Ovarian follicles in horses are structures within the ovaries that contain the developing oocyte, or egg, and are essential for reproduction. These follicles undergo a series of growth stages, from primordial to preovulatory, influenced by hormonal changes within the mare's reproductive cycle. The development and maturation of ovarian follicles are regulated by hormones such as follicle-stimulating hormone (FSH) and luteinizing hormone (LH). Monitoring follicular development is integral to understanding reproductive physiology and managing breeding in equine practice. This page compiles peer-reviewed research studies and scholarly articles that explore the physiology, development, and clinical management of ovarian follicles in horses.
ROWLANDS IW.Shortly after Cole & Hart [1930] had reported the discovery of a gonadotrophic hormone in the blood of the mare in early pregnancy they [Cole, Howell & Hart, 1931] described the changes that occur in the ovaries throughout gestation, and associated the unusually active condition of the ovaries between the 40th and 150th day with the presence of the gonadotrophin in the blood. During this period the ovaries are very large and contain numerous follicles and a small number of functional corpora lutea. The authors claim that the latter serve initially to supplement the function of the primary corp...
Seidel GE.Principles for selecting future research projects include interests of investigators, fundability, potential applications, ethical considerations, being able to formulate testable hypotheses and choosing the best models, including selection of the most appropriate species. The following 10 areas of assisted reproduction seem especially appropriate for further research: efficacious capacitation of bovine spermatozoa in vitro; improved in vitro bovine oocyte maturation; decreasing variability and increasing efficacy of bovine superovulation; improved fertility of sexed semen; improving equine IV...
Fouché N, Gerber V, Bruckmaier RM, Erni-Wespi B, Zander Y, Vidondo B, Sieme H, Claes A, Kaeser R, Burger D.Anti-Müllerian Hormone (AMH) has been linked to reproductive tract abnormalities in mares and stallions. This study aimed at evaluating AMH as a biomarker for two reproductive conditions in mares. In the first part of this study, plasma AMH was evaluated as an early indicator of the onset of cyclicity in mares in the transitional period from the anovulatory phase during winter anoestrus to the cyclic phase during the breeding season. Ten mares between 8 and 17 years old were included in the experiment which lasted from mid-February until the end of April. Ovarian activity was monitored with u...
Loy RG, Buell JR, Stevenson W, Hamm D.Sixty-two non-cycling mares were classified according to the size of largest follicles at the time of treatment with Prostalene, an analogue of prostaglandin (PG) F-2 alpha. Although oestrus occurred in only 77.4% of mares, 98.4% ovulated at an average of 6.8 days after treatment. Greatest variance of interval to ovulation was observed in mares having follicles greater than or equal to 40 mm at the time of treatment. This was due to regression of large follicles about one-third of the time and later ovulation of a succeeding follicle. This resulted also in greatest uncertainty of prediction of...
Driancourt MA.In this review, the main features of folliculogenesis are summarized and compared among species. In the past few years, ultrasonography has clarified follicle growth patterns, and our understanding of follicle maturation has improved considerably. As the follicles develop towards the ovulatory stage, three features appear to be highly conserved across all species: 1) the sequence of events (recruitment, selection and dominance); 2) the sequential need for gonadotropins (FSH for recruitment, LH for dominance) and 3) the large variability of numerical parameters (number of waves per cycle, numbe...
van Niekerk CH, Morgenthal JC, Sanders CP, Malan JE.Progesterone concentrations were assayed by a competitive protein-binding technique
in peripheral plasma samples collected twice
daily during four oestrous cycles of three
mares, and once a day during the first seven
weeks of pregnancy in four mares. Large
variations were found in progesterone levels
between morning and evening samples on the
same day in the same mare.
The lowest progesterone concentration
was found about the time of ovulation. Within 24 hours after ovulation the progesterone
concentration increased and two peaks, one
at 5 days and another at 8 days, were found.
Be...
Hemberg E, Lundeheim N, Einarsson S.To minimize the number of matings/inseminations, controlled ovulation has been practised since a long time ago. A potent short-term implant, releasing the GnRH analogue deslorelin (Ovuplant((R))) has been used in Australia and North America for several years for hastening the ovulation time in mares, but the product is not registered on the European market. This study was aimed to investigate: (1) ovulation time in mares implanted with Ovuplant when the largest follicle was 42 mm or more in size, (2) repeatability of ovulation time in successive oestruses when treated with Ovuplant, (3) pregna...
