Are you joining ewes before Australia day and finding them slow to start lambing?
Are you joining ewe lambs and finding the same problem, or that your conception rates could be better?
If so, you are likely witnessing the results of the ram effect, and you can take advantage of this!

When joining out of season exposing your ewes to teasers prior to joining can improve conception rates, but more importantly can get more lambs on the ground earlier in the season. Not only does this make management practices like lamb marking, pasture management and worm control easier, it will set you up to make more money! If a lamb hits the ground 17 days (1 cycle) earlier and achieves an average daily gain of 300g, that will correspond with approximately 5kg of extra live weight. At a conservative $3 / kg LW, that could equate to an extra $15 per lamb.

So how does it work? Sheep are seasonal breeders, with reproductive activity peaking in Autumn as triggered by a shortening day length. Prior to the summer solstice, or up to mid-February for British bred sheep, ewes will experience seasonal anoestrus where they are not cycling regularly. During this period, exposure to a ram will evoke the ‘ram effect’ – resulting in ovulation 2-5 days later. This will however be a silent heat, meaning the ewe will not display signs of oestrus or actively seek out the ram. Following this ovulation they will return to a regular cycle, but consequently you will get very few lambs in the first 17 days of joining. Taking advantage of this ram effect is a simple way to maximise productivity and profitability. It is obviously still important to ensure that condition score and feed availability are not limiting factors.
There are a couple of options when it comes to using teasers, in the form of wethers treated with testosterone or vasectomised rams. In all cases, teasers are run with ewes for the 14 days immediately prior to the joining period, and must be removed when the rams are introduced to avoid competition. To be effective, ewes need to have been kept separate from rams and teasers leading up to this time, ideally by at least 1km for at least 4 weeks.

Wethers treated with testosterone will typically require 2 injections prior to use, and will not be able to enter the food chain following treatment due to withhold concerns from hormone treatment. Depending on the breed, age and size of wethers used, they will be required at a rate of 1-4%.
Vasectomised rams are increasing in popularity, with no concerns of hormone treatment and less labour required leading up to joining. Whilst a somewhat specialised veterinary procedure, the vasectomy surgery is relatively quick and non-invasive and obviously lasts the life time of the ram. Many people will retain some ram lambs to be vasectomised and used as teasers, purchase cull rams from the same stud they are purchasing rams from or purchase merino rams for the role to take advantage of a wool cut and ensure they are easily identifiable. Vasectomised rams will be required at a rate of 1% when mature and anecdotally are achieving better results than testosterone treated wethers.

If you would like to explore the possibility of using teasers in your operation, get in touch with your vet. They will be able to discuss the benefits and develop the most cost-effective plan for your operation.

Author: Jo Ward – Livestock Vet
2274 Coleraine Edenhope Rd COOJAR VIC 3315
joward@livestockvetservices.com.au
M: 0439 826 190