Selecting a Broodmare

There are three important questions that anyone considering breeding from a particular mare should ask.

• Is she suitable for breeding? Traits such as conformation and temperament are highly heritable and should be important considerations when selecting the mare and stallion. Mares should be selected for quality of type or performance and not simply because they are no longer suitable for any other purpose. Those with serious conformational defects should not be bred from as soundness is very important
• Are suitable facilities available? Consideration must also be given to the facilities required. You will need a foaling box and suitably fenced, good quality pasture. Ideally the field should be shared with another mare and foal.
• Can I afford it? Stud fees, livery charges and routine and unexpected veterinary bills can add up to a substantial sum and there is no guarantee that a healthy foal will be produced or if that foal will mature into a quality horse.

Mare Reproductive Cycle - General Information

Most mares have a 21 day oestrous cycle. This is divided into:
• Oestrus (average 5 days)
• Dioestrus (14 – 16 days)

The cycles begin at puberty (approximately 18 months) and continue throughout the mare’s life.

Oestrus
The mare is receptive to the stallion and is said to be ‘in season’. Typical signs of oestrus include:

• Adopting a urinating stance with the tail raised and passing small squirts of urine
• Opening and closing the vulval lips. This is known as ‘winking’

During this time one or more follicles on the ovaries increase in size and rupture to release an egg (ovulation). The mare normally ovulates approximately 24 hours before the end of oestrus. The exact timing of ovulation can only be determined by performing repeated ultrasound scans of the ovaries. The maturation of the follicle can be monitored by the vet by successive rectal and ultrasound examinations.

Dioestrus
The mare is no longer receptive and may behave aggressively towards the stallion. She is likely to put her ears back, swish her tail and may squeal or lash out.

Control of the oestrous cycle
The mare has a seasonal breeding period which is influenced by factors such as daylight length, temperature and nutrition. In cold winter months, most mares stop having oestrous cycles and their ovaries become small and inactive. In February and March when they begin cycling, some mares have very long periods of oestrous behaviour but fail to ovulate. There is considerable individual variation between mares.

The oestrous cycle is under hormonal control. When problems arise, oestrus or ovulation can sometimes be induced medically with hormone treatments. Vets sometimes describe this as "short cycling".

Encouraging early cycling in the mare
The mare is a polyoestrous breeder. Environmental and other effects can exert a  huge effect on the mares reproductive cycle, especially during the ‘transitional period’. The transitional period is the period between Winter anoestrous (when the mare does not cycle) and the onset of cyclic activity in the spring. Transition period also occurs in Autumn when mares cease cycling and go back into Winter anoestrous.There are exceptions to this rule, as some mares (up to 15%) will cycle all year round.

The production of hormones that ‘switch on’ mares to start cycling is controlled by daylight. Therefore, the natural breeding season in the mare is strongest from May until August, when the days are longest and the weather is warmest.
During the spring months i.e. Feb-April the weather can be very variable and daylight hours are still relatively short. This in turn creates very variable oestrous activity in the mare, with one or more of the following scenarios often occurring:
1.    No oestrous behaviour seen.
2.    Erratic and often confusing signs of oestrus behaviour.
3.    Oestrous behaviour seen, but no dominant follicle growing and hence no ovulation.
4.    Long or unpredictable length of cycle

During this period it is often difficult to predict to predict when the mare will ovulate and thus determining the precise time to cover a mare. Because it is not cost effective to use stallions or stored semen during this unpredictable period, it is often wise to artificially manipulate the mare to encourage normal cycling and shorten the transitional period as much as possible. This can be done in a number of ways:
1.    Artificially increasing daylight. Studied have shown that increasing daylight to 14-16 hours (natural plus artificial) daily for a minimum of 8-10 weeks can induce normal cycling.
2.    Progestogens- progesterone treatment suppresses the release of LH during administration. This allows LH to build up which is stored. When progesterone treatment is stopped, a huge surge in LH induces a strong oestrous which usually results in ovulation. Regu-Mate (Altrenogest) given orally once daily for 10-15 days is commonly used during the transitional period. Mares come into season 4-7 days and ovulation occurs 7-12 days after treatment has stopped.

