Conduction of heat from sheep to ground

Gatenby, Ruth M.

doi:10.1016/0002-1571(77)90034-6

Cited by 27 publications

(16 citation statements)

References 13 publications

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“…Under calm conditions, recently shorn ewes also conserve body heat by spending more time standing than sitting (Hutchinson & McRae 1969;). Conductive heat loss from standing is negligible, whereas during sitting on grass it can be up to 30% of the animal' s minimum heat production (Gatenby 1977). Mixing shorn with unshorn ewes did not influence the proportion of shorn ewes lambing under shelter (Mottershead et al 1982).…”

Section: Behavioural Considerationsmentioning

confidence: 87%

The role of shelterbelts in protecting livestock: A review

Gregory

1995

New Zealand Journal of Agricultural Research

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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.

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Section: Behavioural Considerationsmentioning

confidence: 87%

The role of shelterbelts in protecting livestock: A review

Gregory

1995

New Zealand Journal of Agricultural Research

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“…Adult sheep use overhead cover to reduce radiative heat loss . They seek insulated resting areas (soft dead grass; ) and can lose a substantial amount of heat through conduction when resting on cold ground (Gatenby 1977).…”

Section: Effects Of Weather Conditions On Establishment and Maintenanmentioning

confidence: 99%

Shelter for lambing sheep in New Zealand: A review

Pollard

2006

New Zealand Journal of Agricultural Research

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Wind and wet coats create dangerous conditions for lambs, even at moderate temperatures. Lambs compromised by factors such as birth injury and small size are particularly at risk. Wet, cold, windy weather added 38-76% to mortality rates in Australian Merino and Corriedale lambs, and in New Zealand lamb breeds added 10-20% (more in snow conditions). Wind shelter removed 3-13% from single lamb mortality rates and 14-37% from twin lamb mortality rates in Australian Merino and Corriedale sheep, but was not effective in reducing losses of twins in cold or wet weather. In New Zealand, wind shelter (such as Pinus radiata tree shelter belts) has generally removed less than 10% from mortality rates. Effective shelter would protect lambs from wind, rain, radiative and conductive heat loss, as well as allowing lambs exposure to the sun. Shelter should be familiar and well dispersed to encourage ewes to isolate from other sheep at lambing. Scattered dense shelter within paddocks such as tussocks or forage grasses or shrubs is very likely to increase lamb survival and possibly growth. Lamb covers also provide effective shelter but are labourintensive to use. The benefits and management of effective shelter require research so that farmers can be provided with the incentive and means to reduce their considerable losses of neonatal lambs.

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“…In snow-covered habitats in winter, the insulation provided by the animal's winter pelage and the snow may minimize heat losses. For animals lying on cold, poorly insulated ground without snow or during early spring and summer conditions, conduction may aggravate cold stress and may be one of the more important ways of heat loss (Gatenby 1977). Standard operative environments would be colder than predicted herein if the heat lost by conduction (but conserved by lying) exceeded heat lost by convection (and expended during standing).…”

Section: Limitations Of Estimating Thermally Critical Environmentsmentioning

confidence: 81%