Strategies to ameliorate heat stress effects on sheep reproduction

The reproductive performance of sheep will be challenged by increasing temperatures and more extreme weather events due to climate change. Heat stress potentially reduces the mating behaviour and fertility of ewes and rams, while increasing embryonic mortality, impairing fetal development and reducing lamb birth weight, and increasing perinatal lamb mortality. Heat stress can occur above 32 °C, but the degree, duration, and timing of heat stress determines whether reproductive performance is reduced, and to what extent. This chapter considers practical husbandry and nutritional interventions to optimise sheep reproduction in extensive grazing systems. Strategies include genetics, choice of month of mating and lambing, shearing date, provision of shade, nutritional supplements and targeted nutrition.