Fate of follicular ovarian cysts in early postpartum dairy cows treated with PRID/PGF or PRID/PGF plus eCG.

Abstract

To ultrasonographically investigate the effect of administration of exogenous progesterone using a progesterone-releasing intravaginal device (PRID), with or without the addition of equine chorionic gonadotropin (eCG), to cows with cystic ovarian disease (COD) in the first month postpartum. Thirty-three dairy cows (n=11/group) diagnosed with COD between day20 and 30 postpartum were randomly assigned to treatment groups (TG) PRID/PGF and PRID/PGF+eCG or a control group (CG). The CG remained untreated during the 20-day study period, which started on the day the diagnosis was made (day0). Cows of group PRID/PGF received a PRID, which was removed on day10, at which time PGF2α was given intravenously. Cows of the PRID/PGF+eCG group additionally received eCG on day7 intravenously. Ovarian ultrasonography and blood sampling for measurement of plasma progesterone (P4) and estradiol-17β (E2) were done on days 0, 7, 10, 13, and 20 in the TG and on days 0, 10, and 20 in the CG. On day0, all cows had follicular cysts, six of which developed into luteal cysts in the CG. The mean cyst diameter remained unchanged in the CG and decreased in the TG by day20 (p<0.01). All treated cows ovulated and formed at least one corpus luteum (CL) after PRID removal, but only two control cows ovulated (p<0.05). Of 12 ovulatory follicles in the TG dominant on day7, eight formed a CL with a cavity, whereas of 10 ovulatory follicles in the same groups, dominant on day10, only one formed a CL with a cavity (p<0.05). The diameters of follicles, that formed a CL with a cavity, were larger on day10 (p<0.01). Mean P4 concentrations on day0 were ≤1ng/ml in all groups. P4 concentration increased during treatment and decreased below 1ng/ml after PRID removal (p<0.05). Treatment with PRID alone led to resolution of COD in all cows and therefore the additional benefit of eCG could not be critically assessed. CL with a cavity more often originate from larger and older dominant ovulatory follicles.