| Introduction to breeding |
 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. 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 with hormone treatments. 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 On occasions 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. This should be done at the start of second stage labour or it may be done by the vet a few days 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. There are two types 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. 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 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 is done during dioestrus. 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 Contagious Equine Metritis (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. Blood test for Equine Viral Arteritis (EVA) A blood test should also be taken to test the mare for EVA prior to breeding and the stallion should also be confirmed clear before a mare visits him. Both the CEM swabs and EVA bloods take some times for the results to be confirmed, so it adviseable to have them done at least 10 days before the mare is due to go to stud. |
