Milk production, mortality, and economic parameters in the context of heat-stressed dairy cattle.

Abstract As climate change progresses, higher temperatures and longer periods of extreme weather are likely to increasingly impact the production and health of dairy cattle, in turn affecting farm-level profits and economic decision-making. This review identifies and summarizes the currently available research on the effect of climate-related heat stress or heat stress mitigation measures on milk yield, mortality, and economic parameters on dairy farms. A scoping review approach was adopted to map the volume, range, and characteristics of the existing body of evidence and to identify research gaps. Through a comprehensive search, 286 studies published between 2010 and 2020 were identified and underwent data extraction and analysis. These studies were conducted in 46 countries, and encompassed both research and non-research herds as well as simulation models. The Temperature-Humidity Index (THI) was the most common indicator of heat stress, although a range of atmospheric, physiological, and descriptive indicators were used. Three-quarters of these studies examined at least one heat stress mitigation strategy, such as genetic manipulations, mechanical interventions, and diet manipulation. Approximately 97% of studies evaluated the impact of heat stress on milk yield, and 10% of studies examined at least one economic parameter. Research gaps exist in the analysis of economic parameters related to heat stress in dairy cattle. Given the urgent and increasing nature of climate challenges, additional economic analyses of the effects of heat stress in dairy cattle are needed to inform production and animal health decisions in a rapidly changing environment.