How Teaser Rams Work
All male sheep produce naturally occurring chemicals known as pheromones. These pheromones are detected by ewes and trigger a hormonal response. Often referred to as the “ram effect”, this response can be used to influence both the timing and synchronisation of the breeding season within a flock.
Under natural conditions, ewes begin cycling at different times as daylight hours decrease in autumn. This can lead to a more spread-out mating and lambing period. By carefully managing when ewes are exposed to rams, breeders can use the ram effect to encourage a more compact and synchronised breeding season.
If ewes are kept away from sexually active males for at least 6–8 weeks after weaning, with no contact through sight, smell or physical interaction, introducing a ram will stimulate hormonal activity. Most ewes will ovulate around six days later. This first ovulation is often a “silent heat”, where the ewe ovulates without showing obvious signs of oestrus.
A vasectomised ram, commonly known as a Teaser Ram, is a practical and cost-effective way of making use of the ram effect. Teaser rams help ewes cycle earlier in the season, leading to tighter breeding and lambing periods and making flock management easier.
When creating teaser rams, suitable males should be selected and prepared well before the breeding season. Following vasectomy, teaser rams should undergo fertility testing around 6–8 weeks after surgery to confirm that no viable sperm remain. Annual re-testing is strongly recommended to ensure the ram remains suitable for use and to avoid accidental pregnancies.
Using Teaser Rams in AI and ET Programmes
Teaser rams are widely used in Artificial Insemination (AI), Embryo Transfer (ET) and natural breeding systems. Their main role is to stimulate and synchronise oestrus activity, helping improve breeding outcomes and conception rates.
Artificial Insemination Programmes
For AI programmes, the following protocol is recommended:
- Introduce teaser rams to the ewe group approximately three weeks before sponge insertion.
- Ideally use one teaser ram for every 25 ewes.
- Remove teaser rams when vaginal sponges are inserted (Day 10).
- Remove sponges and reintroduce teaser rams on Day 12 to assist with heat detection and stimulate oestrus.
Using teaser rams before and during synchronisation programmes can improve ewe responses to hormonal treatments and help achieve more consistent results.
Embryo Transfer Programmes
In ET programmes, teaser rams are particularly useful for identifying the onset of oestrus in both donor and recipient ewes.
As with AI programmes, a ratio of one teaser ram per 25 ewes is recommended.
As a general guide:
- Introduce teaser rams to recipient ewes 24 hours after sponge removal.
- Introduce teaser rams to donor ewes 12 hours after sponge removal.
Accurate heat detection is essential for successful embryo transfer, and teaser rams remain one of the simplest and most reliable ways of monitoring oestrus activity. Heat detection should always be carried out in line with your ET protocol.
The Ideal Teaser Ram
A good teaser ram should be capable of serving and identifying up to 25 ewes within a 24-hour period. Careful selection and management are key to achieving this.
The ideal teaser ram should:
- Be healthy, sound and in excellent body condition. In many cases, teaser rams need to be fitter than entire breeding rams because of the level of activity expected during the breeding season.
- Come from a breed with strong breeding activity during the period in which it will be used. For example, Dorset rams are often well suited to early-season breeding programmes because of their extended breeding season.
- Be neither too young nor too old. Ram lambs that have been vasectomised are generally best used as shearlings once fully mature.
- Have the same health status as the resident flock and be up to date with vaccinations, parasite control and disease screening.
- Show strong libido and active mating behaviour to ensure effective heat detection within the ewe group.
Good year-round management of teaser rams will ensure they are ready for use when needed and performing at their best during the breeding season.
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