Ovine Observer

Pregnancy scanning increases profit for all flocks and times of lambing

John Young, Farming Systems Analysis Service Denmark, WA

Author correspondence:


Pregnancy status, number of fetuses and fetal age can be identified by ultrasound scanning. Previous economic analyses have drawn varying conclusions about the profitability of implementing pregnancy scanning on-farm (Bowman et al. 1989, Holmes and Sackett 2008, McGrath et al. 2016 and Young et al. 2016). Adoption of pregnancy scanning has been slow (Howard & Beattie 2018, Curnow & Conte 2018) and the surveys indicate that the single largest reason for not adopting is that producers “see no benefit”. Therefore, it was considered important to address the question of the on-farm benefit of pregnancy scanning with a comprehensive economic analysis.

Information about the pregnancy status of ewes (pregnant/not pregnant) can be used to:

  • Cull the ewes that are scanned empty prior to next joining. Reproduction rate (number of fetuses per ewe) is a repeatable trait so culling these ewes can increase reproduction of the remaining flock in subsequent years (Kleeman et al. 2016, Hatcher et al. 2018).
  • Reduce the feed offered to the empty ewes or sell them at scanning.

The additional information from scanning for multiples allows extra management adjustments:

  • Differential nutrition during pregnancy based on litter size. There are 3 drivers for the value of making this adjustment
    • Progeny survival (Oldham et al. 2011) and the total value of the progeny wool (Thompson et al. 2011) is more responsive to optimal nutrition for twin bearing ewes, hence extra feeding of the twin bearing ewes at the expense of the single bearing ewes improves flock productivity.
    • Single bearing ewes, particularly maternal breeds, if overfed during pregnancy can have birthing difficulties that leads to increased ewe and lamb mortality from dystocia.
    • Twin bearing ewes are more sensitive to under feeding in late pregnancy and can suffer from pregnancy toxemia, whereas this is only a minor problem for single bearing ewes.
  • Altering allocation of lambing paddocks based on litter size as twin born lambs are more sensitive to chill than their single born counterparts.
  • Incorporating information on birth type in the selection of replacement progeny for the breeding flock.

There are other benefits of pregnancy scanning that haven’t been included in this analysis:

  • The information from scanning can help to identify the points in the reproductive cycle where wastage is occurring, thus improving reproductive management.
  • Being proactive about reducing lamb mortality because fetus number is an essential piece of information to calculate lamb survival of single and twin born lambs.
  • Early detection of reproductive failure, which allows early remedial action such as remating or if the failure is due to a disease outbreak, providing earlier response for disease control.


To address the survey finding that a majority of farmers who currently don’t use pregnancy scanning do so because they “see no benefit”. We carried out a comprehensive evaluation of the profitability of utilising the information provided by pregnancy scanning for pregnancy status and for multiples for a range of regions, genotypes and times of lambing. We test the hypothesis that pregnancy scanning can increase farm profitability.


A wholefarm bio-economic model called the Australian Farm Optimisation model (AFO) was used to assess the profitability of management changes that can be implemented based on information provided by pregnancy scanning. AFO is a new and improved version of the MIDAS model. MIDAS has been used extensively in Western Australia to assess profitability of on-farm management decisions (e.g. Young et al. 2022).

AFO is an appropriate model to carry out this analysis because it incorporates both the biological and economic implications of altering livestock management. It includes a detailed feed budget that matches the feed requirement of animals throughout the year with the feed available from pasture, stubble or grain supplement. This allows optimisation of the nutrition profile of different classes of sheep while accounting for the change in production and the impact on stocking rate and supplement required.

The analysis was carried out for three regions with varying length growing seasons: a long growing season based on south-west Victoria; a medium growing season based on the Darkan area in the Great Southern of WA; and the short growing season based on the central wheat belt of WA. For each region, three lambing times (autumn, winter, spring) and three breed types (Table 1) were evaluated.

Table 1 A description of the flock types included in this analysis




A self-replacing Merino flock with emphasis on wool production. Wethers sold as either store lambs to other farmers (6 months) or as shippers (18 months).


A self-replacing Merino flock utilising surplus ewes (cast for age or surplus ewe hoggets) for first-cross lamb production sold as suckers (4.5 months). Merino wethers can be sold as Merino prime lamb or as shippers. The emphasis is on meat and wool production.


Composite ewes are mated to composite rams to produce composite lambs. Wethers sold as prime lambs (4-5 months), and the emphasis is on meat production.

