Effect of thermal stress on livestock production: phenotypic and genetic analysis

Thermal stress is a research area of growing interest because of its effects on animal performance and animal production practices. The impact of adverse environmental conditions is caused by one combination of different environmental factors such as temperature, humidity, solar radiation, precipitation and air movement.The higher amount of studies about the impact of thermal stress found in literature provided a clear overview of the phenomena on dairy cows, pigs and poultry. Currently, the intensive selection on production has been increased the sensitivity of most productive species to thermal stress. Especially in dairy cattle there is a strong genetic antagonism between the level of production and heat tolerance joint to a high genomic/environmental (GxE) interaction between dairy production under cold, comfort and hot periods. The thesis is organized in five main chapters in which the effect of different environmental stressors was considered to evaluate the magnitude of thermal-impact on different traits of economic interest among three livestock species (sheep, beef cattle, and pigs). Each study was conducted considering different production systems characterize by distinct climatic and environments conditions. In addition, for beef cattle and pigs the genetic component of thermal response were estimated in order to explore the existence of GxE interactions across the wide thermal range endured by these animals.