*8.6.1 Acclimation*

The animals phenotypic reaction to an individual stressor in the environment is known as acclimation [23]. However, it is uncommon for only one environmental variable to adjust over time in natural environments. Acclimatisation is the adaptation of an animal to a variety of stressors in its natural environment [12] as a result, acclimation and acclimatisation are not termed as an evolutionary adaptation or natural selection, which are characterised as changes that allow for preferred selection of animal on basis of phenotype and also based on their genetic component that is conceded down to the next generation. If environmental stressors are eliminated, the altered phenotype of acclimated animals will return to normal. On the other hand, Animals are genetically adapted to their climate on the basis of their requirements. In other words, it's a homeostatic system triggered by the endocrine system that cause impact upon the cellular activities, metabolic activities and further alteration in systemic, which permits the animals show adaptability towards heat stress and also overcome to it [12].

At consequence, acclimation can be thought of as a mechanism that occurs over the course of a lifetime, in which constant exposure to a specific stressor, such as extreme hot weather, causes biological changes, improving the fitness of the individual animal to live in climatic conditions [12]. There are three functional distinctions between acclimatory and homeostatic or "reflex" responses, according to Collier and Zimbelman [23].


As previously mentionesd, these acclamatory responses are typical of homeorhesis processes, and the net result is to synchronise metabolism in order to achieve a recent physiological state. As a result, the metabolism of the seasonally adapted animal differ in the winter from the summer. The Heat stress adaptation is thus, a homeorhesis process involving alter the patterns of hormonal signals that manipulate target tissue sensitivity to environmental stimulus. The improved genetic quality selection of heat stress tolerant genotypes would result from a better understanding of this mechanism.

### *8.6.2 Adaptation*

Adaptation is described as a biological change that occurs over generations as a result, of continuous stressor exposure and favours genetic assortment in an inhabitants to support species endurance [12]. For example Bos- indicus of tropical climates, earlier evolved in tropical climates with elevated temperature along with humidity as a result, they have a range of genetic variations that promote thermo-tolerance [12]. Thus, the ability of Bos-indicus breeds to survive in tropical environments on the basis of their requirements and adaptabilities towards it. They have evolved over generations. The climate conditions has the capability to oblige 'natural' selection for heat tolerant cattle in grazing breeding herds despite of assortment forces obligatory on the inhabitants. The generations are developing succeeding capacities to adapt them in warmth environment. The progenies developing heat resistivity potential with climatic circumstances. However, it is difficult to reach to conclusion in the case of bovine because of long interval in the productivity. When cattle come in contact of acclimation and adaptation the adapt the degree of resilience. The acclimation and adaptation, when covmbined with the use of mitigation options, which has the ability to improve cattle performance and productivity during the high heat stress.
