Review: Adaptation of animals to heat stress

Abstract

Livestock plays an important role in the global economy. Climate change effects are not only limited to crop production, but also affect livestock production, for example reduced milk yields and milk quality, reduced meat production and reduced fertility. Therefore, livestock-based food security is threatened in many parts of the world. Furthermore, multiple stressors are a common phenomenon in many environments, and are likely to increase due to climate change. Among these stresses, heat stress appears to be the major factor which negatively influences livestock production. Hence, it is critical to identify agro-ecological zone-specific climate resilient thermo-tolerant animals to sustain livestock production. Livestock responds to the changing environments by altering their phenotypic and physiological characters. Therefore, survivability of the animal often depends on its ability to cope with or adapt to the existing conditions. So to sustain livestock production in an environment challenged by climate change, the animals must be genetically suitable and have the ability to survive in diversified environments. Biological markers or biomarkers indicate the biological states or alterations in expression pattern of genes or state of protein that serve as a reference point in breeding for the genetic improvement of livestock. Conventionally, identification of animals with superior genetic traits that were economically beneficial was the fundamental reason for identifying biomarkers in animals. Furthermore, compared with the behavioural, morphological or physiological responses in animals, the genetic markers are important because of the possibility of finding a solution to animal adaptability to climate change.

Floods, Hurricanes, and Other Catastrophes: A Challenge for the Immune System of Livestock and Other Animals

“…Another common response to heat stress in different farm animal species (cattle, goats, sheep, pig, poultry) is the increase in peripheral cortisol levels (19)(20)(21)(22). Indeed, the heat stress causes the activation of the two axes hypothalamic-pituitaryadrenal (HPA) and sympathetic-adrenal-medullar (SAM), with the final release of cortisol and catecholamines that are known to influence the biology of leukocytes.…”

Resilient capacity of cattle to environmental challenges – An updated review

“…Declined body size is one of the universal responses to warming beside variations in phenology and dissemination (Gardner et al 2011). Smaller body size of tropical indigenous cattle breeds is beneficial for surviving in harsh environments (Sejian et al 2018). In addition, changes in functional traits like body size have a significant consequence on thermal biology and energetics of ruminants, as body size directly affects energy requisite for maintenance, growth, and production (Mitchell et al 2018).…”

“…Similarly, Curtis et al (2017) reported that the dairy cattle seeking shade during heat stress increased their feed intake with high air temperature and solar radiation. However, tropical indigenous breeds were observed to be highly adapted to direct heat stress, spending more time for grazing than resting in shade (Sejian et al 2018).…”

“…Heat-stressed animal spend more time in standing posture in order to reorient themselves in different directions to avoid direct solar radiation and ground radiation. During thermal stress, animal upsurge evaporative heat loss in order to reduce the excess heat load from the body surface and assist in convection by standing more time to get away by the conductive and radiative heat from the surroundings (Kamal et al 2016;Sejian et al 2018). Even mild heat stress also result in increased standing time which may lead to lameness in cattle, when the animal stands for more than 45% per day (Tucker et al 2008).…”

Correlations between Environmental Factors and Milk Production of Holstein Cows

“…High air temperatures adversely affect the welfare and productivity of dairy cows during the summer, not only in tropical regions, but on most of the European continent. This is the cause of significant losses of livestock [1,2]. However, high temperature should not be considered the only factor leading to decreased cow milk yield in the hot period of the year.…”