Persistent anovulatory follicles in the mare

Abstract

In this study the hormonal levels in the follicular fluid of a group of mares (n=20) with persistent anovulatory follicles were compared to a control group (n=11) of mares with normal preovulatory follicles. Follicular fluid was collected following transabdominal puncture of the follicles or transvaginally with the aid of ultrasound for hormone measurement. Of the mares with persistent anovulatory follicles, 72% of the cases occurred in March and April and only 28% of the punctures were carried out in May, June and July. The persistent follicles showed echogenic particles in the follicular lumen on ultrasound in 71.4% of all cases. The concentrations of oestradiol, progesterone and inhibin B were significantly lower in the follicular fluid of the anovulatory group as compared to the controls. The concentration of oestradiol was positively correlated with that of inhibin in the follicular fluid of the anovulatory group, whereas in the control group there was a negative correlation between inhibin and progesterone. Of the hormones in peripheral plasma, testosterone was significantly higher in patients as compared to controls (0.02 vs. 0.01 ng/ml, p<0.05); other hormone concentrations were similar in both groups. The lower concentrations of oestradiol, inhibin, and progesterone in the follicular fluid of the anovulatory group suggest an impairment of granulosa cell function in this condition. Puncture of the persistent follicles is a suitable treatment for affected mares resulting in a normal oestrous cycle.