Overstory #85 - Animal Shelter
Windbreaks are groups of trees or shrubs in any arrangement that will afford protection from wind to crops and/or animals. Previous editions of The Overstory (#32 and #73) showed how windbreaks can be used to protect crops from the damaging effects of wind. In this edition, special guest author Steven Burke shows how windbreaks also are very valuable for protecting animals from the elements.
Extremes in climatic conditions can have enormous effects on the productivity of farm animals. Numerous studies indicate that the provision of shelter improves livestock performance through moderation of some of these effects.
Windbreaks can improve pasture production, which in turn provides benefits to livestock. More available feed means that animals will be heavier and healthier, or that higher stocking rates can be maintained. In addition to providing more feed, windbreaks can offer other important benefits to animals including increasing weight gain and health, and moderating the harmful and potentially lethal effects of wind, rain, sun, and cold.
Healthier and more productive animals
Animals protected by windbreaks can be healthier and more productive. Productivity of farm animals is optimal for a comfort zone of a relatively narrow temperature range. Animals experiencing excessively hot or cold conditions require more energy to maintain basic metabolism and thus have less energy available to increase body weight or to produce meat, milk or wool. In other words, more feed is required to counter environmental stresses. Under adverse conditions, livestock performance is inefficient relative to the quantity of feed consumed.
Experiments with sheep and cattle have shown that strong wind and rain double the energy requirement of animals for maintenance. One Australian study from the New England Tablelands in New South Wales showed that cold stress can depress sheep liveweight gain by 6 kg, and can depress wool growth by 25% (Lynch and Donnelly 1980). A study in Montana in the USA showed that beef cattle protected by windbreaks were on average 16 kg heavier than those in unsheltered feedlots. It is well known that dairy production is improved by providing sheltered conditions. In southern Victoria it has been calculated that the provision of shelter can increase milk production by 30%. Ten per cent of this is due to greater efficiency of conversion of feed, and 20% due to the greater amount of feed available (Fitzpatrick 1994).
Grazing behaviour, and consequently feed intake, can also be affected. This may be partially compensated for by increased grazing when the conditions moderate. Animals under adverse environmental conditions generally graze less, and sometimes not at all.
Example: Intensive Shelter for Dairy Production
Simon Park sees a number of benefits flowing from the establishment of an intensive shelter system from his 120 ha dairy property near Wonthaggi, Victoria Australia. Simon has developed a long-term whole farm plan which features paddock subdivision and the planting of a regular series of windbreaks on the paddock boundaries. The windbreaks are generally parallel and spaced from 50-100 m apart, producing a very intensive shelter system.
Windbreaks are being established by a combination of direct seeding and planting of seedlings. Simon is convinced of the increased milk yields that can result from sheltered grazing conditions for his herd. The farm is also near the coast and very windswept, so increased pasture growth can be expected from the provision of intensive shelter.
Priority for shelter
Areas where animals are confined, such as stockyards and feedlots, should be given high priority for protection by high quality windbreaks. Sheltering these areas will reduce feed requirements, improve the weight and condition of stock, and result in improved animal health.
Although cattle are much more hardy than sheep, calves can still be susceptible to exposure, especially when newborn. On average, in Kansas in the USA, a 2% increase in calf survival is gained from the provision of windbreaks. Pigs and goats are extremely susceptible to death from exposure, even more so than sheep. This is because they do not have skin covering with the same thermal properties as greasy sheep wool. Shelter should be a high priority for these animals.
In livestock areas with large paddocks, consideration should be given to the establishment of carefully located within-paddock shelter. Observe the movement of animals in bad weather. Sheep in particular will end up in the downwind corner. Special arc-shaped windbreaks can be planted to protect these critical areas.
Special livestock havens also have considerable merit for exposed areas with no naturally sheltered areas. A livestock haven is essentially an area enclosed by windbreaks providing a very high degree of wind protection. Farms with many dispersed trees can still incur high stock losses in severe weather. The key is to have areas of high quality shelter available and, importantly, people on hand to move stock into these protected areas at critical times. Woodlots and agroforests can also be ideal areas to locate vulnerable stock in severe conditions.
Windbreaks are also extremely useful when located along passageways, as animals can take shelter in lanes during extreme conditions. For this reason, passageways protected by windbreaks can provide a very effective backbone for a shelter network.
Example: Passageway Shelter a Safe Haven
Neil and Sue Lawrence have established over the years a network of passageways across their 1,000 ha Balmoral property in western Victoria. The passageways are a tremendous labour saver when moving stock around the property. In some areas, around the house and shearing shed, red gums (Eucalyptus camaldulensis) have been established by direct seeding to provide shelter to the passageways and surrounding areas.
A cold southerly snap hit in December 1987 during shearing when 1,600 off-shears sheep were held in an exposed paddock near the Lawrence's house. During the wild night, they moved the sheep into a sheltered passageway. hey lost 23 sheep in the 200 m before reaching shelter, but all those that made it survived. "In the passageways it was as though a switch had been turned off a big fan. The sheep stopped dying and some even started to graze."
While the Lawrence's flock escaped almost unscathed, one neighbour lost 600 off-shears sheep and the district total was 30,000. Neil reckons that the $200 or so that it cost him to direct seed those trees was the best investment he ever made.
Shelter from sun
Shelter trees can also provide substantial additional benefits due to the provision of shade. In warmer regions, provision of shade should also be considered to reduce stock losses (particularly for calves and lambs) from heat stress. Where these benefits are likely to be substantial, shade plantings within paddocks should be considered in addition to windbreaks.
Shade can also make a valuable contribution to animal production, particularly in hot areas, such as the semi-arid and tropical north of Australia, but seasonal benefits can also be obtained in temperate regions.
