A compact lambing period is the ultimate goal on many sheep farms; however, in some cases, it is sometimes hard to achieve.

One way to possibly tighten up the lambing period is through the use of the ‘ram effect’.

According to Teagasc, the ‘ram effect’ can be used to induce ewes or ewe lambs to start cycling provided that they are sufficiently close to the time period of the onset of normal cyclicity.

In order for the ‘ram effect’ to work, ewes should not be in contact (either sight, sound or smell) with rams for at least 28 days.

The reason for this is because when ewes are exposed to rams again, the rams’ pheromones cause hormonal changes in the ewe that initiate cyclicity.

Teagasc says that upon introduction of adult rams, most ewes that are not already cycling will have a ‘silent heat’ within 36 hours and a proportion will have a second silent heat after six days. These ‘silent heats’ are not detected by rams.

It is recommended to remove rams after 24-36 hours. Ewes should then cycle approximately 17 days after the final silent heat.

The event of a first heat (detectable by rams) will be 18-23 days after ewes have been exposed to rams.

It is advised that fertile rams be introduced to the flock 14 days after the rams were first introduced, in order to pick up any short cycles or to pick up any ewes that were already cyclic at the time of ram introduction.

When using the “ram effect” to synchronise the mating season, it is also recommended to have an adequate number of rams for mating – ideally, one ram per about 18 ewes.

Furthermore, it is essential to have adequate facilities – especially lambing pens (one pen per six ewes) and labour – in order to cope with the increased workload that comes with a compact lambing period.

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