Risk Factors for the Development of Haemorrhagic Anovulatory Follicles in the Mare

Abstract

Haemorrhage into the dominant follicle during the reproductive season is a subtle but definitive cause of infertility in the mare population. This condition however can be of high relevance for an individual in which its incidence is abnormally high. Little is known about the nature and factors affecting the incidence of haemorrhagic anovulatory follicles (HAFs) in the mare. The objectives of the study were to define and characterize the ultrasonographic development and incidence of HAFs and to investigate possible risk factors influencing its occurrence. Detailed reproductive and ultrasound records of seven mares studied during their entire reproductive lives (>10 years and 612 oestrous cycles) were analysed retrospectively and computed into a statistical mixed model. Of all animal studied, two mares were found to have an unusually high incidence of HAFs of approximately 25%. Time of season and use of induction treatments (Cloprostenol) were found to influence its incidence. It appears that early-enhanced stimulatory effect of LH on an ovary with the presence of small and immature follicles might increase the risk of ovulatory failure of those follicles later in the cycle. Mares during the months of highest follicular activity (May to August) and after treatment with hormones to induce oestrus and ovulation are at greater risk to develop HAFs. The potential relevance of this study is two folds: clinical relevance for the practitioner to better understand this condition and so improve reproductive management of mares with abnormally high incidence; and to provide useful insights for researchers willing to further investigate the nature of this phenomenon.

Cloprostenol in Equine Reproductive Practice: Something More Than a Luteolytic Drug

“…1987). The use of PGF has been associated with the formation of haemorrhagic anovulatory follicles in the mare (Cuervo‐Arango and Newcombe 2008; Ginther et al. 2008a).…”

The Effect of Sulpiride Treatment During the Periovulatory Period on Prolactin Concentration and Ovulation in the Mare

“…Subsequently, the mare enters a diestrous-like phase, which lasts the same as in ovulatory mares with corpora lutea [7]. The experimentally induced LUF has been shown to share similar ultrasound and hormonal characteristics with the hemorrhagic anovulatory follicle (HAF) syndrome [8], the most common pathologic anovulatory condition that occurs spontaneously in mares [9,10].…”

Novel use of a double lumen balloon catheter for venous sinus thrombolysis and venoplasty

“…Conflicting reports have also suggested either no association between administration of PGFs and development of a hemorrhagic anovulatory follicle (HAF) [7] or that administration of PGFs in diestrus is associated with an increased risk of development of a HAF [14,18,19]. Development of a HAF was not reported in earlier studies on the effects of PGF administration on subsequent follicular development and ovulation and is not a common observation in our clinical equine reproduction practice.…”