Some Unusual Conditions of the Uterus

CHAPTER 18Some Unusual Conditions of the Uterus



JOHN P. HURTGEN


A wide variety of conditions may affect the uterus of the mare but occur at a low frequency. Many of these conditions are frequently overlooked, in part because the uterine size and consistency may not be altered and/or the mare’s cyclicity may not be affected. A few of these unusual conditions will be presented, but this list is not exhaustive.



ASYNCHRONY OF ESTROUS BEHAVIOR AND OVARIAN ACTIVITY, WITH ENDOMETRIAL HISTOLOGY


During the transitional phase at the beginning of the breeding season, it is common for mares to exhibit erratic estrous cycles, ovulatory patterns, and estrous behavior not necessarily in synchrony with ovarian activity. This transitional pattern normally becomes quite predictable after one or two estrous cycles. However, each year in private veterinary practice a number of mares appear to be normal in all respects but fail to become pregnant for three or more estrous cycles.


Asynchrony of estrous and ovarian activity with uterine histology, however, has been observed during the natural breeding season (May, June, July, and August). Affected mares have normal estrous cycles and develop normal ovulatory follicles during estrus yet fail to conceive following breeding. The uterine consistency seems normal on rectal evaluation, but the pattern of uterine edema during estrus is less pronounced compared with subsequent cycles. In order to determine the cause of infertility, an endometrial biopsy specimen has been obtained from some of these mares. In general the histologic appearance of the endometrium is suggestive of the anestrous or the early transitional phase of the mare’s reproductive cycle. The luminal epithelium is frequently cuboidal or low columnar, the density of the endometrial glands is reduced, and the endometrial glands are straight, have a small diameter, and appear inactive. Frequently, one or two estrous cycles later, these mares become pregnant or have an endometrial biopsy specimen representative of the breeding season. The uterine consistency seems normal on rectal evaluation, but the pattern of uterine edema during estrus is less pronounced compared with subsequent cycles.


The cause of the asynchrony of the endometrial architecture with ovarian activity is unknown. Hormonal profiles of these mares have not been recorded. Possible explanations may include inappropriate lighting schemes before the breeding season, such as inadequate lighting or constant 24-hours-per-day lighting. Mares that exhibit this syndrome are not likely to repeat this pattern in subsequent breeding seasons. In most cases these mares are identified after three or four cycles have passed, so specific therapy is not initiated. If these mares can be identified before breeding, supplemental estrogen and progesterone may stimulate the endometrium to develop the architecture expected for cyclic mares during the natural breeding season.

Related posts:

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  2. Infectious and Neoplastic Conditions of the Vulva and Perineum
  3. Significance of Bacteria Affecting the Stallion’s Reproductive System
  4. Low-Dose Insemination Techniques

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Jun 4, 2016 | Posted by in EQUINE MEDICINE | Comments Off on Some Unusual Conditions of the Uterus

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