Impact of Climate Change on Animal Health

Animals respond to change in environment through adaptation and climate through acclimation and in fact both, adaptation and acclimation are defined as the ability to adjust according to evolution.The phenomenon by which animal responds to any unexpected worse condition is stress.Acclimation is commonly a concern of various generations.Usually, two terminologies have been used in literature, heat load that is harsh environmental conditions and heat stress that is how animal responds such situations.Heat stress to animals especially livestock i.e., poultry, sheep, goat, horses, cattle & buffalo, is usually graded as no stress, mild stress, moderate level stress and severe stress.Persistent exposure to severe heat stress is attributed as animal abuse and against the objectives of animal welfare.Animals that are frequently exposed to severe stress, usually show relatively weak body conditioning scores, weak immunity, less production and reproduction potential, less feed intake, more fluid loss (sensible or insensible) and loss of cognition.Representative concentration pathway (RCP) from 4.0 to 5.0 and temperature humidity index (THI) <80 is considered as normal limits for livestock management and growth.Regions with less RCP and THI show reduced saturation of livestock.Sheep and goats are relatively more prone to heat stress and thus, there is decrease in caprine and ovine farming trend in hot regions like in Africa (Camberlin 2017).Heat stress induces more sweating, more peripheral circulation, elevated body temperature, less urination, polypnea, recumbency, tachycardia, less digestion, less fermentation in rumen, less metabolism, and ultimately overall less performance in animals.Observation of more somatic cell count and less protein content in milk indicates more prevalence of mastitis in dairy animals facing heat stress.Expression of heat tolerant genes with the passage of time and altered metabolic profile are good acclimations but unfortunately, may accompany expression of genes with less production.Abortions have been reported due to heat stress affecting blastocyst formation and embryonic implantation in cattle and buffalo.This window of abortions has been narrowed down by modern techniques in reproduction like in vitro fertilization and embryo transfer.Detrimental effects of higher THI values on spermatogenesis are reported in literature and proved a hinderance in the collection and processing of semen and compromising the viability of sperms.Stress can be estimated by feces, plasma, blood and hair cortisol levels for per acute, subacute, acute and chronic conditions.Estimation of cortisol levels doesn't confirm that stress is from heat in fact any stress condition can elevate cortisollevel.