It’s no secret that I’m somewhat passionate about reducing mob size at lambing, after spending a few years completing my PhD on the topic. Research from my PhD and subsequent work with triplet-bearing ewes has shown that smaller mobs at lambing increase lamb survival – on average, reducing mob size at lambing by 100 ewes increases the survival of single-, twin- and triplet-born lambs by 0.8%, 2.2% and 15.1%. You can find three papers covering the impacts of mob size at lambing on lamb survival and the economic value of lambing ewes in smaller mobs, including the costs of paddock subdivision, at my earlier post on The Hub: https://thehub.nextgenagri.com/c/shepherd-share/lambing-ewes-in-smaller-mobs-to-increase-lamb-survival.

After reading through the results of the economic analysis, you will understand why we can’t provide generic recommendations for the optimum mob size of ewes at lambing – because there are several enterprise-specific factors influencing optimum mob size and the profitability of paddock subdivision, such as breed, stocking rate, lamb price, scanning percentage and the target return-on-investment. I think it would be great if a decision-support tool could be developed where you can plug in data specific to your enterprise to determine the optimum mob size for your ewes and the profitability of subdividing certain paddocks on your farm. This could also incorporate factors like feed-on-offer and pasture quality, to help with broader decisions associated with allocating ewes to lambing paddocks to optimise ewe and lamb survival.

Is temporary paddock subdivision the answer?

Lambing ewes in bigger mobs means there is a greater number of ewes lambing per day and more lambs born per day, particularly in multiple-bearing mobs. Many producers will agree that this can create chaos, including an increased opportunity for mismothering. In mixed sheep and cropping enterprises, particularly in the wheatbelt of Australia where stocking rates are lower, larger paddocks are more practical and efficient for the cropping enterprise. In these businesses, sheep are often used to utilise crop residues and help control summer weeds and hence they may not be the main focus. Some producers may also prefer larger paddocks to allow larger mobs to be grazed during other times of the year.

Hence, for a variety of reasons, some producers still choose to lamb ewes in larger mobs because they don’t have smaller paddocks available to split lambing ewes into and/or they don’t wish to permanently subdivide paddocks for fair reasons. Temporary subdivision of paddocks may provide a solution in these circumstances.

Economic analysis has shown that, in many scenarios, it is profitable to subdivide paddocks to lamb ewes in smaller mobs. Permanent subdivision of paddocks provides the added advantage of increasing pasture utilisation, enabling higher stocking rates and profitability over the long term. However, subdividing paddocks with temporary fencing is often highly cost effective and this may be an option to achieve the benefits of subdivision without affecting other enterprises within the business.

What else should you consider?

Note that this list is not exhaustive.

Historical performance 

Which paddocks perform the best each year for lamb survival? Subdividing these paddocks could better utilise these areas for lambing more of your higher risk ewes (i.e. multiple-bearing and those in poorer condition).

Shelter and other paddock characteristics

Could the resulting characteristics of the lambing paddocks counteract the benefits of being able to lamb ewes in smaller mobs?

For example:

• How much shelter will there be in the subdivided paddocks? Will subdivision result in one well-sheltered paddock and one without any shelter, where ewes and lambs are unable to seek protection from adverse weather? Shelter is particularly important for high-risk mobs (e.g. ewes that are multiple-bearing or in poorer condition and their lambs). 
• What will be the aspect/s of the resulting paddocks? Paddocks facing the prevailing winds increase the risk of exposure for newborn lambs.
• What will be the topography of the subdivided paddocks and will this change grazing or camping behaviours, potentially resulting in some eroded areas of the paddock, etc?
• Paddock layouts which enable shorter subdividing fences will reduce the cost of subdivision and increase profitability. 

Water availability 

Will subdivision result in a paddock/s without access to water? 

• If you lamb later and seasonal conditions are good, ewes may have little need for water sources because green feed may supply enough to meet their needs (although access to water is still recommended). However, if you lamb earlier in autumn or at the break of season, or if seasonal conditions are poor, access to water will be very important. 
• If water in the paddock is supplied by a dam, could the paddock be subdivided to allow dual use of the dam, saving the need to add a trough? If you’d need to add a trough, can the paddock be subdivided in a way to reduce the distance between watering points, saving money?
• Ensuring that water sources are of acceptable quality is also important.

Feed availability and quality

Are there areas in the paddock that grow less feed or have poorer quality feed? Can the paddock be subdivided to optimise access to enough good quality feed in both/all of the resulting paddocks? Feed availability and quality are key factors influencing the performance and survival of lambing ewes and their progeny, so ensuring that paddock subdivision does not compromise nutrition is very important.

Fencing materials

• If using temporary electric fencing, how many hot wires should you use? This will depend on factors including the familiarity of your sheep to electric fencing along with the amount of feed-on-offer, but I’ve heard of many producers using two or three hot wires (or even just one) with success. 
• Do you have some spare or recycled ringlock and star pickets lying around that could be put to use? If only a short temporary fence is needed, a temporary ringlock fence could be an option. 
• Learn from those already using temporary fencing with success (or not) – a neighbour or friend perhaps? Are you reading this article and have wisdom to share? Post it on The Hub!

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Improving lamb survival is a passion of mine and I’m pretty confident that most sheep producers would place improving lamb survival high on their list of priorities, for both animal welfare and profitability. There are many factors that influence lamb survival and hence implementing an array of tactics is important to make progress. Grab the low-hanging fruit first (i.e. ewe nutrition during pregnancy and lactation) and then work on those tactics that shift you a few percent higher with lamb survival, like reducing mob size at lambing. What will you change this year to help lift your lamb survival results?

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Head to the neXtgen Agri Hub to share your thoughts and ask any questions about reducing mob size at lambing.