It is useful to consider the following when embarking on either an AI or ET programme.
Laparoscopic artificial insemination
Ewes are synchronised using intravaginal sponges and PMSG so that they all ‘come on heat’ together.
46 hours (fresh semen) or 53 hours (frozen semen) after sponges are removed, the ewes are sedated and semen is injected directly into the uterus using keyhole surgery.
The dose of semen required is 20 million, progressively motile (forward swimming), spermatozoa but in practice higher doses are often used. A donor ewe for embryo transfer, will usually receive a minimum dose of 100 million.
Multiple ovulation and embryo transfer
Hormone injections are used to help donor ewes to release large numbers of ova or eggs which are fertilised using artificial insemination.
Five days later the resulting embryos are collected surgically, under general anaesthetic and transferred to surrogate (recipient) ewes or frozen and stored in liquid nitrogen.
Recipient ewes should be in good condition too to make sure that they hold implanted embryos and carry them successfully to term.
Progesterone impregnated sponges are placed intra-vaginally in ewes.
The sponges allow follicles to develop on the ovaries but prevent ovulation.
Hormone injections are given to stimulate follicles to form.
A large number of follicles develop and grow on the ovaries and are then held in a kind of suspended animation.
All of the follicles ovulate at the same time and eggs (known as ova) are released into the fallopian tubes.
The ova are fertilised and become embryos.
Embryos are collected under general anaesthesia (flushing) and implanted into surrogate or recipient ewes. You should be aware that as with any surgical procedure, there are recognised risks, although the incidence is extremely low.
Semen collection and freezing
For semen freezing, rams visit our centre and are trained to jump teaser ewes so that semen samples may be collected. This can take a varying amount of time but once trained, rams do not usually forget how to be collected.
Very occasionally some rams may not learn to ‘jump’. In this situation and with your permission they may be electro-ejaculated. Samples produced in this way can be of lower quality and so it should not be relied upon as a method of semen collection for an AI day. However, it can be used to assess fertility and may allow backup semen to be frozen.
Semen is graded on a scale of 0 to 5, where 5 is top quality. Only semen graded as a 4 or a 5 is processed for freezing but even where fresh semen is of excellent quality, semen freezing is not always successful. Two to three jumps are taken each day on centre and the semen is diluted and frozen, using dry ice and liquid nitrogen.
Once frozen, a sample pellet or straw from each batch is thawed and assessed under a microscope. If over 30% of spermatozoa are swimming strongly forward (progressively motile) and no major abnormalities are present, then it has passed and is stored. Where semen does not meet this standard, unfortunately it is destroyed, as it is not of good enough quality to be used.
The process can be quite variable and a ram’s semen may pass on some days and not others. The semen may increase in ‘freezability’ during his stay or it may decline. We shall keep in close contact with you whilst your ram is here so you know how the process is progressing.
Occasionally where semen freezing is proving unsuccessful, a ram will be sent home but may be returned after a few weeks. You should not feel discouraged as this is perfectly normal. In most cases however the process will be completed within a few days. The length of time the ram needs to stay on centre depends on how many doses of semen you require but a ram which jumps straight away, should only take a two or three days to give around 50 doses.
To optimize the freezing process, rams should be in good body condition and good health. They should not have been out with ewes for at least two weeks.
Semen freezing is excellent insurance against loss of use and there are no charges for the first year of storage at our facility. If you need any fertility advice do not hesitate to contact us for further information.