Excessive heat depresses the condition of cattle by reducing feed intake. Heat stressed cows produced fewer calves and the calves produced have a lower birth weight. Calves frequently die of heat stress, particularly in tropical northern Australia. Heat stress can also markedly affect dairy production. One Queensland study (Davison et al 1988) showed that the provision of shade increased milk production for each cow by 2 kg per day combined with an improvement in milk composition. European cattle breeds benefit more from provision of shade than tropical breeds.
For sheep, excessive heat is detrimental to ram fertility, and in ewes can reduce ovulation rate and conception. Heat stress in sheep can also lead to death, particularly for lambs. Ewes will assist their lambs to seek shade if this is available (Bird et al 1984).
Protection from cold and wet conditions
Where livestock graze in the open year round, and they may consequently become susceptible to harsh climatic conditions from time to time. Of the three factors which create exposure problems in livestock (cold, wet and wind), wind is the most practical to moderate through the provision of shelter.
The greatest reductions in mortality from exposure are produced by windbreaks designed to provide significant wind reductions when conditions of extreme exposure arise. Areas of high quality shelter created by dense windbreaks are required to achieve the maximum benefits. Alternatively, stock can be confined in paddocks with natural shelter due to topography or dispersed shelter across the paddock such as tussock grasses or shrubs.
Cold, wet and windy conditions frequently combine to produce conditions lethal to animals in the field. Wind chill is the effect of increased cooling experienced because of the combined effect of wind and low temperature. This occurs because wind increases the loss of body heat from the surface of an animal. This situation becomes even worse when the animal is wet, and heat losses due to evaporative cooling also occur. Animals in the open under these conditions can be extremely vulnerable.
For example, the most widely recognised benefit of shelter to livestock in southern Australia is the prevention of the death of newborn lambs from exposure in wet, cold, windy weather. Most lamb losses occur within three days of birth. Lambing percentages can be very low in many regions in Australia because of this problem. It has been estimated that in southern Australia, on average, as many as 15% of newborn lambs die from exposure. Several Australian studies have shown that lamb mortality in cold, wet weather can be at least halved by the provision of adequate shelter. Lamb losses can be commonly reduced from 20% to 10% by the provision of adequate shelter and stock management.
A chill index model has been developed (Donnelly 1984) which relates temperature, rainfall and wind speed to lamb mortality. This shows that by reducing wind speed from 10 m/s to 2.5 m/s through the provision of shelter, lamb mortality is at least halved. Ewes do not always seek shelter when lambing, and natural sheep camping and lambing areas are often on exposed high ridges. Unshorn ewes are less likely to seek shelter to lamb than shorn ewes. To minimise lambing losses, either dispersed shelter must be available across the paddock, the natural lambing sites must be sheltered, or the ewes must be confined to a "lambing haven," a confined area of high quality shelter. Good management is important to ensure lambing ewes are in the right place at the right time. Set stocked lambing paddocks need to contain enough feed to last the lambing period, often 6-10 weeks.
In the case of sheep, the benefits of shelter have been shown to include increased feed availability, reduced lambing losses, reduced off-shears losses, and increased efficiency of conversion of feed to meat and wool. In southern Victoria it has been estimated that these factors can combine to produce an overall increase in sheep productivity of 29% (Fitzpatrick 1994).
If high quality shelter is available for susceptible stock, it is important to plan ahead to ensure the ability to move them quickly to these areas in bad weather. It can be worth changing the location of fences to encourage stock to move to shelter in bad conditions. The location of shelter is crucial, it is often best to locate areas of maximum shelter in the downwind corners of paddocks or on high ground because sheep are often driven by high winds and it can be very difficult to move sheep into a gale.
The provision of adequate shelter can prevent dramatic stock losses under extremely adverse conditions. It can also provide small regular returns due to improved animal productivity. Shelter therefore produces a combination of benefits to livestock.
Bird, P.R., J.J. Lynch, and J.M. Obst. 1984. Effect of shelter on plant and animal production. In: Proceedings of Australia Society for Animal Production 15: 270-3.
Davison, T.M., B.A. Silver, A.T. Lisle, and W.N. Orr. 1988. The influence of shade on milk production of Holstein-Freisian cows in a tropical upland environment. In: Australian Journal of Experimental Agriculture 28:149-54.
Donnelly, J.B. 1984. The productivity of breeding ewes grazing on lucerne or grass and clover pastures on the tablelands of southern Australia; III: Lamb mortality and weaning percentage. In: Australian Journal of Agricultural Research 35:709-12.
Fitzpatrick, D. 1994. Money Trees on Your Property: profit gained through trees and how to grow them. Inkata Press, Sydney.
Lynch, J.J. and J.B. Donnelly. 1980. Changes in pasture and animal production resulting from the use of windbreaks. In: Aust Journal of Agricultural Research 31:967-79.
This article was adapted with the kind permission of the author and publisher from:
Burke, S. 1998. Windbreaks. Butterworth-Heinemann, Woburn, Massachusetts, USA.
This comprehensive and well-illustrated book covers the siting, design, species selection, establishment, and maintenance of multipurpose windbreaks.
About the Author
After graduating with an honors degree in Forest Science from the University of Melbourne, Steven Burke worked for seven years providing forestry extension services to landholders in Victoria, Australia. Following his strong interest in windbreaks and other agroforestry systems, he undertook landmark graduate research into crop responses to windbreaks in South-Eastern Australia which resulted in a Masters Degree in Agricultural Science. He has also managed statewide programs in community forestry and community-based revegetation whilst working for the Non-Government Organisation Greening Australia, and managed pest plant and animal management programs for the Victorian Department of Natural Resources and Environment. He is currently working on weed and vegetation management projects for King County in Washington State, USA.