Hampton Veterinary Centre Hampton Veterinary Centre Hampton Veterinary Centre

A - Z of Equine Artificial Insemination

A is for Artificial Insemination (AI)

Artificial insemination (AI) is the opposite to natural cover. 40 – 60mls of chilled semen is instilled into the uterus via a rigid hollow plastic tube or pipette past through the cervix. The much smaller volume of frozen semen can be delivered right to the tip of the uterine horn on the side of ovulation via a flexible mini-tube and stylet – see D below.

B is for Buserelin

A hormone injection that helps follicles grow. Also, when given at day ten after ovulation it reduces early embryonic death.

C is for Corpus Luteum (CL)

When a follicle bursts at ovulation it fills with luteal tissue to form the corpus luteum or yellow body. This produces progesterone which is the hormone that supports pregnancy.

 D is for Deep Intrauterine Insemination

We like to use a mini-tube pipette and stylet.

E is for Embryo

Sperm meets egg in the fallopian tubes. Combination of sperm and egg (fertilization) results in formation of an embryo.

 F is for Follicle

When we scan mares we are always measuring follicles. These are the fluid filled bodies within the ovary that contain an egg. When they reach 40-50mm in diameter they burst releasing the egg – this is called ovulation.

 G is for Genital Tubercle

At 62 days it is possible to sex the foetus by looking for the position of the genital tubercle.

H is for Hampton Veterinary Group

Hampton Veterinary Group has been successfully managing mares for AI for the last ten years.

 I is for Irrigation

At natural cover, debris including bacteria is introduced in to the uterus. A fit healthy mare expels this so that the uterus is a clean, safe haven for the embryo when is arrives from the fallopian tube at day five. AI is cleaner and far less debris is introduced. However, the concentrated semen and extender themselves cause inflammation of the uterus. Irrigation with two-three litres of sterile saline plus or minus antibiotics helps prepare the uterus for the embryo. This is a very important part of the AI process.

L is for Luteinising Hormone (LH)

This is a marvellous drug which has taken a lot of the work out of AI. When given to an in-season mare with a 35mm plus follicle LH will induce ovulation 36 hours later.

M is for midnight

Despite LH (see above) and “before midday” delivery times from Europe we still find ourselves scanning and inseminating mares at midnight!.

 N is for Nitrogen

Liquid nitrogen is used for keeping semen frozen. Canisters are topped up every six weeks by a contractor.

O is for Oxytocin

 Oxytocin is a wonderful drug that causes contraction of the uterine muscles. Naturally produced at foaling to expel the foal, given after cover or insemination, it clears fluid and debris and helps prepare the uterus for the arrival of the embryo.

 P is for Prostaglandin (Pg)

PG will only work on a Corpus Luteum which is more than six days old. A CL naturally disappears at about 16 days allowing the mare to come into season. Mares usually ovulate between four and ten days after and injection of PG.

Q is for quality of the semen

After every insemination we examine a spare drop under the microscope to check sperm are swimming actively and progressively and report back to the semen provider.

R is for Regumate

 Regumate is synthetic progesterone. Progesterone is the hormone that we can use to manipulate the oestrus cycle and to help maintain pregnancy.

S is for semen

Frozen semen can be stored indefinitely in canisters full of liquid nitrogen but only lasts eight hours inside the mare. Insemination must therefore occur within the eight hours either side of ovulation. Chilled semen lasts 48 hours in a chilled Equitainer. It lasts longer in the mare than frozen semen so the timing of insemination to ovulation is not so critical. Fresh semen does not survive any time outside the mare however inside the mare there have been incidences of conception occurring six days after cover!.

 T is for Twins

When two follicles burst releasing two eggs there is a high possibility of twins. Very occasionally a single egg dives to produce identical twins. Mares are not designed to carry twins. Most will naturally reduce to a singleton. If they continue to develop they are usually aborted or if they go to term are associated with dystocia with risk to the mare’s life. Consequently we tend to “pinch out” a twin at 15 days of pregnancy.

 U is for ultrasound

The use of the ultrasound machine has revolutionised the management of mares for breeding. Best used with the mare restrained in stocks it confirms what you can fel by per rectum palpation and allows you to see uterine fluid and early pregnancy including twins.

V is for Vet!

 W is for “Le Weekend”

French stallions tend not to be collected over the weekend. This means timing ovulation to occur mid week.



 Z is for Zimbabwe

Where Hampton vet, Rupert Gunstone back in 1995 was the first person to import and successfully inseminate local mares with frozen semen from the UK.