Given the global climate warming and the intensive genetic selection for high milk production, it seems that reduced fertility will become a limiting factor for the dairy industry in the coming years. The term “global warming” expresses various climate changes, such as rising sea levels, increased heat content of the oceans, decreased snow and ice surface coverage, and very intense rains. A prominent feature which directly affects the animal is the increase in the environmental temperature, expressed by an increase in the number of consecutive hot days (i.e., daily temperature higher from the average annual temperature) and increased frequency of extremely hot days (i.e., daily temperature higher from the average temperature of the hot season) (IPCC, 2014). For instance, an increase in summer temperatures, hot days, and heat waves have been recorded in Europe (Zampieri et al., 2016). Heat waves are defined as a sequence of at least 6 d with air temperature higher than the reference values for the period and the geographical area. The waves are classified according to their duration and/or their intensity and are known to cause extreme losses to the dairy industry (for review, see Pasqui and Giuseppe, 2019).
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