The role of shelterbelts in protecting livestock: A review

Abstract

Planting a shelterbelt is the only option open to some New Zealand livestock farmers for reducing the adverse effects of wind. Wind reduces pasture productivity by mechanically agitating the leaves and this results in inhibition of plant cell expansion. It causes greater evaporation and physical damage to the plants, which also reduce pasture yield. At any given temperature, wind raises the lower critical temperature for an animal, and this is potentially wasteful in terms of energy utilisation, and it increases the risk of hypothermia and mortality in particularly sensitive stock such as newborn lambs and recently shorn ewes. Ewes that are shorn pre-lambing seek protection from the wind and there is a greater likelihood of them lambing within shelter if it is available. The tendency to lamb in isolation away from shelter depends on breed and weather conditions. For most purposes, the best shelterbelt is one which has between 40 and 60% porosity that is distributed evenly throughout its length and height and protects the maximum area of pasture from the wind. Under cold conditions shelter has been shown to improve pasture yield, and growth rate, ovulation rate, and wool growth rate in cattle and sheep, and to reduce lamb mortality and abortions that are induced by hypothermia. Providing shelter from the sun during hot conditions has been shown to improve milk yield, milkfat yield, freedom from mastitis, and conception rates in dairy cattle, and growth rate in fattening cattle. The welfare benefits from A95037 shelterbelts and shadebelts are implicit in their greater use during cold-windy and hot-sunny conditions and they relate to the thermal comfort of animals. The purpose of snow shelterbelts is to filter the wind and trap snow without forming snowdrifts in which stock are likely to be trapped. Their effectiveness depends largely on the amount of snow falling relative to the size and porosity of the shelterbelt. Trees-on-pasture systems provide protection from wind and raise the minimum grass temperature, but because of the competition introduced with the trees they are usually less productive in terms of livestock yield than pasture alone. There are a number of disadvantages in growing shelterbelts but many of them can be controlled with appropriate management procedures.

Shelter for lambing sheep in New Zealand: A review

“…Usually it is recommended that wind-permeable barriers such as windbreak material or trees are used for stock shelter, because solid barriers create turbulence on the leeward side (Gregory 1995). However, ewes and lambs prefer barriers with low wind permeability (Winfield et al 1969;Lynch & Alexander 1977;Alexander et al 1979;.…”

“…In both studies a higher incidence of internal parasitism was observed in the sheltered groups. Other health problems may be associated with shelter, such as footrot, Clostridia infections and facial eczema (Gregory 1995).…”

Quantifying the effect of thermal environment on production traits in three breeds of dairy cattle in New Zealand

“…The lower critical temperature for a dairy cow in peak lactation is around -30°c in dry, still conditions (Blaxter 1958;young 1981;Gregory 1995). These lower critical temperatures may be more relevant for Northern Hemisphere environments where housing is common, thereby limiting exposure to wind or rain.…”

Productivity and nutritive value of brachiaria forage intercropping with eucalyptus in a silvopastoral system in the Brazilian Cerrado biome

“…The higher forage production in May and November is due to greater plant development in these periods, which are periods close to the rainy season, compared to forage production in the middle of the drought period of July. This also explains the smaller forage height in July and taller height in November (Table 5).Trees contribute to the conservation of soil cooling and moisture, by protecting the area from direct sun light and winds that sweep the humid air (Gregory, 1995). Thus, the SSP increases absorption of nutrients by forage, resulting in a higher content of biomass and improving the bromatological quality of pastures.…”