Veterinary Physiology-III

ADAPTATION

• It is the adjustment of an animal to given environment. When the animals are continuously exposed to major environmental changes, they may develop functional and structural changes that results in an increase in their ability to live without stress in a new environment. This is called as adaptation.
• There are different types of adaptation:
  • Genetic adaptation
    • It refers to the heritable animal characteristics that are transformed from one generation to the other, which favour survival of a population in a particular environment. This may involve evolutionary changes over many generations (selection by nature) or acquiring specific genetic properties (selection by man).
  • Physiological adaptation
    • It is the capacity and process of adjustment of the animal to itself, to other living material and to its external physical environment.
  • Biological adaptation
    • It refers to the changes with respect to morphological, anatomical, physiological, biochemical and behavioral characteristics of the animal which promote welfare and survival of the animal in a given environment.
  • Phenotypic adaptation
    • These are the changes that occur during the life time of an individual. These are non heritable and it is the irdividuals response to the environment with accompanying changes in the genotype. Phenotypic adaptation can be physical as in callous formation on the hands and feet or behavioral as in taming of wild animals.
  • Nutritional adaptation
    • It is associated with both genetic and physiological adaptation. It occurs as a result of climatic and ecological changes. For instance, in the coastal areas of the tropical regions the soil and water are low in calcium and due to heavy monsoon rains the soil is leached out with a loss of calcium. This is reflected in the pastures with low levels of this mineral.
    • The low calcium intake by the animals lead to low serum calcium concentrations, but the tropical animals appear to be tolerant of this and surfer no ill effects.

Acclimatization

• It refers to long-term adaptive physiological adjustments, which results in an increased tolerance when exposed to continuous or repeated climatic stressors (normally produced under field conditions). E.g., if an animal voluntarily migrates from a mountain valley to a high altitude, its lung ventilation rate typically will increase initially to acquire adequate oxygen.
• Within few days or weeks, lung ventilation begins to drop back towards the sea level rates as other physiological mechanism that facilitates gas exchange at high altitude begins to operate. After several days the individual is said to be acclimatized to a new high altitude conditions.
• If an animal physiologist places that same animal in a hypobaric chamber, thus simulating high  altitude  conditions  the animal  becomes  acclimated  to  experimental "conditions in a few days. 
• Characters of well adapted animals:
  • There must be minimum weight loss when exposed to some stressors like nutritional deficiency, high milk production even when animals are transported.
  • It must have high reproductive rate.
  • It must have high resistance to diseases.
  • High longevity and low mortality.

Acclimation

• It refers to the adaptive changes that take place in response to a single climatic variable.(normally produced in a climatic chamber).