A focus to much of my recent work with sheep and beef farmers has been to review last season’s productive performance, identify key opportunities for improved productivity and then to develop strategies and put in place plans to deliver on these objectives over the upcoming season.

In the sheep production system two frequently identified opportunities are: 1) improve lamb survival from scanning to weaning, and 2) improve lamb pre-weaning growth rates.

In my experience, high lamb wastage is the most underestimated source of lost production potential in the New Zealand sheep production system. It is often accepted as a reality of pastoral farming and too little attention is focused on changing this variable.

Based on current NZ statistics, total lamb wastage between scanning and weaning equates to a missing 9kg of lamb weaned for each cross-bred ewe mated.

First, make sure you are calculating lamb wastage correctly. An example farm has 2000 ewes scanning at 160%. The farm weans 2600 lambs. What is the scanning to weaning wastage rate?

  • The potential number of lambs is 2000 ewes x 160% = 3200 potential lambs
  • The difference between actual and potential is 3200 – 2600 = 600 lambs
  • The lamb wastage rate (%) = 600 lost lambs ÷ 3200 potential = 0.1875 = 18.75%

Where should I start looking for opportunities to improve?

Paddock/block tailing tallies – Across each block for the last couple of years calculate the lamb wastage rate to identify wastage hot-spots. Factors that may drive high wastage at a paddock/block level may include:

  • Aspect – south facing blocks will be more exposed to severe cold-weather events.
  • Slope – wastage rates in multiple lambs increase as slope increases.
  • Lack of shelter – flat, cultivated paddocks with poor shelter can experience high wastage despite good quality feed.

Blocks with consistently high wastage rates may be better suited for lambing singles, late ewes, or be set aside to rotate ewes and lambs into once lambs are up and away.

Shearing is hugely stressful – Shearing in the second half of pregnancy is, in my opinion, inviting lamb losses. Avoid winter or pre-lamb shearing.

Pre-lamb treatments – modern practices are hugely stressful. I regularly visit farms who muster nearly the whole farm to funnel every ewe through a conveyor two weeks out from lambing. We know that feed restriction of just a couple of hours can trigger metabolic diseases (sleepy sickness/milk fever/grass staggers) in ewes at this stage of pregnancy. Despite this, we will happily muster thousands of ewes into holding paddocks, spend a day or two working them through wet, muddy yards, inject and drench them across a conveyor, and then drive them back across the farm to suddenly change their diet for lambing. We need to do better. Where do I see the answer?

  • Complete pre-lamb treatments early and take it slow. Vaccinate ewes at least a month before lambing in smaller groups. Utilise satellite yards, spread out your workload. Your staff and your stock will thank you for it.
  • I discuss the label claims of vaccines with clients and discuss the risk/benefit of vaccination earlier than the label. There is a trade off in protection periods for the lambs, particularly against pulpy kidney, but on most farms this can be offset by vaccinating lambs at tailing if the risk of pulpy kidney in pre-weaned lambs is high. I encourage you to dive into this topic with your veterinarian.
  • Ewes re-enter their winter feeding program and then are set-stocked closer to lambing without the additional stress of large musters, a day in the yards, mob pressure, dogs, and a needle.

“Based on current NZ statistics, total lamb wastage between scanning and weaning equates to a missing 9kg of lamb weaned for each cross-bred ewe mated.”

Udder disease – ewes with bad udders lose their lambs. Recent NZ work has highlighted that on average, ewes with an udder lump, a hard udder, or a teat defect will lose 30-40% of their lambs, compared with 12% wastage in ewes with normal udders. ID and cull these ewes before you tup them, they are doing you no favours at all. For further information, there is research into reducing ewe wastage published by Massey University’s Professor Paul Kenyon and Lecturer in Pastoral Livestock Health Kate Griffiths.

Late pregnancy body condition loss – you need to do a winter feed budget now while you still have options to influence feed supply. You still have time to sow Italian ryegrass, apply nitrogen, or buy supplements.

You also have time to sell some older ewes, exit those trade cattle, or graze some hoggets out if you can’t get the winter budget to balance. A twin bearing ewe in late pregnancy needs 2 x maintenance to keep her body condition stable. Ewes dropping condition in late pregnancy is extremely common and it results in the birth of smaller lambs with reduced fat reserves. These lambs take longer to suckle, have less energy available to stay warm, and they die in larger numbers. The feed budget you do now is worth every minute you put into it.

Identify mobs with high ewe wastage – a dead ewe takes all her lambs with her and this can account for significant lamb wastage in some groups of ewes. Triplet bearing ewes and old ewes can experience very high ewe wastage. The management of these problems starts in the autumn by feeding to maintain these ewes at BCS 3-3.5 from the point of tupping through to lambing. Avoid gaining excessive body condition in autumn and avoid body condition loss in winter. I avoid very lush, super-high quality feed and prefer these ewes lamb on well sheltered, permanent pasture.

Iodine – if pregnant ewes are fed brassica, always supplement this with iodine. In some cases, ewe on pasture will still be iodine deficient. Lamb autopsies in the spring will help confirm the diagnosis. Discuss the need for supplementation with your vet.

Lamb autopsies – I do promote the value of lamb autopsies. For abortion related investigations, an un-scavenged, freshly aborted foetus and placental membranes will give your veterinarian the best chance of reaching a diagnosis.

For lamb losses around the point of lambing, I encourage farms that I work with to freeze groups of dead lambs. These can be defrosted prior to my visit and I can work through 15-20 lambs at once. This exercise can help narrow down likely contributing causes and focus attention for the next season.

While spring is half a year away, many of the strategies to minimise lamb wastage have steps to implement now. I would encourage you to go through the exercise of working out how much lost production there is in your lamb wastage figures. Challenge yourself to do better.

  • Ben Allott is a North Canterbury veterinarian.