Many people put a lot of time and effort into selecting their mare for
conformation, athletic performance etc. and then matching these to the
chosen stallion’s characteristics. In addition to these, selection for reproductive ability must also be considered. Failure to do so risks wasting significant amounts of money trying to get a mare in foal. By paying attention to a number of factors, many of which you can assess yourself, you can significantly increase the chances of your mare becoming pregnant. If you are the owner of a single mare you will not have a choice of mares to breed from but an understanding of what affects reproductive success will help your decision as to whether or not to breed your mare and may forewarn of problems.

There are a number of reproductive characteristics which can be assessed when considering a mare for breeding. Many of them may not exclude her from breeding but all go towards developing a picture of the mare and her likely chances of being a good broodmare.

One of the first things to consider is the mare’s history. Most reputable owners will have full records of any mare and these should answer questions such as, whether her cycle is regular, she has suffered any infections, been pregnant before, and if so the number of foals, twins, abortions, problem foalings etc. In addition, an answer to questions regarding usual length of her oestrous cycle, when her breeding season normally starts and finishes, whether she demonstrates oestrus better under certain circumstances, will all greatly help in her management. Information should also be obtained on vaccination and worming history, accidents, injuries, operations, whether she suffers from COPD (chronic obstructive pulmonary disease) or EIPH (exercise-induced pulmonary haemorrhage), laminitis, navicular etc. as such conditions may mean she is unsuitable to breed and could be made worse by pregnancy.

It is also worth considering the age of the mare. Mares under five years will be unproven as regards breeding. Mares over twelve years, especially if not bred before, are harder to get in foal due to a higher incidence of infections and objection to the attention of the stallion, and will also give you fewer foals in the remainder of her life than a younger mare. Therefore mares of between five and twelve years are the best, however, you may still obtain a mare outside this range at a good price which will prove very successful.

A mare’s general conformation and condition are important. If a mare is over or under condition this can be corrected by good feeding and exercise but, if a mare is very thin for example, it may be a sign of another underlying problem. A mare’s general confirmation will be considered when selecting for performance, but as far as reproduction is concerned the mare should have a strong back and legs to enable her to carry the extra weight of pregnancy. She should also have a good heart and lung room and plenty of abdominal space. The pelvic area is also important as it contains the birth canal, so this area must be checked for any injury.

Once your mare has passed these criteria you can then turn your attention to her reproductive tract, through external and internal examination. External examination may be carried out by anyone but an internal examination will require a veterinary surgeon. Perineal conformation can be assessed and whether the mare has undergone a Caslick’s vulvoplasty operation. A Caslick’s operation presents problems to a broodmare as the perineal area will need to be cut and re-sutured for each mating and always for foaling. There is a limit to the number of times this operation can be performed and this, in turn, limits the mare’s reproductive life. Ideally, such mares should be avoided. The mammary gland should be inspected for missing teats and obvious areas of damage or injury.

Rectal palpation can be used to give a tactile impression of the reproductive tract. A lubricated arm is inserted into the rectum and the reproductive tract felt through the thin but delicate rectum wall. The uterus and ovaries can be felt in turn and their texture and structures noted. As well as the tone, size and texture of the reproductive tract, the presence of cysts, tumours, stretched broad ligaments, lacerations, endometritis, scars and delayed uterine involution may also be checked for.

Vaginascopy may be used to give a real image of the vagina and cervix. There are many types of vaginascope but generally, they consist of a tube, with a light source at one end, which is inserted into the vagina and illuminates the internal surface of the vagina and cervix. The vaginascope allows the vagina to be viewed directly to assess colour, lacerations, adhesions, tumours etc. The cervix can also be viewed and its appearance should match the stage of the cycle that the mare is in.

The endoscope, a development of the vaginascope, can be used to view through the cervix, higher up the tract, giving a real image of structures. It consists of a series of flexible carbon fibre filaments with a light source and camera attached to one end. One set of carbon fibres allows light from an external light source to pass down the endoscope, the other set transmits the image back to a camera or TV monitor. The endoscope allows the colour of the uterine endometrium, an important indicator of fertility, to be assessed. It should be uniformly pink with no dark patches. Uterine cysts, blood clots, scar tissue, adhesions etc. can be seen and any infections indicated by the presence of cloudy secretions Finally, ultrasonography gives a visual impression of the reproductive tract. This technique is also commonly used to predict ovulation in the mare.

An ultrasonic scanner head is placed in the rectum of the mare and the flat surface directed towards the reproductive tract which lies below. The scanner emits high-frequency sound waves which hit the reproductive tract, where they are either absorbed or ‘bounced back’ to the transducer. Whether they are absorbed or reflected depends on how dense (solid) the structures are that they hit. Dense structures bounce the sound waves back, fluids absorb them. Any sound waves which are ‘bounced back’ are detected by the transducer which in turn transmits them to a monitor where they are translated into an image showing solid structures as white and fluid as black with shades of grey in between. This gives a black and white visual impression of the tract from which abnormalities such as excessive secretions, uterine cysts, tumours, etc. can be detected, along with an assessment of the state and function of the ovaries.

There are other techniques such as uterine biopsy, laparoscopy and
laparotomy which can be used to gain further information about the
mare’s reproductive tract but they are rarely worth the expense and
are mainly used to identify causes of infertility in very valuable mares.

The mare should also be tested for infections of the reproductive tract. The presence of infection may not preclude her from selection but will mean that she must be treated and allowed to recover before covering. Infections are a major cause of infertility and can be detected using swabs which take a sample of the secretions from the uterus, cervix, urethral opening and clitoral area. These are then sent away to specialised laboratories which incubate them under different conditions (aerobic – with oxygen; anaerobic – without oxygen) and on different culture mediums. These will show the presence of any bacteria and their type, i.e. bacteria which cause venereal disease (VD) (transferred at mating). The important VD causing bacteria are Klebsiella pneumonia, Pseudomonas aeroginosa and Taylorella equigenitalis all of which may cause infertility and are passed from stallion to mare and vica versa during mating. There are a number of other bacteria such as: Streptococcus zooepidemicus, Escherichia coli and Staphylococcus aureus which are present in the general environment and so may also pass into the reproductive tract and cause infertility. If any of these are identified, the mare must be treated before she can be bred from and her reproductive tract examined to ensure that it has not been permanently damaged by the infection. Finally, blood samples may be taken to assess red blood cell count, white blood cell count, parasite burden etc. to indicate the mare’s general state of health and well-bein.

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