Improving conception, scanning results and lamb survival
Improving conception, scanning, and lamb survival is a multi-faceted game that begins months before the rams go out. This guide outlines the critical links between pre-joining nutrition, mating duration, and pregnancy management, providing Western Australian woolgrowers with a roadmap to optimise ewe energy reserves and lift whole-flock productivity through the challenging summer-autumn period.
When flock performance is discussed, attention often turns to lambing and weaning. These are highly visible points in the production cycle, but by the time lambs hit the ground, most of the factors influencing conception rate, scanning percentage and lamb survival are already locked in.
Decisions made months in advance regarding nutrition, timing and management establish the foundation for a flock's ultimate performance. Getting these fundamentals right doesn’t require complicated systems, but it does require planning, consistency and using available information to guide decisions.
Conception is driven by preparation
Ewe conception rate is heavily influenced by nutritional status in the lead-up to joining. Ovulation rate responds to a rising plane of nutrition, not just the amount of feed on offer.
Condition scoring remains one of the most reliable and low-cost tools available to assess this. It is a direct measure of the energy reserves a ewe is carrying and one of the strongest predictors of reproductive performance. For merino flocks, a target condition score of 3 at joining is ideal. Young ewes, maidens and ewes coming off a tough season often require additional support to reach this target.
Accurate condition scoring matters. Scoring sheep properly in the yards, rather than visually or from the ute, allows woolgrowers to identify ewes that need attention early, rather than reacting once performance has already been compromised.
Key considerations before and during joining include:
- Assessing condition score six to eight weeks before joining
- Identifying lighter ewes early and preferentially managing them
- Avoid sudden feed changes in the final weeks before joining
- Ensuring ewes are gaining or at least maintaining condition through joining
Ewes that are losing condition during joining will generally have lower conception rates, even if they appear acceptable when visually assessed. Once ovulation rate is compromised, it cannot be recovered later in the season.
Joining length and timing matter
Joining length and timing are two of the most influential decisions in a sheep enterprise, yet they are often based on habit rather than deliberate planning. The choices made at joining define not only when lambing occurs, but also lambing spread, peak nutritional demand, weaning dates, lamb age variation and the recovery window before the next joining.
Extending joining beyond five weeks can deliver diminishing returns. Longer joinings typically result in only a small increase in lamb numbers while creating a wider lambing spread. Later-born lambs are often younger at marking and weaning, have less opportunity to perform and can complicate management by extending lambing and creating uneven mobs.
Given that ewes cycle approximately every 17 days, a 35-day joining provides two full opportunities for conception. In well-prepared flocks with fit, fertile rams, this is generally sufficient to achieve conception rates above 95 per cent. Tighter joinings also make it easier to target nutrition and management to ewes based on their stage of pregnancy and lactation.
The timing of joining is equally important. Joining date determines when nutritional demand peaks and how well that demand aligns with pasture growth. Sheep are seasonal breeders, with cycling activity increasing as day length shortens. In the WA Mediterranean climate, ewe responsiveness typically peaks in autumn, particularly through March and April. Later joinings may improve conception, but they also push lambing closer to the end of the pasture growing season, increasing pressure on lamb growth and finishing.
Where joining occurs earlier or out of season, strategies such as nutritional flushing or the use of teaser rams may be considered to stimulate cycling and tighten conception. Teasers are most effective when ewes are already on a rising plane of nutrition and should be used as part of a broader joining strategy, not as a substitute for good preparation.
There is no single ideal joining date that suits every business. The most profitable systems are those that match ewe nutritional demand to pasture growth, allow sufficient time to grow lambs out effectively and fit within broader farm workloads. Planning tools, such as the Department of Primary Industries and Regional Development Lambing Planner, can assist by working backwards from lambing to joining and visualising lambing spread, feed demand and labour requirements across the season.
