Lamb marking percentage is one of the main factors influencing the profitability of a sheep enterprise.

According to Trees on Farms advisory officer with NSW Department of Primary Industries, Dhyan Blore, "research on the tablelands shows that lamb survival can be increased by 10 to 20 per cent where good shelter exists".

"It is important to understand sheep behaviour in designing shelter, as sheep generally camp on high dry positions in the paddock.

"These positions are often very exposed and lamb mortality can be high as a result," Ms Blore said.

Lambing ewes can be steered into sheltered camp sites via their natural behaviour patterns, if fences are realigned to make use of paddock topography.

In flatter country, windbreaks are very useful in providing shelter.

A well designed windbreak can reduce wind speed between 25pc and 75pc, for a distance of several hundred metres out into the paddock.
Newborn lambs are very susceptible to cold stress.

Rain in combination with wind dramatically reduces the insulating value of the lambs coat.

Ms Blore says that in cold weather even a modest wind can dramatically reduce the temperature experienced by lambs.

"For example if the still air temperature is four degrees with even a modest wind of 20 kilometres per hour, the effective temperature experienced by an animal is minus four," she said.

Effective windbreaks can reduce wind speeds to less than eight kilometres an hour (equal to a slight breeze), significantly reducing wind chill deaths in lambs.

For lambs it is very important to have good low shelter to reduce wind speeds close to the ground.

"In planning windbreaks, it is best to orientate plantings at right angles to worst prevailing winds, use at least three rows to prevent gaps and choose trees and shrubs with foliage low to the ground," Ms Blore said.

Contact Dhyan Blore, Orange, (02) 6391 3905, dhyan.blore@dpi.nsw.gov.au