Lambmarking check for breech strike susceptibility

If you’ve thought about stopping mulesing, then the message from the AWI Breech Strike R&D Technical Update was that the following scores were required to have the same risk of breech strike as that of mulesed sheep:

  • Breech wrinkle score 2
  • Dag score 2
  • Breech cover score 3  

A decision to stop mulesing requires planning for management, breeding, chemical and marketing strategies: don’t just stop mulesing. Breeding needs to remain balanced for a profitable Merino and, like all major farm decisions, the whole business needs to be on board.  

For those regions that are currently undertaking lamb marking, take this opportunity to assess your lambs. At this lamb marking, do a count of breech strike-susceptible lambs.

There’s no need for recording or extra labour, just a few minutes preparation and some thought when the tails are done is all that is needed. 

Breech wrinkle and dag score are the most important factors in breech strike and breech cover becomes more important at higher wrinkle scores. Research is being conducted to better understand the importance of urine stain. Dag is not an issue in all regions. In these regions, standardized breech wrinkle scores can be used quite easily to assess your own sheep to give a very good indication of their susceptibility to breech strike.

Lambs with a breech wrinkle score of 1 or 2 rarely get struck, whereas those with a score of 4 and particularly 5 have a high chance of being struck.

Assessment for breech wrinkle is described below, but a similar process can be used for breech cover at marking. Dag score would best be done at a crutching or other management time; the groupings could be recorded in a variety of ways, such using a shearers counter, a chalk or crayon mark on the shed wall or crutching tailer or a run along a few race-fulls with pen and paper.

Figure 1. Breech wrinkle scores for lambs. Source: Sheep Genetics
Figure 1. Breech wrinkle scores for lambs. Source: Sheep Genetics

Flocks (where dag is not a major cause of breech strike) that have an average breech wrinkle score of 2 should expect few breech strikes in unmulesed sheep (without chemical prevention). Each year, these flocks produce only a few percent of score 4 or 5 lambs, which ideally should be culled.

Before lamb marking, print out the scoring picture (above) and tape it to the lamb marking cradle for quick reference.

If you use rubber rings to dock tails, tape two ice cream containers to the cradle near the rings—label one 1–3 and the other 4–5, representing wrinkle scores. Before the sheep are mulesed (if done at marking) and the tail is docked, score the breech wrinkle for the lamb. Toss a rubber ring into one or other of the ice cream containers according to the wrinkle score (you can still use these rings later after assessing a sample of the lambs).  

Alternatively, if your lambs have their tails taken off, toss the tails one side for any sheep that are score 1, 2 or 3, and to the other side for score 4 and 5. Count up the rings or tails and calculate the percentage of lambs that fall into these two groupings.

You don’t need to do this for the whole drop—ideally about 10% of the mob or at least 50 lambs. Practice with the first pen of lambs to get your eye in (and till you are remembering to toss tails or rings in the right direction!), and then do it properly for the next 50 (or 10%) lambs. 

If score 4 and 5 lambs are making up more than 10% of the mob, strongly consider choosing rams that will achieve your breeding objective, which should be a balance between reducing wrinkle and improving performance; this may mean changing studs or the type of ram you buy from your existing stud. In addition, cull your more wrinkly ewes. If less than 10%; consider not mulesing next time. 

If you are planning to stop mulesing, ensure you review your management, breeding, chemical and marketing strategies: don’t just stop mulesing. 

Doing this exercise each year will help you to assess how your breeding strategy is progressing. You may even record each score (1 to 5) separately (i.e. 5 containers of rings or 5 piles of tails or even someone recording with pen and paper) to give you better information.

Be aware that in good seasons lambs will be wrinklier than in seasons where ewe nutrition is not as good.