Artificial Insemination

Transcription

1 Artificial Insemination Artificial Insemination (A.I) is a technique used to transfer semen from a stallion into the uterus of a mare during the correct stage of her oestrus cycle. A.I has become very popular in stud medicine for the advantages that it offers compare to natural covering (though not allowed in racing thoroughbreds), but, as much as it s exciting breeding from your own mare, it s important to understand how it works and the pros and cons before deciding to take this route. What are the advantages of A.I You can choose a stallion that is competing without interrupting his schedule Allows you to choose the best stallion for your mare from all around the world and too far away to make natural covering viable You can choose a stallion of which semen was frozen before his death or castration Improve bloodlines for a rare breed also encouraging its geographical spread Reduce risk of breeding injuries to both the mare and the stallion More disease control by preventing skin contact such as in natural service and also by checking the stallion with swabs for Contagious Equine Metritis (CEM) and blood test for Equine Viral Arteritis (EVA) and Equine Infectious Anaemia (EIA) every year before the semen collection Permits use of valuable stallions and mare with breeding problems Allows mares to be bred at the best time for conception Permits evaluation of semen at each collection and immediate recognition of minor changes in seminal quality. What are the disadvantages of A.I Cost AI with chilled or frozen semen generally has a lower conception rate (chance of producing an embryo) than natural covering Risk to the mare when performing rectal examinations Like for natural covering, AI does not always result in a live foal the following year. Semen presentation

2 Management of the mare and timing of insemination will be determined by which semen is chosen (fresh, chilled or frozen) but it is also very important to check in which of the three ways the semen is preserved best and travels best for the specific stallion. Fresh semen Fresh semen is usually used on studs and only lasts outside the horse for short periods of time. It always has the highest fertility but mares and stallions need to be at the same location for insemination. Also fresh semen is usually the least expensive method, because requires no processing and less frequent veterinary checks. Chilled semen The semen gets refrigerated immediately after collection and transported in chiller packs either by post or manual collection, staying viable for 2-3 days. The conception rates are greater than for frozen semen. With chilled semen it s important to find out which days of the week the stud collects from the stallion and how much notice you will have to give for them to collect and send the semen. Frozen semen After collection the semen is separated and added to a preservative. It is then frozen and stored below freezing, usually in dry ice. The semen can then be transported great distances in liquid nitrogen container and last for many years as long as it is kept frozen. Once arriving at its destination it can be defrosted, re-awakening the sperm and inseminated into the mare. Compared to chilled semen, the freezing and handling process slightly reduces the viability of the sperm and conception rates, therefore requires mares to be inseminated immediately before or after ovulation. However advantages are that breeders can use stallions which are still competing and the semen can be sent well in advance of the mare being in oestrus, avoiding the last minute delivery of chilled semen, which may not arrive on time. Pre-breeding check Prior to embarking on an A.I. program it is important the mare is examined to ensure that she is fit to breed and asses for factors that may reduce fertility. The pre-breeding check, best if performed safely in stocks, consist of a physical examination to evaluate vulval conformation, a rectal examination to check the cervix for any abnormalities and ultrasound scan to look for uterine cysts and to see at what stage of the cycle the mare

3 is. At this time we will also be able to take clitoral swabs and, if required by the stud, to do blood tests to check your mare is free of venereal disease. Timing the insemination Mares cycle between February and October (cycles at the beginning and the end of the season can be very irregular) and have a day cycle, with oestrus (the receptive period) lasting 3-6 days. To have a successful insemination resulting in pregnancy it s important to place the semen in the uterus when the mare cycles regularly and at the correct stage of the cycle, so when she is in season and close to ovulation. Signs of oestrus in the mare include tail raising, opening and closing of the vulva (winking), frequent posturing and urination and some may, also, become anxious, aggressive, sensitive around their flanks and reluctant to work, though can be difficult to detect and irregularly shown. Ultrasound scans of the ovaries and uterus allows detection of the stage of the cycle and, measuring the size of follicle, we can predict when the mare is coming close to ovulation and inject her with drugs that induce it. The best time to inseminate varies with the type of semen used: for fresh and chilled, AI need to be done within hours of ovulation whereas for frozen AI it needs to be done within 6 hours of ovulation, which means a greater number of scans are required both during day and night. Pregnancy Diagnosis The most appropriate time to determine the pregnancy is between days 14 and 16 following ovulation through a transrectal ultrasound. At this time it s very important to check for multiple pregnancies and, if necessary, deal with it before the embryo becomes attached to the lining of the uterus and makes it difficult to squash the twin days

