Mare's Ovulation Control by
Vaginal Mucus Analysis

(extract from DMV Iancu MORAR'S thesis on Equine reproduction. Teacher at the university of CLUJ ROMANIA)

It is well-known that the estrus period is dominated endocrinally by estrogen hormones. Produced by the internal sheath of the mature graafian follicle, the estrogen acts on the whole body, from the central nervous system to the gonads. The receptors of the estrogen are situated intercytoplasmically and internuclearly. The target tissues of these hormones are the vagina, the cervix, the uterus, the oviduct, the ovaries, the mammary glands, the hypothalamus, the hypophysis, the brain, the suprarenal glands, and the liver.

They act on the genital system by proliferation, secretive, hypertrophic, congestive, and hyperplasia processes stimulating the proliferation of granular cells. Also they cause the increase of the mitotic index and stimulate the accumulation processes of the specific nutrient substances. At the same time, the estrogen influences the change in the physical and chemical characteristics of the cervico-vaginal mucus which is noted in all species.

Purpose of study

In this study we intend to evaluate a new method of detecting the precise moment of ovulation. This method is proposed by a team of American researchers and it is designed especially for the mare. The method is based on the analysis of the vaginal mucus modifications as a result of the variation of estrogen during the period of estrus.

Resources and methodology

The research was conducted between June 15 and July 15 1997 on a group of 11 mares of different races (Semiheavy, Lipizzan and Furioso North-Star) between 5 and 15 years old and from studs owned by the State or private farms.

The mares were examined vaginally at the beginning of clinically measurable heat. Then they were subject to a scan every day before ovulation. After ovulation the examinations were repeated every 48 hours for 10 days.

The OVATEC operating principle is based on the researchers' results on reproduction physiology studies which state clearly the presence of well-defined modifications at a vaginal level (mucus and secretions) in healthy females during ovulatory heat.

The modifications noticed in the vagina are analyzed by a computer situated at the end of the probe, and the information is displayed on a screen as figures. The regular use of probes during the estrus will result in the display of certain figures on the digital box screen. When the figures are displayed on a graph, they will identify a heat model that indicates the optimum moment for insemination of the mare.

Apparatus Description

Picture 1. OVATEC Components

OVATEC (picture 1) consists of the following:

• vaginal probe, consisting of the cervical sensor (A), steel rod (B) and probe handle (c);

• connecting cable (D), provided with two couplings, one for the probe and one for the digital box;

• digital box (E) containing an electronic control device, a control panel and a display screen. The digital box is provided with a mounting belt.

The operating system of this device should be followed systematically. The correctness of the interpretation of results depends on the following steps:

1. Mounting the cable that connects the probe to the digital box, by connecting the two couplings at both ends.

2. Testing the operating capacity of the device. After the device is activated by turning on the ON/OFF switch on the right of the screen, the probe is introduced in the bottle with testing liquid that must be at room temperature. Temperatures less than 25°C can result in measuring errors. 100 or less should be displayed on the screen. A value more than 100 indicates the oxidation of the probe which requires a deoxidization. The deoxidization is done by thoroughly cleaning the probe with Ajax powder (exclusively).

   The switch on the left side on the frontal side of the digital box (RUN-HOLD) is designed to remember the last figure marked down before starting a new test. If we the 2 switches are pushed down simultaneously and the probe is not in the vagina, the screen should display 0.

3. Sterilizing the probe. Use "HIBITAN" solution in order to sterilize the probe. After the probe is thoroughly cleaned with this solution, a diluted solution of "HIBITAN IRIGATION" (3ml/l water) prepared in the plastic tube provided with the apparatus is used to sterilize it for at least 30 seconds.

4. Washing the probe. Clean warm water at 45°C is used to thoroughly rinse the probe. It is necessary to rinse the probe as the HIBITAN solution is spermicide and irritating to the vaginal mucous membrane.

5. Preparing the animal. This step consists of restraining the mare that is to be examined by placing it in a special stand or by fastening the posterior legs as is done for covering. Clean area of the anus and vulva with soap and water and dry with a clean towel.

6. Introducing the probe. After washing and drying the vulva, part the lips and insert the probe so that the sensor doesn't touch the lips and so that no air enter the vagina. The insertion of the probe is at an angle of 45° on a length of 10-12 cm after which the rod takes a horizontal position continuing the insertion until the sensor reaches the cervix. Then, pull it back 2 cm and we start the simulation, keeping the probe in the vagina.

7. The stimulation is done by moving the probe back and forth and in circles for an optimum coverage of the sensor with mucus. The movements will last 30-45 seconds, and then stop. It is important to keep the probe in contact with the cervix and with the vaginal walls until the value displayed on the screen is stable.

8. The display on the screen read after the figure is stable by pressing the "run-hold" switch on the left of the screen.

9. Pulling out the probe. After each measurement, the probe is inserted in the HIBITAN solution for sterilization for at least 30 seconds, until the next mare is prepared. In the end the probe is disinfected, rinsed and dried.

The OVATEC examinations are doubled by scan examinations of the ovaries to see if there is a correlation between the figure indicated on the screen and the ovarian activity.