The cost of scanning represented in the analysis included both the cost of the contractor and the labour cost associated with pushing the ewes through the scanning crate and the mustering that is required per mob (Table 2). If all labour was provided by casual labour, the labour cost varied between $0.31/ewe if scanning pregnancy status only. This increased up to $0.40/ewe when scanning for multiples.

The cost of casual labour was $256 per day ($32/hr all-inclusive for an 8-hour day). To reflect the competition for labour between the livestock and crop enterprises at seeding, the amount of casual labour that was hired depended on the timing of scanning relative to seeding.

Table 2 The assumptions used for the cost of contracting. Source of contract cost: Cousins Merino Services with more than 2000 ewes to scan.




The contractor



     Contract cost ($/hd)



     Travel ($/hd)



     Throughput (hd/day)



Farmer provided labour



     Yard work – labour units



     Cost per hd*






Other costs



     R&M on infrastructure and fuel



Total cost



* assuming that all labour is hired

The value of scanning was calculated by comparing farm profit if the flock was not scanned with a flock that was scanned. The comparison was carried out for flocks that were scanned for multiples or only scanned for pregnancy status. If the ewes were not scanned for pregnancy status, then all ewes of each age group had the same nutrition profile during pregnancy and lactation, and lamb mortality was estimated using a common chill index across all ewes. If ewes were scanned for pregnancy status, then the nutrition profile of the dry ewes was optimised separately to the pregnant ewes for the period from scanning through to the next joining. Also, the sale time of the dry ewes was optimised including options to sell the dry ewes at scanning or at the following shearing.

If the ewes were scanned to also identify multiples, then the nutrition profile of the single and multiple bearing ewes could be separately optimised. Twin bearing ewes were allocated to the better lambing paddocks and the single bearing ewes were allocated to the more exposed paddocks. The proportion of single and twin born progeny selected as replacements was adjusted to account for the expected difference in lifetime wool value and lifetime reproduction.

An allowance was made in this analysis for some discrepancy between the scanning results and the lambing outcome. Bunter (2020) showed an agreement between scanning results and mothering up results averaged 86% in the Sheep Genetics database including 68 360 records. In this economic analysis, allowance was made for all the discrepancy to be associated with scanning errors. This is a very conservative assumption with respect to estimating the value of scanning because Bunter (2020) observed that some of the errors would be due to assigning litter size at lambing and concluded this was the most likely source of discrepancy.

Sensitivity analysis was carried out to examine the impact of the proportion of ‘empties’ and ‘multiples’ in the flock; the average chill factor at lambing; the increase in reproductive rate expected from culling the passengers; and price of wool, meat and grain.

The differences in production and the responses to altering nutrition of the single and multiple bearing ewes was based on a synthesis of information from the Lifetime Wool research carried out in Western Australia and south west Victoria (Oldham et al. 2011, Thompson et al. 2011) and the CSIRO GrazPlan models (Freer et al. 2012).

Results and discussion

Value of scanning

Utilising the information from pregnancy scanning for multiples increased profitability for all 27 scenarios of region by genotype by time of lambing (Table 3). The average profit was $5.75 per ewe scanned and ranged from $1.20 up to $10.60 per ewe. This equated to a 400% return on the scanning investment. These results and the other benefits that have not been included in this analysis indicate that pregnancy scanning is likely to increase profitability for the majority of farmers.

The value of scanning was higher for flocks that were lambing in autumn and slightly less for flock lambing in spring. This difference in value associated with time of lambing is because the early lambing flocks are scanning and identifying the empty ewes prior to the main feed shortage, which increases the value of adjusting their nutritional management or from selling at scanning.

Table 3 The increase in farm profit from scanning for multiples and implementing optimum management ($/ewe scanned) for each of the 3 regions and 3 flock types for 3 times of lambing

Region & Flock

Time of Lambing







Long Growing Season













Medium growing season













Short growing season


















Overall average



Return on investment: 400%


Management changes required to capture the benefits of scanning

In order to capture the potential benefits of scanning, it is necessary to implement management changes for the ewes scanned with different pregnancy status and litter size. Each of the management changes are associated with capturing a portion of the potential profit (Table 4). The contribution of each management component varied across the scenarios. On average about half the total value could be captured if the ewes were scanned only for pregnancy status and it was necessary to scan for multiples to capture the full benefits.

The biggest single contributor to profitability of scanning for multiples was selling the passengers to increase subsequent reproduction in the flock (Table 4). The other management components each made a similar contribution to the total value of scanning.

