NZ Farmer - Explainer - why did 100,000 lambs die in the North Island?

Gerard Hutching explains this months high mortality rate in North Island lambs

Farmers in eastern and central North Island have lost 100,000 lambs in the first two weeks of the month.

What could farmers have done to lessen the toll?

Very little. From the beginning of the month for a week a cold southerly blast settled in over eastern and central areas of the lower North Island. It was accompanied by heavy rain, up to 275 millimetres in some locations.

Federated Farmers meat and wool chairman Miles Anderson speculates the rain may wash away the lambs' lanolin, which is a natural insulator.

Why didn't they rescue more?

Most of the deaths occurred on hill country farms. The steep terrain is a hazard for farmers, especially when it is wet. If they go into the paddocks they risk frightening the mothers who will then abandon their lambs. If they have been mis-mothered in this way, the young die of starvation. 

Most farmers scan their sheep so they know if they're carrying multiple and singles. They put the multiples in the more sheltered blocks because they are lighter and have fewer fat reserves than the singles which go in the more exposed places.

What else can they do?

Many farmers use woollen covers to protect the new born lambs. In the case of Patoka farmer Ben Crosse, he managed to save three-quarters of his at-risk lambs but he still lost about 750.

Often lambs and ewes are rescued and taken into sheds. But if they are left for a long time, they risk getting disorders such as mastitis and pneumonia.

What about better shelter?

No amount of shelter can protect a new born lamb against seven days of cold, driving rain. In fact unusually, some of the lambs which succumbed this month were three to four-week-olds.

One of the problems is that a large number of sheep tend to go to the shelter but then they churn it up, turn it into mud and the lambs have a lower chance of survival.

It's true though that in some areas such as Canterbury, shelter trees and hedges have disappeared to fit in irrigators.

What temperatures are too low for sheep?

To maintain its body temperature, a newborn lamb must produce as much heat as it is losing to the environment. The quicker a ewe licks off the lamb, the less vulnerable it will be to chilling.

The normal body temperature for lambs is 38.8 degrees, and lambs below 37.7 degrees are considered hypothermic. Once born, a lamb has to increase its internal heat production markedly - by an estimated 15 times - to maintain its body temperature. The colder the external air temperature, the greater the immediate stress on the lamb.

100,000 deaths sounds a lot

The figure has to be seen in the context of 19 million lambs and 3.3 million ewes being slaughtered a year. The most severe recent death toll was August 1992 when 1 million sheep died after a heavy snowfall hit Canterbury, reaching sea level.

Are lambs born too early or at the wrong time of the year?

There is a misconception that farmers have lambs too early because they are chasing after the United Kingdom Christmas market, when prices are higher. In fact, since the big swing into dairy in the last 20 years, there aren't as many lambs born early.

Lambing coincides with spring growth so the ewes will have enough milk to take the lambs through to weaning, and to make sure there's going to be enough feed for ewes and lambs.