Shelterbelts for Livestock Productivity

Note Number: LC0138
Published: December 2002
Updated: October 2009

Shelterbelts have been used to protect stock from harsh weather conditions for hundreds of years.

Shelterbelts provide a range of benefits for the protection of stock and improved productivity levels.

Introduction

The ability of shelterbelts to reduce stock losses from extreme weather conditions is well known. Shelterbelts are often established to protect newly shorn sheep, lambs and stock in poor condition from what can be highly lethal conditions.

Shelterbelts also provide other benefits to livestock enterprises such as improved productivity from pastures, protection from heat stress, increased ram fertility, and reduced feeding requirements of stock.

Reducing stock losses

Through reducing the level of exposure of stock and pastures to harsh conditions, shelterbelts can improve the productivity levels of a livestock enterprise. One of the most important roles a shelterbelt can play is the prevention of the death of livestock due to exposure during harsh weather conditions.

Shelterbelts do this by providing shelter and reducing the effects of 'wind chill'. Wind chill is the combined effect of low temperatures and wind. The wind increases the loss of body heat from the livestock. During wet conditions the impacts of wind chill combined with wet stock can be lethal.

A reduction in mortality of newly born lambs is one of the most well recognised roles of shelterbelts. Lamb losses have been estimated to be an average of around 15% in southern Australia. Trials conducted in southeast Australia indicate that losses of newborn lambs can be reduced by 50%.

Shelterbelts provide similar benefits for newly shorn sheep. Sheep are very susceptible to harsh conditions during the first two weeks following shearing. The condition of the stock at this time is also a contributing factor to losses. Records of losses of off-shear sheep show a total of 250,000 sheep were lost over 4 days of adverse weather conditions. The provision of shelter can prevent or reduce these losses.

Many examples of reduced stock losses on properties with shelter both locally and inter-state demonstrates the benefits of protecting stock during harsh conditions.

Enhanced productivity

Providing shelter for stock can increase productivity in a number of ways. Shelterbelts can improve pastoral productivity, improve the condition of stock and increase feeding efficiency. Studies have shown that sheltered pastures and crops can be more productive. By reducing the speed of drying winds, pastures have more moisture available to them and grow at faster rates.

Studies conducted in the U.S.A. on pasture and hay yields over a 14-year period have shown that yields are higher in pastures that are sheltered. Similar studies in Australia have also found an increase in plant biomass associated with shelterbelts.

The provision of shelter also has some more direct benefits for stock. Stock in a sheltered paddock are less exposed to harsh climatic conditions as the shelterbelt creates a microclimate that protects stock from weather condition extremes.

The provision of shelter can reduce the effects of hot, cold and windy conditions. The energy stock would normally expend on maintaining their body temperature can then be utilised for increased wool, meat and milk production.

Higher rates of pasture productivity and lower amounts of energy expended on body temperature maintenance by stock can lead to higher levels of condition, higher birthing rates, higher stocking rates and/or lower requirements for supplementary feeding.

The provision of shade can also increase ram fertility over the warmer months while research has found that cattle within sheltered paddocks have an average 2% higher calving rate and that the amount of feed required to maintain body temperature is substantially reduced.

Shelterbelt design for livestock

A number of design aspects need to be considered for the establishment of shelterbelts for stock protection. The length, height and density of a break determine the area of protection it provides. Generally a multi-rowed break with a density of 60-80% will protect an area downwind of fifteen times the height of the windbreak.

The area required to be protected and the prevailing wind directions need to be determined.Taller belts with medium levels of density will protect a larger area than belts that have less height or very high densities. The profile of the belt will also determine the area it protects. For maximum area protection a belt should contain taller species on the windward side and shorter species such as shrubs on the leeward side.

Belts consisting of only one or two rows can achieve higher density levels by spacing plants closer together. However, narrow belts are more susceptible to gaps due to the loss of individual plants and are less likely to have even density levels.

The location of belts is critical for maximum efficiency and to achieve the objectives of the belt. The location of belts is best determined through a Whole Farm Planning Process. The aim of Whole farm planning is to integrate productive aspects of farm management with conservation. Whole Farm Planning involves the use of an aerial photograph to develop a farm plan that takes into consideration the natural characteristics of the farm and a range of other factors to improve farm management.

The prevailing wind direction may not necessarily be the most important wind to protect stock from. Often the winds that cause the most damage and stock losses come from directions other than the prevailing wind direction.

A good shelterbelt will have even density down to the ground for stock protection. If the density of the belts is less at the ground level then wind will channel through the less dense part of a belt at an accelerated rate. This accelerated wind can be lethal to stock which graze at the ground level.

It is important to be able to easily move stock to sheltered areas during harsh conditions and therefore to place shelter in the down-wind corners of a paddock. Sheep are often driven by wind making it difficult to move them in a direction opposite to the wind direction.

It is not only sheep that are susceptible to harsh conditions. Calves, goats and pigs are also susceptible to weather extremes.

Stock havens

Stock havens are areas of land that are revegetated to provide high quality shelter for stock to be contained within during extreme weather conditions. They are often built in a boomerang or kidney shape to create a sheltered pocket for stock. Stock havens are ideal for large paddocks and lambing ewes. Stock havens provide a higher degree of wind protection over the area it shelters. Well-vegetated laneways can act as stock havens during poor weather conditions.

Stock havens provide shelter for stock grazing in the paddock but can also be used during extreme weather conditions to provide a higher level of protection by holding stock within the haven itself.

Conclusion

A well designed and located shelterbelt can deliver a range of benefits for a livestock enterprise over a very long period of time. Shelterbelts can improve productivity by increasing birthing rates, protecting newly born lambs and newly shorn sheep, reducing energy requirements of stock and improving pastoral productivity.

As well as enhancing productivity, shelterbelts can improve the sustainability of a farm through reducing erosion and the impact of salinity. Shelterbelts can improve the aesthetic and capital value of a property as well as providing an improved working environment.

References:

Burke, S. (1998) Windbreaks. Inkata Press, Sydney

Bird, P.R. (1998) "Tree windbreaks and shelter benefits to pastures in temperate grazing systems". Agroforestry Systems 41: 35-54. (and other papers in that volume)

Bird, P.R., Bicknell, D., Bulman, P.A., Burke, S.J.A., Leys, J.F., Parker, J.N., van der Sommen, F.J. and Voller, P. (1992). "The role of shelter in Australia for protecting soils, plants and livestock". Agroforestry Systems18: 59-86.