Replacement rates in your sheep flock are determined by your ewe losses and your culling decisions. For every ewe lamb you choose to keep, that’s one less to sell. 

In this week's podcast, our guest, Associate Professor Anne Ridler, discusses the findings from her recent study on ewe wastage in New Zealand sheep farming. Anne’s research found that, on average, 28 to 30 per cent of ewes leave the flock annually in New Zealand. The study aimed to understand when and why ewes exit the flock and how to reduce that wastage. 

Let's break those numbers down … say you have 1,000 ewes at mating time:

• At scanning time, of those 1,000, 33 will leave the flock because they’re dry. 
• Before set stocking, another 18 ewes will go due to non-reproductive reasons such as low BCS and 17 will die in this time. So, of your original 1,000, you have 932 left by the start of lambing. 
• Lambing is the highest risk period, with two-thirds of your losses occurring during this period. The average is 3.7 per cent. So, that’s another 37 ewes leaving the flock up until mid-lactation/docking, leaving you with 895 ewes.
• If you decide to cull wet-dries at weaning, the average is 3.8 per cent, meaning another 38 ewes leave the flock, reducing your number to 874. In addition, another 33 ewes exit the flock between docking/tailing and breeding in year two, some of which will be wet-dries (on average, across all the farms), some will be culled for other reasons and some will die.
• Then, post-weaning, based on udder issues, age, teeth or other decisions, farmers choose to cull, on average, 15.4%. That leaves you with 708 ewes. So, 292 replacements need to enter the flock to get back to 1,000 ewes for breeding.

Whilst these numbers might seem a bit confronting, they give a great insight into how you can reduce the number of replacements you require.

With most losses occurring during lambing, Anne suggests this could be an area to focus on. Feeding ewes well during pregnancy (to avoid metabolic issues) is a big part of keeping your ewes alive. But there are other things you can do, such as paddock audits and cast beats. 

Mark and Anne also discuss other options such as keeping wet-dries and putting them to a terminal ram.

We would be interested to hear what you base your culling decisions on. Is it age? Do you give your wet-dries a second chance? Let us know.

The study from which this information was derived was funded by the Massey-Lincoln and Agricultural Trust and done in collaboration with Lincoln University.

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