Animal Science

Opinion: Lamb survival in Spring storms

1 October 2018
Opinion: Lamb survival in Spring storms | NZ Farm Research

by Science Impact Leader, Dr. Sue McCoard

Severe lamb losses in recent weeks, as a result of Spring storms, have sparked a fresh debate about what more our farming sector can – or should – be doing to prevent deaths on such a scale.

One report estimated 100,000 lambs were lost in the eastern and central North Island alone, while the deep south was also hit by big dumpings of snow – the often-seen nasty sting in the tail of winter.

It moved one social media commentator on farming to argue these kinds of losses are preventable, and to call for a change in “our expectations around lamb survival” and “our lambing culture”.

Losses like these are of course devastating for farmers, and the concern from the general public is also understandable. We have to acknowledge lambing at times where there is a risk of storms does come with inherent risks.

In reality, there is only so much that can be done when the worst storms hit, and the focus does need to be on how to reduce losses as much as possible.

We now have a good understanding through the research about the importance of shelter and how best to prepare animals for these type of weather events. However when these events do strike, methods that are available are not always practical or easy to put in place, or effective as we would like.

The wind-chill in these storms is certainly the biggest killer for newborn and young lambs, and in that respect, shelter makes the greatest difference in their survival. There is evidence ewes will use shelter if available, though there may be a conflict with their instinct to be isolated when lambing.

Shelter can take many forms, including physical shelters like sheds, through to wind-breaks or long grass, rushes, or humps and hollows in the land.

The risk of course with shelter, and this is where farmers may have had bad experiences affecting their approaches, is that where sheep congregate there is a risk of smothering of the lambs, mis-mothering and disease due to poor hygiene.

Moving stock in large numbers in the middle of lambing can also cause more problems than it solves due to mis-mothering etc; meaning shelter has to always be within easy reach during lambing – posing a further challenge.

Our research tells us that what farmers do with their ewes pre-birth can make a real difference to the survival of the lambs when the cold weather strikes. Ewes that are well-fed and in good condition generally will give birth to good sized, strong, viable lambs that have a greater chance of survival in severe weather events (given both the ewe and the lamb are more resilient).

Lambs most at risk of dying in the bad weather are typically those with lower birth weight; poor body reserves (brown fat and muscle); lambs that are under-fed (often from ewes not milking well); those born to under-weight ewes or ewes with poor mothering ability that abandon their offspring at birth; those who went through a difficult birth that reduces their vigour; and those unfortunate enough to be buried in snow or washed away in floodwaters, or born or stuck in puddles.

Our experience is that farmers are aware of the risks and generally provide the best environment they can for their stock. Many farmers also save up feed in spare paddocks, or supplementary feed, to provide to ewes when the weather turns nasty.
We are also seeing some farmers split flock lambing now, to reduce the risk of having all of their ewes lambing at the same time.

Our role as researchers is to continue to provide the best evidence and guidance to farmers as they face these difficult issues around lamb survival.

More research is certainly needed to identify ways to improve survival rates – especially where ewes have two or more lambs, presenting a higher risk for the lambs’ survival in poor weather. That is something we are firmly focused on.

With more research, we can better work with farmers towards a long-term vision of where the sector and the public wants to be on these issues.