Caslick operation:  Some mares, particularly older mares, have a very ‘tilted’ conformation to the opening to their vagina often as a result of numerous pregnancies & foalings causing a slackening of the perineal and abdominal ligaments and musculature.  This conformation increases the chances of infection (primarily from faeces) getting into the uterus.  The effects of this conformation can be reduced by closing the top half of the vulva.  This operation to stitch the vulval lips is performed under local anaesthesia.  Once the vulval lips have healed together, it is important to remember to “open” the stitched area shortly before the foal is due next season.  This is because she will tear as the foal is born if the caslick is left intact.

Chorulon:  This is a hormone injection, given intravenously, that is used in the same way as Ovuplant to improve the predictability of ovulation.

CIDR:  This stands for Controlled Intravaginal Drug Release- this is a plastic device impregnated with progesterone. Not widely used in the Thoroughbred industry as it is not registered for use in horses but commonly used in cattle breeding programmes, the device is inserted into the vagina and it remains there for 10-12 days and releases progesterone at a constant dose over that time. Similar in theory to the daily administration of regumate but less labour intensive it is gaining popularity in the thoroughbred industry to use on dry mares that are coming into spring transitional oestrus (spring heat). With the withdrawal of the CIDR device the drop in progesterone stimulates or tricks the ovary to develop a follicle and ovulate.

Clitoral swab:  The managers of some busy Thoroughbred stallions require a negative clitoral swab result before they will accept a mare for cover.  A sample is taken of the secretions in a mare’s clitoral fossa and cultured, looking for two particular types of bacteria that can cause reproductive infection in horses if passed to a stallion or other mares.    This swab is taken once during a breeding season.  If a mare has a positive clitoral swab result, local antibiotic treatment is applied until a follow-up swab is negative.  A negative sample is usually required only once in the season, prior to the mare’s first service.

Follicle test:  The mare is examined rectally by ultrasound and palpation to determine whether she is in season and when the best time to mate her will be.  The vet observes the number, size and maturity of follicles on the ovary, and the distinctive appearance of the uterus, to judge if the mare is in season, when she might ovulate and if special uterine treatments are necessary. 

Ovuplant:  An implant that is placed by injection under the mare’s skin containing a hormone that makes the time of ovulation more predictable.  This helps us to predict the ideal time of cover.  It is given when the mare is in season and the maturing follicle reaches a certain size.

Ovulation:  The ovaries of mares contain several follicles which are fluid-filled structures containing an ovum (egg). When a mare is in season one (or sometimes more than one) follicle gradually enlarges until it ruptures (the process of ovulation), releasing the ovum ready for fertilisation by sperm.  Predicting the time of ovulation is of crucial interest to us, because the best chance of conception occurs when the stallion covers the mare immediately before, or as soon as possible after, ovulation.

Oxytocin:  A drug that causes the uterus to contract.  It is most commonly given to mares post-foaling and following service to assist the uterus to eliminate fluid.  It is inexpensive and a very helpful treatment.

Prostaglandin:  An injection designed to bring a mare into season within a few days.  It is only effective when given at a particular stage of the oestrus cycle.

Regumate:  An oral drug which supplements progesterone in the mare.  It is used in some dry mares that are “spring heating” early in the breeding season.  These heats do not result in ovulation .   With a 10 – 12 day course, Regumate stops a spring heat, and the mare will often return to season normally.  It is also used in high doses to treat mares with late pregnancy placentitis, thereby increasing her chance of carrying the pregnancy to term.

Twin reduction:  Some mares (between 10 to 20% of Thoroughbred mares) ovulate more than one follicle during a heat, sometimes many days apart.  This, together with the ability of the sperm of some stallions to be viable for up to 7 days, means that conception of twins is common.  In the horse, twins are essentially a wasted pregnancy because nearly all twins abort before term and those that do survive are usually undersized.  If twins are detected at 14 to 15 days following ovulation one of them can often be “squeezed” (terminated), allowing a healthy full-term single foal.  At 14 – 15 days this manoeuvre is usually successful.  Beyond 15 days, reduction to a single pregnancy becomes much harder and more likely to result in the loss of both foetuses.  The 14 day pregnancy scan is crucial in determining the presence of twins and, ideally, at least one other follow-up scan is often recommended, to improve our confidence that only a single pregnancy is present.

Uterine Cysts:  These cysts are not uncommon in the mare, particularly in mares that have had numerous foals. They are usually fluid filled cysts of the uterine lining and can often mimic early stage pregnancies depending on their size, so it is important that a record of their presence and their location within the uterus is kept. These cysts can range from a few millimetres to several centimetres in diameter. The presence of cysts does not always mean a mare will have trouble conceiving or holding a pregnancy but if there are numerous cysts it is postulated that they can interfere with embryo movement within the uterus and affect maternal recognition of pregnancy.

Uterine endometrial biopsy: A biopsy is taken of the uterine lining whilst the mare is in the crush and the sample is assessed and graded by a pathologist. The changes recorded in the endometrium will correlate to the mare’s ability to carry a pregnancy to term. This procedure is carried out on mares that have repeatedly lost pregnancies post 35 days. Mares with significant endometrial change will still conceive but will not usually be able to carry the foal to term.

Uterine flush: A sterile tube is passed into the uterus and sterile fluid gently flushed in, 1 litre at a time, and then evacuated.  This procedure helps reduce uterine fluid and infection.  It is used post-foaling and, most commonly, following the serving of mares that don’t efficiently clear infection from their uterus.  It is one of the most useful treatments in problem breeders. 

Uterine infusion:  A thin pipette is used to infuse a small volume of medication, usually antibiotic, into the uterus.

Uterine swab: A sample is taken of the secretions within the uterus to culture for bacteria and to check for the presence of inflammation, both of which if present will reduce the mare’s chance of conception.  It is performed at every breeding cycle.  The results of a positive uterine swab are useful to determine the best treatment for mares with infection and/or inflammation of their uterus.