Gestation Length
The gestation (pregnancy) length is 11 months (340 days), but considerable variation occurs with a range of 320 – 360 days, and sometimes even longer.

Stallion selection
The choice of stallion should be made after consideration of the following factors:

• Conformation
• Soundness and freedom from hereditary conditions
• Performance records – achievements during his working career
• Temperament – ideally calm and kind
• Size
• Fertility record
• Cost and terms of the stud fee
• Distance
• Availability of artificial insemination and success thereof.

It is worth travelling to view the selected stallion. If at all possible, ask to see some of his offspring. Before arranging to send the mare to be covered, find out from the stud whether they require clitoral and/or endometrial swabs to be taken before or after the mare arrives.

Veterinary care of the brood mare
The vet is usually consulted at several stages of the breeding programme eg:

• Gynaecological examination prior to covering
• Pregnancy diagnosis
• Pre-foaling vaccination
• Post-foaling checks

Pre-breeding checks
The purpose of the examination is to check for any problems that could affect the mare’s ability to conceive or carry the foal to full term. Ideally the checks should be made early in the season so any problems can be detected and treated.

History
The vet will want to know her:

• Name
• Age
• Breed
• Previous breeding history
• Health problems including lameness
• Vaccination status
• Body condition

Gynaecological examination
This includes:

• Inspection of the vulva, vagina and cervix
• Rectal palpation and ultrasonographic examination of the uterus and ovaries. Ultrasonographic examination can reveal the presence of abnormal amounts of fluid within the uterus and endometrial cysts, which can be mistaken for an embryo if not identified pre-breeding.
• Taking swabs from the clitoral fossa and sinuses
• Taking a swab from the uterus for bacterial culture and examination of the cells under the microscope.

Preparation
If purpose-built stocks are not available the mare should be examined in a stable. She must be adequately restrained by a competent handler and it is helpful if her tail is bandaged. The vet will require:

• A bucket of clean, warm water
• An assistant to hold the tail out of the way
• A power supply for the scanner

Sometimes it is necessary to apply a twitch or sedate the mare for the examination.

Assessment of the vulva
The vulva is checked for any signs of a discharge. The vulval lips should be vertical and meet together in the midline, forming a firm seal. If the vulva slopes forwards, the seal is easily broken and air may be sucked into the vagina as the mare moves. Aspiration of air and contamination by faeces can lead to inflammation of the vagina, cervix and the lining of the uterus, with resultant infertility.

If the vulval conformation is poor, a Caslick’s operation may be carried out. This involves suturing the upper part of the vulval lips together under local anaesthetic. This must be opened before the mare foals or she will tear during foaling. Ideally this should be done at the start of second stage labour BUT IT MEANS YOU MUST BE THERE TO ASSIST THE MARE, or it may be done by the vet 1 - 2 weeks prior to foaling.

Swabs and smears
Swabs are taken to check for inflammation or infection of the reproductive tract. An infected (dirty) mare will not conceive, so covering her is a waste of time and money. More importantly, a mare with venereal disease will infect the stallion and any mares he subsequently covers. Maiden mares are included in this regime. YOU MUST CHECK EXACTLY WHAT THE STUD REQUIRES AS IT CAN VARY ENORMOUSLY. There are more than one type of swab:

Clitoral swab
A clitoral swab is taken before or at the start of the breeding season. It can be taken at any stage of the oestrous cycle. A narrow-tipped swab is introduced into the clitoral sinuses and clitoral fossa. It is then cultured for bacteria that produce venereal disease. These include Tayorella equigenitalis, the organism responsible for Contagious Equine Metritis (CEM), Klebsiella pneumoniae and Pseudomonas aeruginosa. The CEM culture takes 7 days,so book your appointment with Bell Equine 10 days before you need the results.

