Relation of Environmental Temperature During Gestation to Birth Weight and Mortality of Lambs

Shelton, Maurice

doi:10.2527/jas1964.232360x

Cited by 38 publications

(23 citation statements)

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“…Reduced birth weights have been documented for lambs exposed to high environment temperatures during gestation (Yeates, 1958;Shelton, 1964b). Reduced birth weights have been documented for lambs exposed to high environment temperatures during gestation (Yeates, 1958;Shelton, 1964b).…”

Section: Discussionmentioning

confidence: 99%

Genetic parameters for lamb birth weight in spring and autumn lambing

Al-Shorepy

Notter

1998

Anim. Sci.

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Genetic parameters for birth weight were estimated for two sets of spring-born and one set of autumn-born lambs of the same breed composition and genetic origin using a model that included random additive, additive maternal, permanent environmental maternal, litter and residual effects. Litter effects were significant for all data sets, indicating that within-year effects of common environment and (or) non-additive genotype were important for birth weight and should be included in genetic evaluation programmes. Estimates of variance components for autumn-born lambs differed significantly from those obtained from spring-born lambs or from the combined data. In contrast, estimates obtained for the two sets of spring-born lambs did not differ from those obtained when data on all spring-born lambs were pooled. The estimate of h 2 for birth weight in spring-born lambs was over twice as large as that obtained for autumn-born lambs (0-26 v. 0-22). In contrast, the across-year repeatability of ewe effects was much larger in autumn lambs (0-41 v. 0-26) as was the full-sib littermate correlation (0-73 v. 0-49). Mean birth weights were also 0-4 to 0-6 kg less in autumn lambs. These results suggest that negative effects on birth weight that have been reported for lambs gestated during summer in equatorial and subtropical regions are also manifested (albeit at reduced levels) in less extreme climates (in this case, 37°, 15' N latitude and 654 m elevation) and that maternal variation exists in the ability of the ewe to maintain adequate lamb birth weights in autumn lambing systems.

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Section: Discussionmentioning

confidence: 99%

Genetic parameters for lamb birth weight in spring and autumn lambing

Al-Shorepy

Notter

1998

Anim. Sci.

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“…Pregnancy during long periods of hot weather may result in lambs of reduced live weight and viability (Shelton, 1964). The WM ewes in the present experiment were subjected to much shorter periods of similarly high temperatures.…”

Section: Discussionmentioning

confidence: 99%

“…This effect was thought to be due to the removal of heat stress from the ewe, which is known to cause reduced birth weights and increased lamb mortality (Shelton, 1964;Alexander and Williams, 1971). Austin and Young (1977) postulated that maternal glucose elevation after shearing may permit increased foetal growth.…”

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confidence: 98%

The effect of environmental temperature during pregnancy on thermoregulation in the newborn lamb

Stott

Slee

1985

Anim. Sci.

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Twenty-four pregnant Scottish Blackface ewes were divided into three temperature-treatment groups 14 days before expected lambing: closely shorn and kept at 6°C (cold treatment, CD); in full fleece at 26°C (warm treatment, WM); and in full fleece at 6°C (controls, CL). Food allocation and intakes were similar for each group. Their lambs were tested for cold-induced summit metabolic rate capability (SMR) on the day of birth at a mean age of 12 h using water immersion to provide cooling. On the following day, the calorigenic response to subcutaneous injections of noradrenaline (NA) was measured to assess non-shivering thermogenesis capability. The ewes were blood-sampled during pregnancy and the lambs before and after the SMR test.In the ewes, .blood glucose and free fatty acid levels were higher during cold treatment, but not significantly so. Blood glucose was lower in lambs from CD ewes (CD lambs) before SMR tests; other differences were not significant.During the cold test, SMR was highest in CD lambs, but not significantly so. Rectal temperature declined least during test in the CD lambs (P < 0-05).The peak metabolic response (PMR) following NA injection was about 1-5 times greater in CD lambs than in the CL and WM lambs (P < 0-05). The mean elevation of PMR over thermoneutral metabolic rate was respectively: 2-8, 1-8 and 1-7 times in the CD, CL and WM lambs (P < 0-05), and this elevation was sustained for longer in the CD lambs (P < 0-01). Thus, the total metabolic response to NA was markedly greater in CD lambs.It was concluded that cold exposure during late pregnancy favoured the deposition of (or checked the normal decline in) foetal brown adipose tissue, so raising the neonatal capacity for non-shivering thermogenesis.

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“…Severe heat stress during the last third of pregnancy inhibits the growth of the placenta and foetus independently of any reduced feed intake (Alexander & Williams 1966;Brown et al 1977). The lower birthweight does not necessarily affect subsequent size, as it has been shown that lambs can catch up, but viability during the first 5 days following birth may be reduced (Shelton 1964). By the sixth day following parturition, both large and small lambs will have established greater tolerance to hyperthermia (Morgan et al 1972).…”

Section: Heat Stress and Shadementioning

confidence: 96%

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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Relation of Environmental Temperature During Gestation to Birth Weight and Mortality of Lambs

Cited by 38 publications

References 0 publications

Genetic parameters for lamb birth weight in spring and autumn lambing

Genetic parameters for lamb birth weight in spring and autumn lambing

The effect of environmental temperature during pregnancy on thermoregulation in the newborn lamb

The role of shelterbelts in protecting livestock: A review

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