Variance
in diameter of the dominant follicle at PGF2a (hour 0) and
at GnRH-2 did not differ between treatments. For circulating
concentrations of estradiol during proestrus (Fig. 2),
there tended (P ¼ 0.07) to be a treatment by time interaction
characterized by similar estradiol concentrations at
hours 0 and 36 with a tendency (P ¼ 0.08) for estradiol
concentrations to be greater at hour 60 in the 5CO than
7CO treatment (no effect of response to GnRH-1, or the
interaction of treatment with response to GnRH-1, was
detected). Peak estradiol concentrations tended (P ¼ 0.06)
to be greater in the 5CO than 7CO treatment and in cows
that responded to GnRH-1 (P < 0.08; Table 1).