Join rams with ewes for five weeks (i.e. two, 17-day cycles). If joining ewes outside the peak breeding season (before January or after June), use teasers to stimulate oestrus in ewes that aren’t cycling spontaneously. Most ewes get pregnant in two cycles.
On more intensively run farms, extending the joining for longer periods is not recommended because the 2-4% of extra lambs born delays completion of important management events, such as marking and weaning. Delaying weaning for a few late lambs can result in serious worm burdens leading to weight loss in both ewes and lambs.
In winter-lambing Merino flocks, the late lambs generally have poor survival rates, because they have a lower bodyweight during summer. Late weaning compromises ewe condition recovery when preparing for the next reproductive cycle.
What if ewes fail to get in lamb?
When joining during the peak breeding season, at least 90% of Merino ewes and up to 98% of crossbred ewes get pregnant in the first two cycles. Pregnancy rates can be 10% lower if joined outside the normal breeding season.
If more than 15% of ewes are not pregnant in the target joining time, work with an experienced animal advisor to determine the reason.
Both ewes and rams can contribute to poor conception rates. The most common causes are low condition score, poor nutrition or ram health. Consider pasture toxicities, including syndromes such as perennial ryegrass toxicosis or oestrogenic clover infertility.