( BREEDING )
The Technicalities of Equine Artificial Insemination by Gemma Kirk BVetMed MRCVS
L
ooking to breed your mare this year and considering Artificial Insemination (AI)? Do you have lots of questions or perhaps just
interested in learning more? This article discusses the technicalities of semen processing and AI and hopefully answers your questions.
WHY CHOOSE AI? AI has many benefits to natural cover including reducing the risk to personnel (mare and stallion handlers), splitting of ejaculates so one ejaculate can be used to inseminate multiple mares, thus reducing the work load for busy stallions and, increasing the availability of stallions via national and international shipment of semen and reduced risk of spread of venereal diseases. The use of frozen semen also allows stallions to continue to be bred from when out competing or even aſter they have passed away. To reduce the spread of venereal diseases as of the 1st January each year each stallion is required to be tested for Contagious Equine Metritis (CEM), Pseudomonas aeruginosa and Klebsiella pneumonia, Equine Viral Arteritis (EVA) and Equine Infectious Anaemia (EIA). Semen that does not have relevant health papers to confirm it is free from diseases should not be inseminated into the mare. (HBLB codes of practice
https://codes.hblb.org.uk).
HOW IS SEMEN COLLECTED?
urospermia (urine in ejaculate) or haematospermia (blood in ejaculate) or a failed ejaculation.
Microscopic semen evaluation Missouri Artificial Vagina (AV)
In most cases semen is collected using a dummy mare and an artificial vagina (AV). The stallion is teased, mounts the dummy, ejaculates into the AV and collected into a bottle attached at the end of the AV. One of the most commonly used AV’s is a Missouri AV. (See photo). A filter, fitted at the neck of the bottle removes the gel fraction from the ejaculate as quickly as possible reducing the detrimental effects of gel on the sperm.
WHAT IS INVOLVED IS SEMEN ANALYSIS AND PROCESSING? Once collected semen is very sensitive to light and rapid changes in temperature. It is collected into a bottle and protected from light with an insulated cover, analysed and processed as quickly as possible to minimise deterioration in the ejaculate. Water is spermatotoxic so it important to have a designated clean and dry area for processing semen. Semen is analysed grossly and for motility and concentration before undergoing different levels of processing or extending dependant on the stallion and it’s intended use (fresh, frozen or chilled). Initially the colour of the ejaculate is assessed. Discolouration could indicate problems such as
26 MAY/JUNE 2019
The volume is then measured and documented. Motility is assessed for both raw and extended semen under the microscope on a preheated slide and cover slip to avoid cold shock to the sperm (see photo). Both the total and progressive motility (sperm that move progressively in a straight line) is assessed. A certain number of progressively motile sperm cells are necessary per insemination dose to maximise pregnancy rates as discussed below. Semen concentration is commonly measured using a haemocytometer. The concentration of the semen dictates the volume of extender required and the number of doses the ejaculate can be divided into. One insemination dose requires a minimum of 500million morphologically normal progressively motile sperm. It is good practice to also assess sperm morphology, this is of particular use for investigating sub-fertile stallions. In more recent years computer soſtware has been developed to further evaluate semen. Semen extender provides the sperm with all the appropriate nutrition required for it remain viable until being inseminated into the mare. Different stallions’ semen will look better with different extenders and cope with the chilling process differently. Some stallions’ semen however may remain viable and with good motility for three or more days. Performing tests with different extenders then chilling and evaluating the motility at different time points post collection can help when deciding which extender best suits the stallion. Centrifugation is used in the processing of frozen semen but can also be of use to improve the quality of the ejaculate when processing chilled semen via removal of the seminal plasma.
WHAT IS THE DIFFERENCE BETWEEN FRESH, CHILLED AND FROZEN SEMEN? Semen is collected and analysed using the same methods for fresh, chilled and frozen semen. Differences arise however in how the ejaculate is processed and in what circumstances each type of semen is used. • Fresh- Semen is processed and extended so it is more concentrated than chilled semen. It is used when the mare and stallion are in close proximity or on the same premises and is inseminated within a few hours from collection. It can be useful to help boost pregnancy rates for stallions’ semen that does not chill well or in more difficult mares.
•Chilled- Semen is processed and extended dependant on the concentration of the ejaculate. One ejaculate can normally be split into multiple insemination doses. It is then distributed in a chill
pack and inseminated within 24-48 hours of collection. This way semen can be posted within the UK and Europe. If couriered from stallion to mare it can be used for same day inseminations. • Frozen semen- Semen is processed and added to equal volumes of extender and centrifuged using a cushioning agent, to protect the sperm. A set volume (dependant on concentration) of designated freezing extender is added to make the ejaculate a set concentration. The concentration of sperm per millilitre or 0.5 millilitre straw dictates the number of straws per insemination dose. Semen is then drawn up into straws, sealed, chilled then frozen and stored in liquid nitrogen containers (see photo). As per chilled semen one ejaculate can normally be split into multiple insemination doses. A minority (~30%) of stallions’ semen does not tolerate the freezing/ thawing process so freezing is not an option in such cases. Test freezes can be performed to assess how well the stallions’ semen copes with the freezing/ thawing process.
Frozen semen tanks HOW IS THE MARE INSEMINATED?
Frozen semen straws, insemination catheter and metal stylet for insemination of frozen semen into the mare
Aſter careful monitoring of the mare and drugs to control the time of ovulation semen is inseminated into the mare at the perfect time. Chilled and fresh semen is generally received in a chill pack in non- spermicidal syringes and deposited through the cervix and into the uterus using an insemination catheter. This is done prior to ovulation. Frozen semen straws are removed from liquid nitrogen tank and defrosted by immersion in a water bath at a set temperature for a set period of time. The semen is then drawn up from the straws into a syringe or inseminated using a metal stylet via an insemination catheter. Frozen semen can be deposited through the cervix and into the body of the uterus or into the end of the horn of the uterus adjacent to the ovary from where the follicle will be released (deep intrauterine insemination). Most commonly frozen semen is inseminated at the time of or 4-6 hours post ovulation.
For the latest news visit
www.centralhorsenews.co.uk
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96
