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THE CASLICK: A Stitch In Time Saves...

Prior to reading this feature, I suggest you read my article: The Sexual Tract 

Talking about the vulva might sound a bit tacky to the uninitiated, but maintaining good managerial practice by looking after the mares’ fanny is very important as it has a profound effect on her fertility. The caslick is an integral tool to achieve this objective, and is the most common surgery performed on the female equine (castration being the most common in the male equine!). Indeed, by the end of a broodmare’s breeding career, nearly all will have a caslick.

The job of the perineum, vulva, and the cervix
Attention soldier! … Protect the uterus at all costs from bacterial or infectious invasion! The perineal region holds the front line together, commanding the vulva to stand straight and tight. The first line of defence has two regiments working together, the vulvae constrictor muscle wards off the enemy at the fore, and not far behind, the vestibular constrictor muscle will perform the same duties as a back up. Should the enemy breach the dual front line defence and reach the higher ground of the vestibule, it’s up to the cervix to ensure only friendlies enter the uterus upon invitation. If the Calvary fails, then it’s time rebuild the fort walls as the long term and ultimate defence of an injured and aging army: The Caslick Operation!

Indications for a Caslick

The below indications will result in the primary cause of infection: i.e. air being sucked into the reproductive tract and even faecal matter could be a contaminant.
Sloped Vulva: When the mare’s vulva is sloped beyond approximately 10 degrees from vertical, then it is an indication that the whole sexual tract is becoming compromised with reliable fertility at risk: the greater the tilt of the vulva, the lower the chances of conception and maintaining pregnancy. For more extreme cases, other surgical procedures may need consideration.
Poor vulva seal: the vulva may look straight enough, but air being pulled in indicates that the seal is not effective. This may be due to the vulvae constrictor or vestibule constrictor muscle loss of elasticity with time, or from injury. Race fillies can be heard to draw in air due to the action of galloping and body shape. These fillies will get a caslick during their racing career, but with maturity and lifestyle change, this may not need to be continued.
Hear sucking in air vaginally: During deep estrus (in season) the mare’s reproductive tract will relax somewhat. Some mare will be heard to wind suck vaginally during this period, and could indicate it is time to think about a caslick.
Damaged or poor cervical seal: the cervix can suffer wear and tear from irritation, mild non surgical injury and, repetitive physical assault from foaling, serving and veterinary procedures such as flushing. The caslick may help reduce the level of assault.
Infertility for no apparent reason: when infectious contamination is ruled out (by uterine swab) and uterine endometrium is still sound (uterine biopsy results are clear), yet the mare is still not going in foal, a good option to cover all bases it to stitch her up. Often the tables will turn and the mare becomes pregnant.
Repetitive infection presence in the uterus despite treatment: For a myriad of reasons the mare might keep returning indications of uterine infection and/or inflammation and her vulva appears straight, so it is worth eliminating pneumovagina and caslick her.
A previously caslicked mare: The caslick operation was done for a reason. Should this caslick be opened for whatever reason, it should be reinstated after foaling or serving.

The Caslick Operation
The Caslick operation is the method of stitching the mare’s vulva lips together. The intended surgical site starts at the upper part of the vulvae lips (labia) just under the anus and will extend to the pelvic brim. Local anaesthetic is used in the process, injecting under the tissue just inside the lips. Thin strips of mucosa are removed (not the outer skin) on both labia and the exposed mucosa, which is then joined by stitching the two opposing faces together leaving a gap at the bottom for urine to pass freely. This may be done with continuous stitch in the mare that is free of scar tissue and new to the caslick procedure, or interrupted stitch if the site is more damaged or sloped. This simple procedure is quick to perform with the surgical site, generally, fully healed within 10 days. In photo right the vulva has been prepared with cleansing, local anaesthetic inserted on the surgical site making it look “pumped up” and the mucosa removed. The stitching begins.

Routine perineal inspections and maintenance of the caslick
Winter month inspection:
routine inspections of the vulva are easy during stud season, but often – during the winter months – this can be overlooked. In the dry mare, when there may be natural or intentional weight loss, the vulva may become a little more sunken and beyond critical point, exposing her to the risk of pulling in air and initiating the onset of uterine infection. This also applies to the pregnant mare.
In the pregnant mare, her body shape can change quite a bit during this period due to the added weight of the growing foetus dragging down the uterus and could cause the vulva to sink … and therefore become sloped. This is seen more in the already aging mare and can develop quite rapidly.
Breeding season scanning sessions: By regularly scanning the uterus in conjunction with the follicles, signs of the presence of air or infection can often be picked up indicating the need to consider giving the mare a caslick or extending it further.
Open Caslick prior to foaling and stitch back down post foaling: It should go without saying, but one of the main reasons that the perineal region can become grossly damaged is a result of a foal being forced through a caslick. The mare should be re-stitched soon after foaling.
If a mare with a caslick aborted in the later stages of gestation, the inspection and repair of the caslick must be addressed immediately as part of the post abortion treatment program. The mare that aborted in early pregnancy should be scrutinised as a possible candidate for a caslick during early reproductive examinations.
Check the mare’s caslick pre service: Always check the vulva and remove any suture material from the caslick site. The boys in the breeding barns hate it when this is not done for them. The stallions hate it even more if this procedure is neglected….ouch!
Check the mare’s caslick post service: The stallion master may open the caslick for the event of serving as some stallions are well endowed or the caslick may be very tight so the opening is not sufficient for the stallion to enter easily without damaging the vulva site. As a farm that previously had a number of stallions, I would not open the caslick on their behalf unless she is really stitched down tight. It is amazing how much the vulva can stretch during the act of serving. Stallion personnel will know if the caslick will require a little snip, and by how much according to the stallion.
Vaginal entry for internal veterinary treatments: Performing uterine treatment programs, or manually inspecting the reproductive tract, can result in the vet tearing the caslick a little. At the end of any treatment program the caslick should be either reviewed as a possible requirement or checked if a quick repair job is needed.

1) Whenever inspecting a caslick site, it is well worth ensuring there are no fistulas (holes) in the caslick. This can in fact accentuate the wind sucking effect, as the fistula acts as a pressure pump dragging in air. Most fistulas are found in the top part of the caslick, where stitching is a little more awkward to perform. To do this requires cleaning the perineal region and running a clean finger inside the lips down the caslick site. Do not do this on a fresh caslick as it will break down.
( Photo Right: a fistula or hole in the caslick where the surgery failed to adhere along the full length of the site)
2) When purchasing a mare, inspect her vulva for premature aging. Check degree of slope and amount of scar tissue. To have a caslick is quite ok, as long as the degree of slope is age relevant. A very sloped young mare will indicate a shorter reproductive life.
3) The over extension of a caslick may inhibit the ability for the urine to be expelled properly, causing splash back and therefore pooling in the vagina. Naturally this will cause irritation and other fertility concerns.

It all boils down to the axiom: look after the fanny and the fanny will look after you!

Related Stories:

At Home Care of the Pregnant Mare

No One Home: Causes of Infertiltiy and Sub-Fertilty in Mares


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