Teaser Rams have been vasectomised i.e. a section of their vas deferens (tube carrying semen from testicle to urethra) is removed and the ends tied off. This means that the tup still produces testosterone, has the urge to mount and emits pheromones but ceases to produce fertile semen.

Introducing teaser tups in the transitional period of the ewe’s natural season will have the effect of encouraging the ewes to cycle earlier than usual.

Teasers should have excellent libido and be a compatible breed for the time of year their use is intended. They should be carrying plenty of condition before they are introduced (CS 3.5) and should have a full MOT (feet, worms, insecticide, multivits.) in plenty of time prior to introduction. 

Use of Teasers in an AI Programme

Ewes should be weaned and separated completely from sight and smell of a tup for 4-6 weeks prior to the introduction of teasers in order for this ‘ram effect’ to work. The teasers are then introduced, ideally at a ratio of 1:25 ewes and remain with them for 2-3 weeks. The sponges are then inserted and the teasers removed. When the sponges are removed the teasers are re-introduced with raddle on. This enables the AI operator to assess how well the ewes have responded and also to avoid using expensive frozen semen in unmarked ewes. Extremely high conception rates can be achieved if only marked ewes are inseminated.   

Use of Teasers in Natural Breeding

Ewes are weaned and kept separate from any males for 4-6 weeks. The teasers are then introduced for 2 weeks only. The teasers are then replaced with entire rams at a ratio of 1:25 ewes. 40-60% of ewes will have a fertile oestrus about 18 days from the introduction of teasers. The rams can be left in however the preferred method is to leave them in a week with one colour raddle on, take them out for a week, then reintroduce them with a different colour raddle on. In commercial ewes one can leave the ram in for a second period of 2 weeks and then remove him completely. One would then cull any barreners at scanning time. With pedigree sheep one would probably just leave the tup in on the first or second occasion depending whether a break in lambing was required.  

MOET- this involves super-ovulating an individual ewe (the DONOR), inseminating her, and collecting the resulting embryos. The embryos are then transferred into RECIPIENT or surrogate ewes. The procedure can be carried out several times in one season, and can also be successful out of season due to the effect of the drugs used. The resulting embryos can be frozen for transfer at a later date or transferred ‘fresh’.  

MOET can be used to make rapid genetic gain by increasing selection intensity on the ewe side of the equation. Frozen semen can also be used for the insemination. Using frozen semen with MOET leads to a greater lamb crop per dose of frozen semen used.

MOET can also be used as a treatment for infertility. The super-ovulatory drugs, and the stage at which the embryos are taken means that several forms of infertility can be avoided.

MOET especially comes into its own when aged ewes which may have a damaged mammary gland, or who are unable to carry or rear lambs for a variety of other reasons, can be taken out of production and given a ‘rest’. The embryos she produces can be transferred into younger, fitter, healthier ewes giving the lambs a much better chance of survival.

Success of MOET in sheep can be variable just as it can in other species. Factors such as breed, season, age, condition and certain genetic differences all combine to produce variability in results. Different ewes respond differently and the same ewe flushed several times can respond differently.

Embryo Freezing - embryos can be frozen in liquid nitrogen, in a similar manner to semen. This facilitates transfer of genetic material both within and outwith the UK. This allows access to markets otherwise difficult to reach for British pedigree sheep farmers.  

Ovum Pick-Up (OPU) and In-Vitro Fertilisation (IVF) - this has been utilised in other species including humans and cattle to great success. It avoids major surgery and allows a much greater potential harvest of eggs/embryos. This technique is not currently available, but we hope it will be in the near future.

In sheep the eggs are harvested from the ovary using a laparoscope in a live animal or taken from the ovaries recovered from a cadaver. The eggs are matured and fertilised in a lab and the subsequent embryos transferred to recipient ewes as described previously. Unlike conventional embryo recovery, eggs can potentially be collected on a weekly basis and no super-ovulation is required.