BSc-MSc (Integrated)

A study was conducted to evaluate the differences in the thermo-tolerant abilities of
three indigenous goat breeds (Osmanabadi, Malabari and Salem Black) to heat stress
challenges. The primary objective of the study was to compare the adaptive ability of two
indigenous goat breeds (Malabari and Salem Black) when they were shifted from their native
tract to a new agro-ecological zone with the local breed (Osmanabadi) during heat stress
exposure. The adaptive capabilities of these breeds were assessed based on the changes in
their behavioral, physiological, blood biochemical and endocrine responses and peripheral
blood mononuclear cell heat shock protein 70 (PBMC HSP70) gene expression patterns.
Thirty six 10 months to one year old female goats were randomly allocated into six groups of
six animals each as OCON (n=6; Osmanabadi control), OHS (n=6; Osmanabadi heat stress),
MCON (n=6; Malabari control), MHS (n=6; Malabari heat stress), SCON (n=6; Salem Black
control) and SHS (n=6; Salem black heat stress). The OCON, MCON and SCON animals
were maintained in the shed while OHS, MHS and SHS animals were exposed to summer
heat stress between 10:00 h to 16:00 h. All the animals had access to ad-libitum feed and
water. The duration of the study was 45 days. Results indicated that among the behavioural
variables studied, both drinking frequency (DF) and water intake (WI) were significantly
higher (P<0.01) in heat stress groups of all the three breeds as compared to their respective
control groups. Further, significantly lower (P<0.05) urinating frequency (UF) and higher
(P<0.05) rumination time (RuT) was recorded in MHS as compared to other stress groups.
The heat stress treatment significantly (P<0.05) lowered the respiration rate (RR) and rectal
temperature (RT) in the morning while significantly (P<0.01) increased all the physiological
variables such as RR, pulse rate (PR) and RT in all the three breeds during afternoon. Further,
the results indicated that only breed differences (P<0.01) were established for different
biochemical variables in the study while the heat stress did not alter these parameters.
However, heat stress significantly (P<0.05) increased the plasma cholesterol in MHS group
while significantly lowered (P<0.05) plasma triglyceride in both OHS and SHS groups.
Further, aspartate aminotransferase (AST) showed significant variation for both breed
(P<0.05) as well as treatment (P<0.05) effect. In addition, heat stress significantly increased
(P<0.01) plasma cortisol and significantly decreased (P<0.05) plasma aldosterone in only
MHS group. Furthermore, heat stress induced PBMC HSP70 expression was significantly
higher (P<0.05) in OHS and MHS as compared to SHS group. Thus, it can be concluded
from the results that although Malabari breed which is well known for its survival in harsh
environment in its native tract could not adapt well to the new locality with much lower
magnitude of heat stress. The less severe influence of heat stress on the various biological
functions of Salem Black breed as compared to other two breeds clearly indicated the
superior adaptability of this breed to survive in different agro-ecological zones. Further, the
study also identified RR, RT, plasma cortisol and PBMC HSP70 to be the reliable biological
markers for evaluating the thermo-tolerant capacity of indigenous goat breeds.
Keywords: Adaptation; Climate change; Cortisol; Drinking frequency; Goat; Heat stress;
HSP70