4 embryonic vesicle A further scan around 28 days to check the normal development by identification of the foal s heartbeat is advised. This also reduces the risk of missing detection of a twin pregnancy. If the mare is not pregnant then she should go back in season again allowing the program to be repeated, hopefully, with a more favourable outcome. 2-3 month pregnancy scan Thinking Of Putting Your Mare In Foal? Whilst the thought of having a lovely home bred foal which in time matures into your perfect riding horse is a lovely idea this may not be the reality. The decision to put your

5 mare in foal needs much planning, time and effort. There are four main questions that anyone considering breeding from a particular mare should ask: Is she suitable for breeding? Conformation, temperament and performance are key. A mare shouldn t be bred from simply because she is no longer suitable for any other purpose! Are suitable facilities/expertise available? Including facilities not just for the infoal mare but also for foaling, for the new born foal and in time for a growing youngster. Do you have the experience to deal with a foaling mare and potential problems or would she be better at stud? 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/the foal will mature into a quality horse. Breeding can be a risky business for both mare and foal. What are my plans for the foal? Are you breeding to sell or breeding for yourself? What will your circumstances be in 4 years time when the foal is grown up and ready for riding? Having considered your options and decided to go ahead your next decision is which stallion to use. This is influenced by your mare in terms of conformation and abilities but also what the foal s intended use is. Considerations include conformation, soundness, performance, temperament, fertility, cost and terms of the stud fee and availability of chilled/frozen semen. So you have a suitable mare and have found the ideal stallion to complement her, what next? Your vet will need to come out and perform some pre-breeding checks prior to commencing the process of actually getting her in foal to ensure the best chance of success. These include; Swabs and blood tests to check for specific bacterial and viral diseases, namely Contagious Equine Metritis (CEM) and Equine Viral Arteritis (EVA) It is worth getting these done early in the season to save time later on. Gynaecological examination to inspect the mare s vulva, vagina and cervix. Ultrasound examination per rectum to ensure both the uterus and ovaries are normal and to check the mares stage of the oestrus cycle. Uterine swabs can be

6 taken at this stage if there is any concern over infection/previous fertility issues to allow appropriate treatment. If your mare is not in season at the first scan then she will be given drugs to bring her in to season. Once she is in season your vet will need to visit regularly to perform repeated ultrasound scans to ensure that she is inseminated at exactly the right time to optimise chances of pregnancy. If you are using frozen semen the number of visits and scans is much increased due to poorer semen quality. It is essential that you have adequate facilities to restrain your mare for these examinations, some mares need sedation for everyone s safety. Remember to liaise with the stud and ensure that the semen is available and delivered when requested accompanied by the correct paperwork contact the stud with plenty of notice! After insemination we will visit again to ensure that all has gone to plan, that the mare has ovulated and there is no adverse reaction to the semen. Some mares will need further treatment at this stage including further injections and flushing of the uterus. Assuming all goes to plan then pregnancy diagnosis will be performed between days and at 30 days where hopefully we will identify a heartbeat! Unfortunately many mares (especially older ones) won t get in foal first time so be prepared to go through it all again! In a nutshell consider your options carefully, contact us in plenty of time to discuss your plans, be aware that your mare will need several visits prior to insemination and then keep your fingers crossed for a happy bouncing foal!