Endometrial swab and smear
The endometrium is the inner lining of the uterus. An endometrial swab and smear can only be taken when the mare is in season and the cervix is relaxed. This is usually done early in oestrus so the mare can be covered in the same oestrus if the results are satisfactory. Using a disposable cardboard speculum, a sterile swab is passed through the cervix into the uterus. Following withdrawal it is cultured for 48 hours to see if any bacteria grow. A second swab is then inserted into the uterus and gently rubbed against the endometrium before being withdrawn and rolled onto a microscope slide. The slide is examined for the presence of endometrial cells and neutrophils (pus cells). The presence of increased numbers of neutrophils and a positive culture of bacteria is indicative of inflammation of the endometrium, known as endometritis.

Treatment of endometritis
When the laboratory results show the mare is suffering from endometritis, she is likely to be treated with infusions of sterile saline and antibiotics into the uterus for a period of 3-5 days. A mare with endometritis will have reduced conception rates or may suffer from Early Embryonic Loss, so it is important to identify and treat these mares before covering.

A second swab and smear must be taken early in the following oestrus. If the treatment has been successful and there is no evidence of endometritis, the mare can be covered.

Endometrial biopsy
If the mare fails to conceive, or the swabs and smears reveal persistent or recurrent infection or inflammation, an endometrial biopsy may be taken. This can be done at any stage of the cycle but is easiest during oestrus.

Biopsy forceps are passed through the cervix and a small piece of endometrium is removed and sent to a laboratory for histology (examination of the tissue under the microscope). This reveals the extent of any inflammatory or degenerative changes in the endometrium. Treatment can then be recommended and a prognosis for successful breeding given. A second biopsy is taken approximately one month later to assess the results of treatment.

Endometrial endoscopy
Examination of the endometrium with an endoscope can provide the vet with valuable information, such as the presence of cysts and damage sustained during previous pregnancies. The normal endometrium is smooth and pink in appearance. An inflamed endometrium may appear very haemorrhagic and have adhesions which obstruct the passage of the endoscope.

The control and treatment of venereal disease
1 Contagious Equine Metritis (CEM)

CEM caused by Tayorella equigenitalis is a notifiable disease in the UK. Any occurrence must be reported to the Divisional Veterinary Manager of DEFRA.

Clinical signs
Most stallions carrying the disease show no outward signs. Mares may have a grey, mucoid vulval discharge or they can also be symptomless carriers of the disease.

Transmission
The disease is transmitted:

• During mating including artificial insemination
• During teasing
• On hands or equipment if hygiene standards are poor.

Diagnosis
Diagnosis is confirmed if the organism is grown on swabs from:

• The clitoral fossa and sinuses, the endometrium or vaginal discharge of mares
• The urethra, urethral fossa, penile sheath and pre-ejaculatory fluid from stallions

The swabs must be sent to an approved laboratory.

Treatment
Stallions are treated by thorough cleaning of the penis with an approved antiseptic solution and application of an antibiotic ointment for 5-7 days following removal of all accumulated smegma.

Mares with endometritis are treated with intrauterine infusions of antibiotic and thorough cleaning of the clitoral region and topical antibiotic treatment. With stubborn infections that are difficult to clear, surgical removal of the clitoris may be performed.

Freedom from infection in mares is confirmed by three negative clitoral swabs taken at intervals of at least seven days and three negative endometrial swabs taken during successive oestrous periods.

Stallions require three sets of negative swabs taken at intervals of at least seven days before they can be confirmed free of infection. In addition, the first three mares mated or inseminated by the stallion should have clitoral swabs taken three times at intervals of at least seven days, starting two days after mating or insemination. These must be negative.

Control
If a case is confirmed, there is a Code of Practice published by the Horserace Betting Levy Board (HBLB) that must be strictly adhered to www.hblb.org.uk . This includes:

• Stopping all breeding activity immediately
• Isolation and swabbing of infected horses
• Swabbing of at risk contacts
• Notification of the relevant breeder’s association
• Notification of owners of mares who have left the premises, are booked to the stallion or have been inseminated with semen
• Testing of stored semen
• Foaling of pregnant mares that have been exposed to the infection in isolation. The placenta must be burned and both filly and colt foals swabbed.