Nutrition in pregnancy sets lamb survival outcomes
High scanning percentages only add value if lambs survive to weaning. Late pregnancy and early lactation are the most nutritionally demanding periods for a ewe, with around 70 per cent of foetal growth occurring in the final six weeks before lambing.
Common risk periods for nutritional deficiency include:
- Late summer and early autumn joinings, where feed quality is declining
- Situations where pasture bulk appears adequate, but energy or protein levels are limiting
- Sudden cold, wet or windy weather that increases maintenance requirements
Ewes that lose condition during late pregnancy are more likely to experience pregnancy toxaemia, lower lamb birthweights, poorer mothering ability and reduced milk production, all of which increase lamb mortality risk.
Managing by pregnancy status delivers returns
Once pregnancy status is known, how ewes are managed becomes critical. Separating single and twin-bearing ewes remains one of the most effective tools available to improve lamb survival.
The nutritional demands of twin-bearing ewes are significantly higher than those carrying a single lamb, particularly through late pregnancy and early lactation. Managing singles and twins together often results in twin-bearing ewes being underfed, even when overall feed availability appears adequate.
Even modest differences in feed allocation between single- and twin-bearing ewes can result in:
- Higher lamb survival
- Heavier lambs at marking and weaning
- Better ewe recovery post-lambing
- Improved rejoining performance in the following season
Importantly, these gains are often achieved through better targeting of existing feed resources rather than increasing total feed inputs. Where full mob separation is not possible, prioritising twin-bearing ewes for higher-quality paddocks, access to shelter and targeted supplementary feeding can still deliver meaningful improvements.
Lamb survival is influenced by more than feed
While nutrition is critical, lamb survival is also influenced by management and environment.
Key factors include:
- Lambing paddock selection and shelter
- Mob size at lambing
- Weather exposure
- Ewe condition and behaviour
- Timing of lambing relative to feed availability
High stocking pressure in lambing paddocks increases the risk of mismothering and lamb losses, particularly in twin mobs. Matching mob size to paddock size and shelter availability is an important and often underestimated management lever.
Scanning results are feedback on management
Pregnancy scanning provides valuable information, but it is most useful when treated as feedback rather than an endpoint. Scanning percentage reflects nutrition before and during joining, ewe health and parasite burden, joining management and seasonal conditions at conception.
Looking at scanning trends across years is far more informative than reacting to a single poor result. Consistently lower-than-expected scanning percentages usually point to repeatable management constraints rather than bad luck.
Using data to drive better decisions
Pregnancy scanning data becomes far more powerful when combined with condition scoring, paddock history and basic production records. On its own, scanning shows what happened. Combined with other information, it helps explain why.
Reviewing results with a few targeted questions can quickly highlight opportunities for improvement:
- Are twin-bearing ewes losing condition in late pregnancy?
- Do some paddocks consistently record lower lamb survival?
- Are later-joined ewes underperforming earlier-joining mobs?
- Is lamb survival reduced following shorter joinings in tougher seasons?
Paired with electronic identification (EID), this type of analysis becomes significantly more powerful and reliable. EID allows individual ewes and lambs to be tracked across joining, scanning, lambing and weaning, supporting more precise decision-making and better targeted management changes across seasons.
Small improvements compound quickly
Improving conception, scanning results and lamb survival rarely comes from one major change. It comes from stacking small, achievable improvements across nutrition, timing and management.
A one per cent lift in conception rate, a small improvement in scanning percentage or one extra lamb per hundred ewes weaned compounds quickly across the flock and across years.
By focusing on preparation before joining, protecting ewe condition through pregnancy and using scanning data as feedback and making management changes accordingly, WA woolgrowers can lift whole-flock performance over time.
For more information, check out the following resources used throughout this article:
- Making more from sheep - Module 10 Wean More Lambs
- Lifetime wool - Management handbooks and case studies
- AWI Joining article
- Lambing Planner - DPIRD tool
Phoebe Eckermann, AWI Extension WA
