Heat stress is known to alter the physiology of livestock, reducing production and male and female fertility, and increasing mortality rates. Animals’ water requirements increase with temperature. Heat stress suppresses appetite and feed intake. Body temperatures beyond 45–47 °C are lethal in most species. In general, the high-output breeds from temperate regions, which provide the bulk of market production today, are not well adapted to heat stress.
          Temperature is predicted to increase globally, with reduced precipitation in many regions, particularly in already arid regions (IPCC, 2007). In general, livestock can adapt to small increases in temperature without great problems. Nonetheless, it can be expected that in parts of the world, temperature increases associated with climate change will have a significant negative impact on levels of animal production unless management is adapted. Many local breeds in the tropics and subtropics are comparatively well adapted to high temperatures. For them, the main climate change-relate problems are likely to be associated with feed availability. Nonetheless, climatic conditions that induce heat stress are expected to become more frequent in Africa in the coming decades. Non-adapted animals introduced to the tropics are already often affected by heat stress, particularly where high temperatures are combined with high relative humidity and diets based on poor-quality forage.
          Options for alleviating heat stress include adjusting animals’ diets to minimize diet-induced thermogenesis (low fibre and low protein) or by increasing nutrient concentration in the feed to compensate for lower intake; taking measures to protect the animals from excessive heat load or enhance heat loss from their bodies; or genetic selection for heat tolerance or bringing in types of animals that already have good heat tolerance.
         A variety of techniques can be used to keep animals cool. Options include simple shading, natural ventilation of buildings, mechanical ventilation using fans to increase air flow, use of water sprinklers to wet animals and enhance evaporative cooling, or the use of misters to increase evaporative cooling of the air. All these options require some degree of initial investment, some require access to relatively advanced technologies, and all except simple shading require ongoing input of water and/or power. The practicality of implementing cooling measures depends on the type of production system. They can most easily be applied in systems where the animals are confined and where the necessary inputs can be afforded and easily accessed. In extensive grazing systems, it is difficult to do more than provide some shade for the animals and possibly places for them to wallow. It is also difficult to implement cooling measures for animals that have to move about a lot, such as those used for transport. Livestock producers in areas where relative humidity is high face additional problems as there is less potential for the use of methods based on evaporative cooling.
         Introducing technological adaptations to rising temperatures is relatively easy in industrial production systems where animals are confined and heavy use of external inputs is the norm. This may make such systems relatively insensitive to the local-scale effects of climate change and allow them to continue to raise high-output non-locally adapted breeds, provided rising input prices do not undermine the economic sustainability of the high external input strategies. Small-scale producers who have adopted high-output breeds, but struggle to obtain the inputs needed to prevent the animals from becoming overheated, may find that their problems are exacerbated by climate change.
         In addition to the physiological effects of higher temperatures on individual animals, the consequences of climate change are likely to include greater risk that geographically restricted breed populations will be devastated by the direct impact of extreme climatic events such as floods and hurricanes. The impact of past climatic disasters on AnGR diversity is also unclear. It is possible to find numerous reports of floods and hurricanes that have caused the deaths of tens or even hundreds of thousands of animals: (DesInventar online inventory system) of the effects of disasters.