Breeding should not be resumed until the premises are confirmed as free from the disease.

Prevention
The disease can be prevented by strict adherence to the recommendations for swabbing in the HBLB Code of Practice. The swabs should be taken from mares and stallions after 1st January of the year in which breeding activity is planned. Additional swabs are taken from stallions in the middle of the breeding season.

2 Equine Viral Arteritis (EVA)
EVA is also a notifiable disease in the UK. The highly contagious virus is common worldwide including mainland Europe.

Transmission

• Aerosol spread - direct contact with droplets from the respiratory tract e.g. coughing or snorting
• Infected semen - during natural covering and Artificial Insemination

• Contact with aborted fetus and placenta of infected mares.
  

Clinical signs

• Fever, depression, lethargy
• Stiff movement
• Runny nose
• Conjunctivits ('pink eye')
• Swelling around the eye, lower legs and reproductive tract
• Abortions.

Diagnosis

• Serology - blood samples to look for antibodies to the virus.
• Virus detection tests - nasopharangeal swab, urine, semen and aborted material. In the case of abortion, the fetus and placenta are sent to the lab.

Treatment
There is no effective treatment for EVA.

Prevention

Establish freedom of infection before breeding - routine blood test taken at prebreeding exam.

3 Equine Infection Anaemia (EIA)

EIA is sometimes referred to as 'swamp fever' and is notifiable. It is common worldwide, including Europe. There were two confirmed cases in January 2010 in Wiltshire UK after importation from Romania and Belgium.

Transmission

• Insect vectors such as biting flies (horse flies and stable flies)
• Bodily fluids - saliva, nasal secretions, faeces, semen, blood and milk
• Contamination of equipment with blood or other bodily secretions
• From mare to foal via the placenta, or colostrum or milk in newborn foals

• Recurring fever
• Anaemia
• Oedema
• Emaciation
• Death

Treatment
Infected horses are euthanased on welfare gounds and also to protect the rest of the horse population from infection under government notifiable disease regulations.

Prevention

No vaccine is available therefore control is based on establishment of freedom of infection. Serology is performed on blood samples taken at pre-breeding exams.

4 Equine Herpesvirus (EHV)

EHV is a common virus that affects horse populations worldwide. Two forms of the disease exist; EHV-1, which causes repiratory disease, abortions and paralysis; and EHV-4, which usually causes respiratory disease only but can cause abortions.

Transmission

• Aerosol droplets from the respiratory tract e.g. coughing and snorting
• Contact with aborted fetus, fetal fluids and membranes
• Foals born from infected mares are highly contatious and shed the virus in the enviroment
• Indirect transmission from the enviroment as the virus can survive for several weeks
• Horses commonly act as carriers and shed the infection without showing any clinical signs

Clinical signs

• Develope 2 weeks to months after infection
• Mild fever, coughing and nasal discharge
• Foals that are infected in the womb from the mare are usually born with weakness, jaundice, difficulty breathing and neurological signs. They usually die within 3 weeks
• Abortions
• Paralysis - inco-ordination of the hind limbs, urinary incontinence and in severe cases lying down and unable to stand (recumbancy)

Diagnosis

• Virus isolation is performed on nasopharangeal swabs and blood samples
• Aborted fetus - detailed samples are collected by the vet from the aborted fetus and placenta

Treatment

No specific treatment for EVH. Rest, intensive care and nursing are necessary to minimize secondary bacterial infections.

Prevention

Management practices that reduce viral spread;

• New horses should be isolated for 3-4 weeks before mixing with resident horses
• Pregnant mares should be kept together in small fixed groups according to their stage of gestation. No mixing of pregnant mares with weanlings, yearlings or any horses in training that are high risk carriers.
• Stressing mares in late prenancy should be avoided, to minimize the activaion of latent carriers
• Isolate affected horses and seek veterinary advice.