The comparison between selling ‘once dry’ or ‘twice dry’ ewes showed that selling ‘once-dry’ was more profitable for the flocks that can maintain flock size with this higher level of culling. This should be achievable for flocks that have a weaning percentage greater than 90%. For flocks with a lower weaning percentage, selling ‘twice-dry’ was best. The best time to sell is a trade-off between the feed that can be re-directed as a result of selling the empty ewes early vs the wool production that is foregone by having fewer animals during the spring flush. For maternal flocks and Merino flocks that are scanning prior to the main feed shortage, selling at scanning is usually most profitable.

Table 4 The contribution of each management component to the value of scanning and whether that component is possible based on the level of scanning undertaken



Pregnancy status

Value ($/ewe)

Sell the passengers


Feed allocation



    to pregnant ewes


    to multiples


Paddock allocation


Replacement selection


Capturing the benefit of altering feed allocation requires adjusting the condition score targets for empty, single-bearing and twin-bearing ewes. If the ewes are not scanned, then at lambing the empty ewes will typically be 0.5 CS higher than the single bearing ewes, and the twin bearing ewes will be 0.5 CS lower. If the ewes are scanned for litter size, the optimum profile is to have the empty ewes that are retained 0.5 to 1.0 CS lower than the single bearing ewes and the twin bearing ewes 0.3 to 0.5 CS higher at the point of lambing. At weaning, the target is to have the empty ewes with a CS similar to the twin bearing ewes, which will be similar or slightly less than the single bearing ewes.

To capture the potential benefit associated with paddock allocation requires identifying the better lambing paddocks and allocating the twin bearing ewes to these paddocks and the single bearing ewes to the poorer, more exposed paddocks. During lactation the twin bearing ewes have higher energy demand, so managing these paddocks to achieve a higher FOO at lambing is also beneficial.

To capture the benefit of adjusting the selection of the replacement ewes requires identifying the progeny as either single or twin born and being able to separate on birth type when the replacement ewes are being selected. The optimum proportion of singles and twins to select was not quantified in this study, but it has been observed on farm that if the twin born progeny have not been identified they will be selected against because they are smaller than their single born counterparts. It is expected that biasing the selection towards the twin born progeny will improve long term profitability, especially for flocks that have more focus on meat production than wool production.


Changing wool prices and grain prices across the range of price scenarios examined had little effect on the value of scanning (Figure 1). This is because adopting scanning has little effect on the total quantity of wool produced, and the adoption of scanning and the change in ewe nutrition profiles does not have a consistent effect on the total quantity of supplement fed. In contrast, varying the meat price did alter the value of scanning (Figure 1) because the quantity of lamb produced is increased. Altering the meat price scenario down to the 50th percentile ($4.65/kg DW for lamb) and up to the 90th percentile ($6.70/kg DW) altered the value of scanning by plus or minus 30% on average. The range of lamb price that is associated with the percentile change is plus and minus 18%, so the value of scanning changes by a greater proportion than the lamb price.

Extrapolating the results of this analysis would indicate that lamb price would have to drop by 60% to $2.50/kg for the average profitability of scanning to drop to zero. So, although the profitability of scanning is sensitive to meat price, the likelihood of scanning becoming unprofitable is low.

Graph showing the Total value of scanning for multiples against price percentile
Figure 1 Impact of altering meat price (►), wool price (l) and grain price (♦) on the value of scanning for multiples averaged across the 27 scenarios of region, flock and time of lambing

Flock reproduction rate

The reproductive rate of the flock has very little effect on the total value of scanning for multiples (Figure 2); the change in the value of scanning if the reproductive rate is below 100% to above 175% is less than $1.50 per ewe scanned. However, across this range, the benefit shifts from being predominantly associated with managing the empty ewes to being predominantly managing the multiple bearing ewes.

Graph showing the value of pregnancy scanning against reproductive rate
Figure 2 The value of pregnancy scanning for multiples is not sensitive to the reproductive rate of the flock, although the contribution from managing the empty ewes or managing the multiple bearing ewes changes across the range

Key messages

  • Pregnancy scanning is low-cost with a high return on expenditure.
  • Pregnancy scanning for multiples increased potential profit in all the scenarios examined, with an average increase of $5.75/ewe scanned.
  • Scanning for multiples was twice the value of scanning for pregnancy status only.
  • Capturing the potential profit requires implementing some management changes to utilise the information provided from scanning.


Funding for the L.LSM.0021 Project ‘Increasing lambing percentages through better use of pregnancy scanning technology’ was provided by Meat and Livestock Australia and Australian Wool Innovation Limited. The project was led by Associate Professor Forbes Brien of The University of Adelaide, SA.


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