Fig. 4
The effect of an intrauterine device (IUD) inserted on day 0 (A) versus IUD inserted on days 5–6 post-ovulation (B) on progesterone (P4) concentration in the blood plasma collected within the time intervals during the estrous cycle: day 0 and day 5 or 6 respectively, and days 10—12, 16- 18, 20—21 from IUD mares compared with control mares (without IUD) with blood samples collected on the same days of the estrous cycle. Asterisks indicate significant differences (*P < 0.05) between IUD mares and control mares (without IUD) at the same time point. Superscript letters indicate significant differences between the control group (control a,b,c) across the time points (days of the estrous cycle) or between IUD mares (IUD.x,y,z) across the time points (days of the estrous cycle)