EnvironmentPhysiology
The environment can be defined as the surroundings or conditions in which humans, animals, or plants live or operate. The environment is critical to life on the planet earth. An ecosystem refers to all the living and non-living things that exist in an ecosystem and the ecosystems’ relationship to one another.
It is the foundation of the biosphere, which governs the overall health of the planet. To make things simple, the environment can be classified into two parts: the biotic environment, which includes all living organisms such as animals, forests, bacteria, fungus, and so on, and the abiotic environment, which includes all non-living components such as temperature, humidity, water vapour, and air. Since industrialisation era human activities from pollution to overpopulation drive up the earth’s temperature and fundamentally change the world around us. The leading cause is a phenomenon known as the greenhouse effect. Various gases surrounding the atmosphere, namely water vapour, carbon dioxide (CO2), methane, nitrous oxide, and chlorofluorocarbons, let the sunlight enter the atmosphere but keep the radiated heat from escaping the earth’s surface the glass walls of a greenhouse. The greater the concentration of greenhouse gases in the atmosphere, the greater the amount of trapped heat, strengthening the greenhouse effect and increasing the earth’s temperature. Global warming has accelerated as a result of the rapid rise in greenhouse gases in the atmosphere. Climate change has repercussions on the oceans, the weather, food supplies, and human and animal health. Ice sheets such as Greenland and Antarctica are melting. Sea levels rise due to the excess water once contained in glaciers spilling out into the oceans, swamping coastal regions. Furthermore, more intense storms, flooding, heavy snowfall, and droughts incidents are getting more common. These fluctuations in the weather present difficulties; cultivating crops becomes more challenging.As mentioned, environment plays a significant role in the productivity of an animal. In this changing environment, the animal gets exposed to different stressors, like heat stress, nutrition stress, walking stress, water stress, transportation stress, and many more. Animals have evolved mechanisms to manage short-term stressors. During the short-term exposure, the biological cost is minimal because adequate reserves of biological reserves exist to cope with the stressor and meet the impact of the stress without any disturbances on biological functions. If the animal gets challenged by multiple stressors, there will be insufficient biological reserves to satisfy the biological cost of the stress response; to counteract this, resources will be channelled from other biological functions. As shown in Fig. 1.7, when resources are sidetracked from productive functions, it leads to impairment of biological functions. For example, when multiple stresses deplete body reserves, metabolism shifts away from growth, the young animal no longer blooms, and growth is restricted. When energy is shifted from reproduction and its process, reproductive success is reduced. This metabolic maintenance behaviour of an animal’s body rather than production will last until the animal restocks its resources/reserves sufficiently to re-establish normal functions.
Livestock acts as a significant contributor to global food security, particularly in fringe lands where livestock is characterised as a protein, energy, and micronutrient source. Global climate change has a considerable effect on the livestock sector, depending on different ecosystems and natural resources. Looking at the different climate change predictions, we can envision the future of the great struggle to adjust and adapt to new environmental challenges both by humans and livestock. To ensure food security, policymakers and researchers should prioritise identifying animals with superior genetic traits that are economically beneficial and identifying biomarkers for a solution to animal productivity loss due to climate change, especially when animals are exposed to multiple stressors.
As mentioned previously, homeostasis is a mechanism that maintains physiological stability through interaction between internal processes and the external environment. One of the routes to achieve is through thermoregulation. Thermo conformers and thermo regulators are the two types of organisms. The internal temperature of thermo conformers depends on the external environment, whereas thermo regulators maintain their internal body temperature within a particular limit, still being responsive to external stimuli. There are a variety of reasons that contribute to the distinction in temperature regulation among organisms. These include adaptation, mutation, and environmental stimulation. There are different adaptation strategies developed during their lifetime to maintain the desired body temperature.
Fig. 1.7 Pictorial representation of summation effect of multiple stresses in goats. (Source: Sejian et al. 2018)
On exposure to heat stress few animals loose heat through sweating (e.g. horses, humans). Rats, mice, dogs, and cats all have sweat glands on the soles of their feet. Rather than that, many mammals (e.g. dogs) pant to cool themselves. Vasodilation is another method of releasing heat from the body. Those blood vessels closest to the skin’s surface expand wide and allow blood to flow through them. Blood gets cooled down as the heat radiates out of the body. In contrast to heat loss, animals employ the opposite mechanisms to retain heat when the ambient temperature falls below the core body temperature. Vasoconstriction is accomplished by subdermal capillaries, which redirect blood away from the skin and body’s periphery. In extreme cold, prolonged blood rerouting away from the extremities results in numbness and cellular damage (e.g. frostbite). Animals contract minute subdermal muscles (erector pili) to erect dermal hair follicles to increase heat retention. These erect hairs form a heat-trapping insulating layer.
1.10