Recent investigations by the Australian Department of Agriculture, Fisheries and Forestry into high
mortalities on live export voyages from Australia to the Middle East during the Northern hemisphere
summer suggest that animal welfare may be compromised by heat stress. The live export industry has
generated a computer model that aims to assess the risk of heat stress and to contain mortality levels
on live export ships below certain arbitrary limits. Although the model must be complied with under
Australian law, it is not currently available for independent scientific scrutiny, and there is concern that
model and the mandated space allowances are inadequate. This review appraises the relevant literature
on heat stress in sheep and cattle, including laboratory studies aimed at mimicking the ambient
temperatures and humidity levels likely to be encountered on live export voyages. Animal welfare is
likely to be very poor as a result of heat stress in some shipments.