Abstract for: A conceptual model to describe heat stress of dairy cows, from actual to questionable loops.

The thermal environment is recognized to be one the most important ecological factor to determine growth, development and productivity of domestic animals both for direct and indirect effects on physiology and behavior. Due to heat stress animals reduce milk production and fertility and increase the incidence of metabolic disorders, causing low revenues for the farm in the short and medium periods. Due to the world climate change more impact of the meteorological variables on animal responses is expected for the future. The aim of this work was to describe and understand the variables interactions associated with the heat stress of dairy cattle. The system thinking approach applied to this specific physiological mechanism might help to better focus managerial aspects related to grazing conditions and animal needs. The causal loop diagram annotation was used to connect the biological variables included in the system boundaries. Causal connections were validated with literature information. The most important feedback loops were highlighted to underline the dominant structure and the expected patterns. Four balancing loops were found to be involved in the physiological mechanisms used by animals in order to reduce metabolic heat production and to regulate the homeostasis of the internal temperature.