ENVIRONMENTAL STRESS
Stress within the microenvironment of an animal arises due to the interplay among crucial interacting biotic and abiotic factors, stress level, the extent and duration of variations, and the energy or resources accessible to manage stressors.
The interconnections among these elements significantly influence the array and variety of animals present in that environment, as well as the specific type of evolutionary selection that takes effect (Wilmer et al. 2009). Abiotic environmental stress, defined as the negative impacts of non-living factors on living organisms under a specific environment, also affects the pasture and forage availability to livestock (Dawson et al. 2014). Despite the neutralising tendency of the vegetation, the introduction of an animal into an area also alters local conditions by adding excretory by-products (such as CO2), depleting oxygen, and modifying humidity and temperature levels. Consequently, an environment hosting an animal undergoes distinct changes compared to its state before the animal’s presence. Environmental stress such as drought, high/ low temperature, ozone, elevated CO2, soil water logging, and salinity reduces the productivity and health of livestock in all phases of production resulting in significant economic losses. Under field conditions, most of the time, the multiple stresses, i.e., heat stress, nutritional stress, water stress, and walking stress, occur in combinations and simultaneously cause a cascade of stressful conditions and ultimately culminating in serious health anomalies. The outcomes of multiple stress include decreased growth, body weight, production potential, reproductive performance and increased susceptibility to diseases.Environmental stressors induced by climate change encompass diminished availability of feed and water, alterations in temperature, and an escalation in extreme weather events.
Anticipated global climate change is expected to impact temperature, precipitation, atmospheric CO2 concentrations, and water availability which will likely influence the productivity of both crop and livestock systems (Hatfield et al. 2008). Instabilities in the atmospheric concentrations of various greenhouse gases, namely carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulphur hexafluoride (SF6), impact the earth’s capacity to absorb radiation. These greenhouse gases trap infrared radiation by reflecting it from the surface, functioning akin to a thermal insulating layer that sustains warmth within the planet’s atmosphere. Over the past 250 years, the concentrations of these greenhouse gases have markedly increased, primarily attributed to the amplified utilisation of fossil fuels which potentially induces indirect alterations in the hydrologic cycle. Environmental stressors have the potential to disrupt an organism’s internal equilibrium, resulting in physiological alterations that can either be advantageous or disadvantageous. The individual response to these stress-inducing factors is influenced by various determinants, including species, breed, prior exposure to the stressor, health condition, performance levels, body condition, metabolic status (such as pregnancy or lactation), mental state, and age (Figure 24.1). Adding complexity, stressors may manifest as acute (sudden changes), typically short-term alterations spanning hours to days or chronic (prolonged exposure), spanning weeks to months. Animals exhibit distinct responses to acute and chronic stressors by employing behavioural strategies as an initial defence, resorting to intricate and resource-demanding physiological adaptations only when behavioural strategies prove ineffective. Although acute responses play a crucial role in adaptation and aiding survival, chronic stressors prompt supra-physiological reactions that potentially contribute to health hazards (Sejian et al. 2010). At higher limits, stress triggers diverse neuroendocrine responses in animals, initiating the activation of various hormonal pathways and the release of regulatory hormones. Changes in the hormonal balance primarily involve a decrease in anabolic hormones and an increase in catabolic hormones. These alterations can serve as potential indicators of physiological changes within an animal’s body (Bernabucci et al. 2010).24.3
Source:
Rana Tanmoy (ed.). Principles of Veterinary Animal Physiology. CRC Press,2026. — 290 p.. 2026
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