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Improving Lambing Percentages With Strategic ShelterbeltsLamb mortality from exposure to bad weather can be reduced by up to 50% when paddocks incorporate shelter. By Department of Primary Industries - 6th July 2006 - Back to News Windspeed, low temperature and rain combine to create a "chill factor" and this causes lambs to lose heat more rapidly than the body can cope with. Strategically located plantations can dramatically reduce the chill factor, assisting in increasing lamb survival during bad weather, particularly during the first three days after birth.
Ewe behaviour
Ewes close to lambing have a tendency to move upslope to higher ground. Shelterbelts must be strategically located to exploit this behaviour. Shelter located only along paddock boundaries can be ineffective if strong winds drive the ewes into an exposed corner. Studies have shown that shorn ewes are more likely to seek out shelter for lambing, whereas unshorn ewes do not. This puts recently born lambs at high risk of hypothermia or pneumonia in bad weather.
Paddock planning
Shelterbelts
Boomerang-shaped plantations using a combination of trees and shrubs across a slope will give protection from several directions. A total length of 200m x 20m or wider will give useful shelter to lambing ewes and young lambs. Fenced boomerang-shaped mid-paddock plantations used in conjunction with boundary plantations are most effective when lambing paddocks are relatively small. Circular plantations without stays, and therefore cheaper to fence, can also be effective. Relatively small, well-sheltered paddocks break up the wind, preventing extreme windchill from occurring. As the amount of open space increases in a paddock, so too does the windspeed and chill factor.
Another design uses the "tree haven" where blocks of 1-2 ha are planted to trees, which are spaced wide enough to allow vehicle access for feeding sheep in bad weather. Shrubs are planted on fenced western, southern and northern perimeters. The shrubs act to "lift" the wind over the tree haven rather than the wind tunnelling through at sheep height with increased speed. Ewes or freshly shorn sheep are given access to the tree block when bad weather is predicted. If the block is not located where sheep are likely to use it passively, then they are driven into the tree haven and remain there until the weather improves.
One gateway into a tree haven paddock must be located to allow quick and easy movement of livestock, possibly off a laneway. This can be important for quickly moving recently shorn sheep prior to when gales or severe weather warnings are issued. A second gateway might be located from the tree haven into a larger paddock to allow livestock to access the shelter as part of the larger paddock (ie during cold or very hot weather).
For shelterbelts to be effective against wind chill, sufficient shrubs must be included to provide low shelter and prevent wind tunnelling through the belt. The windbreak must be fenced to exclude livestock to preserve this benefit. The tree haven design can be created using farm forestry species that are high pruned for clearwood timber suitable for furniture and flooring.
Spring planting 2006
Now is the time to consider which paddocks would make ideal lambing paddocks or have a tree haven incorporated into larger paddocks. Consider the existing shelter in paddocks closest to the house. These paddocks will be the quickest to check in bad weather particularly for use as lambing paddocks when valuable ewes may be in lambing difficulty. Shelter combinations using direct-seeding and tubestock can be used to create very effective havens for stock during bad weather.
Source: http://gippsland.com/ Published by: news@gippsland.com
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