The method used for scanning is shown in the preceding chapters and is used for each mare after the vaginal examination. The mares indicating follicles on the ovaries more than 35 mm in diameter were inseminated at 48 hours intervals, no matter the results of the vaginal examinations.

Results and Discussion

Repeated examination of the 11 mares resulted in the following 3 groupings by ovulation criteria:

• group 1, the 5 mares who showed normal single ovulation scan-diagnosed by the disappearance of the follicle and appearance of the haemorragic body;

• group 2, the 2 mares who were diagnosed with double ovulation;

• group 3, the 3 mares who were diagnosed with no ovulation, the follicles regressing spontaneously at different intervals.

1. Mares with normal ovulation

The results of the vaginal and follicular measurements for the mares of the first group are shown in Table no. 1. On the basis of these results graphs are drawn in order to derive a model for each method (picture 1 and 2).

OVATEC model
OVATEC measurement
Control
Ovulations

Table with results from group 1.

The picture below (picture 3) is a graph of the measurements made on the 5 mares whose ovulation was diagnosed by scanning. When the graph above (picture 2) is correlated with the scan measurements of picture no. 2 the relationship between the two methods is clearly noticed.

For all 5 mares examined the display of the OVATEC measurements is in the shape of the letter V. The maximal values (200-250) are registered 2-3 days before ovulation and 3-4 days after ovulation, and the minimal value displayed on the OVATEC screen ranged between 80-105 (picture 1)

SCAN MODEL
Diameter in mm
Control
Ovulations

The ovulation measured in the scan took place 0-24 hours after the OVATEC measurement indicated the minimal value.

2. Mares with double ovulation (2 mares) are represented in the table below:

The 10 daily examinations of these mares showed a successive double ovulation at about 72 to 96 hours apart. The 2 ovulations are diagnosed by the vaginal examination performed by OVATEC and confirmed by same day scan.

The graphs of these situations are represented as follows:

Double ovulation scan graph
Diameter in mm
Control
Case 1
Case 2

Double ovulation OVATEC graph OVATEC measurement
control
Ovulations

The double ovulation cases were diagnosed by both methods. The results of the measurements are included in graphs in order to depict their complete growth (pictures 4, 5). The scan measurements graph depicts a continuous increase, while the second ovulation is marked by a new growth similar to the first, at the end of which the ovulation takes place.

Results from the registration of the OVATEC measurements indicate a broken line with a first descending portion with minimal values up to 80-95, followed by a rise to values of 160-170 and another descending line . The smallest values of the second descent are 85-90. The secondary ascending branch is followed until it reaches values of 180-200. The OVATEC measurements graph also contains the registration of the ovulations detected by scanning. The ovulation was diagnosed in all cases after reaching the minimal values measured by OVATEC after 0-24 hours.

3. The group of mares who were in heat without having an ovulation (table 3) consisted of 3 mares.

The scan examinations of the ovaries demonstrated a continuous follicular growth up to 35-36 mm, but no ovulation. On the contrary, the follicle had a tendency to regress. The heat was prolonged and without ovulation.

As a result of the graphic representation of the measurements the following graphs were obtained (pictures 6, 7):

Scan measurements graph diameter in mm
control

The diameter of the biggest follicle did not exceed 35-36 mm in any of the three analyzed cases, and the follicular growth speed was very slow. No ovulation was detected during 10 examinations and no luteal structure was indicated.

OVATEC graph
OVATEC measurement
control

Analysis of the graph in picture 7 reveals a specific characteristic of this model - "saw teeth". The minimal values do not go under 150, and the maximal ones slightly exceed 200. Successive readings do not show a clear descending tendency as in the case of mares who had an ovulation.

The correlation of OVATEC measurements with the simultaneous scan of the biggest follicle diameter shows clearly the relationship of the two methods and it supports the use of the apparatus to obtain the best results in horses' reproduction.

Modifications of the organoleptic, physical and chemical characteristics of the cervico-vaginal mucus are important and to a certain extent detectable by examination. The fact that the mare is in heat longer and that the acceptance of the stallion also takes a lot of time, determines that the preliminary examination followed by the full clinical examination, in most of cases, is not enough to set the ovulation date. Complementary methods, such as those based on the modifications of the vagina and cervix, are efficient and useful in the mare's reproduction management.

The situations described above, although based on few cases, at least are enough to show that this technique can detect the modifications of the composition and/or structure during mare's estrus, especially close to ovulation. This opens up real possibilities for the study of the technique and the extension of its uses.

Summary

The comparative analysis of the two diagnostic methods in equine gynecology indicates a close relationship between the results of the simultaneous scan and vaginal examinations. Thus, it is concluded that:

• OVATEC is a simple, fast and efficient method of exploring mare's genital functions;

• OVATEC allows for the precise setting of the moment of ovulation as indicated by the V-shaped graph;

• OVATEC allows for the detection of the appearance of a double ovulation as indicated by the W-shaped graph;

• when the display is a saw tooth-shaped broken line and it keeps its shape for a longtime, the mares are in heat without ovulating.

Practical advice

• the repeated probe examinations of mares with OVATEC can offer more information about the state and health of their genital system;

• the use of this diagnostic technique will further reduce the number of coverings;

• the prevention of twin gestations, undesired in horses by diagnosing the first ovulation and avoiding the covering in the case of double ovulation.