0.95 and 0.76 ng·mL(-1).Median for TE2 and P4 in all lot numbers at the first stage were respectively 176 pg·mL(-1) and 1.57 ng·mL(-1),and at the second stage were respectively 164 pg·mL(-1) and 1.13 ng·mL(-1).Median for TE2 and P4 in all lot numbers in a year were respectively 172 pg·mL(-1) and 1.46 ng·mL(-1).It was concluded that there were significant differences in P4 of milk whey among the same brands as well as different brands,and P4 of milk whey from Spring Equinox to early Autumn was higher than that in other period in a year,and there was also fluctuation in TE2 of milk whey among lot numbers.