THE ROLE OF THE STUD VETERINARIAN

Hundreds of years of history and a little (un) common sense testifies to the fact that mares go in foal when covered by a stallion! It is not surprising then that the most common question asked of stud veterinarian and stud owners and managers by mare owners is:-

"Why does my mare need to be examined by the vet? She goes straight in foal every year without any problems, without all this messing around".

It is a fair comment and one to which there is no simple or easy response. All too often we hide behind scientific jargon in our response: choosing to ignore that they are probably right!

I would define the stud veterinarian's duty as: -
"To achieve the maximum mare fertility while protecting the stallion from over-use or injury".
Any assistance to stud management that occurs as a result of achieving this aim is only incidental (to the mare owner).

To understand how the stud veterinarian goes about achieving their aim, one needs to know a little about the mares reproductive cycle: -

Most mares cycle, or come into season (oestrus), every twenty-one (21) days. They remain in season, or oestrus, from three (3) to seven (7) or more days. The length of their oestrus decreases as the season progresses. Cycling begins in wet mares (mares with foals at foot) at the foal heat (nine days after foaling), and in dry or barren mares with the onset of spring, as a response to increasing day length. Most mares ovulate (release their eggs from a follicle), on the last few days of oestrus. If semen is present, conception (fertilisation) occurs in the oviduct (fallopian tube) and the conceptus (ovum) remains there for six (6) days before entering the uterus. When ovulation (rupture of the follicle) occurs on the ovary, a corpus luteum is formed which secretes progesterone: a hormone which maintains pregnancy. Sound simple? Well it can be; but there are a hundred places it can go wrong and not all mares have read the book!

Let's look at some of the problems, which can occur, and how the stud veterinarian can prevent or treat them when they do occur.

INFECTION OF THE MARE OR STALLION:
Horses, like people, can become infected with sexually transmitted diseases (STD'S). The stud veterinarian can check the mare or stallion by swabbing to prevent this from happening. Some older, particularly maiden mares are also prone to becoming infected by the 'normal' bacteria on the stallion's penis.

PROLONGED OESTRUS OR FAILURE TO OVULATE:
This is a common problem particularly early in the breeding season. Some mares will remain in season for weeks and unless checked will require regular service by the stallion leading to overuse or other mares missing out. Fortunately, follicles are palpable structures on the ovary, which can be felt by the stud veterinarian by feeling through the mare's rectum; hence the old term 'follicle testing'. The advent of ultrasound and other advances have allowed the stud veterinarian to learn a lot more about the mare's status by rectal palpation than simply follicle testing, Most stud veterinarians now refer to the procedure as 'palpation of the genital tract'. Palpation allows the stud veterinarian to accurately determine when the mare is about to ovulate so that she needs less cover by the stallion. Similarly, the vet is able to recheck after cover to confirm that ovulation has occurred. A drug called 'Leutenising Hormone' can be given to ensure ovulation will occur if a suitable follicle is present.

FAILURE TO FORM A CORPUS LUTEUM:
Ultrasound allows the stud veterinarian to check that a functional corpus luteum has formed so that if the mare goes in foal, the pregnancy will be maintained. When in doubt, the vet can administer supplementary hormone therapy (progesterone).

FAILURE TO THE CORPUS LUTEUM TO REGRESS IN THE NON-PREGNANT MARE:
If your mare does not conceive, the corpus luteum must regress before the mare will return to season for repeat servicing. Failure to regress can be determined by ultrasound and, when it occurs, supplementary hormone therapy can be given to overcome the problem (prostaglandin).

ACCUMULATION OF FLUID OR INFECTION IN THE UTERUS AFTER SERVICE:
Again this can be detected by ultrasound after service and if it occurs the mare will normally not go into foal. When it is found it can be treated with hormones (oxytocin) and/or antibiotics or plasma.

TWINS:
Most of you will be familiar with the problems associated with twins. Most mares will not carry them to full term leading to loss of a years production but, worse still, many of those mares will not go into foal the subsequent year; leading to two years loss of production. Early ultrasound examination from twelve (12) days after conception allows early recognition of twins so that one can be removed allowing the second to develop normally. This must be done very early in the pregnancy to be most successful.

The above represents only a fraction of what the stud veterinarian can do for your mare, but it will give you some idea of their duties. Sure, your mare might go in foal without the vets, but with their assistance, her chances of conceiving as early in the breeding season as possible and carrying that foal to full term are greatly enhanced. More often than not the vets fees are more than absorbed by the reduction of time the mare must be at the stud (agistment) and a reduction in the number of years the mare may be barren. Some mare owners maintain their right to refuse veterinary services and that is their decision, but it is also the right of the stud master to insist on veterinary care if only to protect his valuable stallion from infection, over-use or injury, and to maximise their chances of achieving a positive pregnancy test so that they can receive their service fee and reduce the need for free returns.

EXPLANATIONS FOR ITEMS WHICH MAY APPEAR ON YOUR ACCOUNT.

Clinical Examination & Palpation & Scan:
This refers to the rectal examination and ultrasonic examination performed on your mare to determine the stage of the reproductive cycle and time of service, ovulation etc. B) Pregnant or non-pregnant C) Presence or absence of fluid in the reproductive tract (endometritis).

Inject Oxytocin:
Oxytocin is the drug used to cause contraction of the uterus and removal of fluid from the reproductive tract. Oxytocin may also occasionally be used for milk let down, retained placenta and induction of partuition.

Inject Prostaglandin:
Prostaglandin (PG) is the drug used to remove the corpus luteum (if present) from the ovaries and bring your mare into season (for covering). It will not work in the absence of a corpus luteum i.e. anoestrus or spring oestrus. Prostaglandin may also occasionally be used to remove fluid from the uterus or to induce partuition.

Insert CIDR / PRID:
CIDR's or PRID's are progesterone releasing devices that are placed in the uterus to encourage the development of follicles. It is a cheaper variant to using Regumate. They may also occasionally be used to maintain pregnancy.

Inject Leutenising Hormone or Ovuplant:
Leutenising hormone (LH) or Ovuplant are drugs used to induce ovulation. They are used to minimise the number of services your mare may require.

Antibiotic Infusion:
Antibiotic infusions are a mixture of antibiotics inserted through the cervix and into the uterus after service. They remove bacteria pushed into the uterus at service or insemination. Occasionally your mare may be treated in a similar manner using her won plasma. This stimulates an immune response in the uterus to any infection.

Treat Twin Pregnancy Occasionally your mare may be diagnosed with a twin pregnancy. Normally mares will not carry a twin pregnancy to full term. Provided the twins are diagnosed early enough by ultrasound, one of the pregnancies may be crushed through the rectum. Normally the remaining pregnancy will develop normally.