BSc- MSc (Integrated)

A study was conducted to evaluate the differences in the growth performance
and adaptive capabilities of three indigenous goat breeds (Osmanabadi, Malabari and
Salem Black) to heat stress challenges. The primary objective of the study was to
compare the growth performance and adaptive capacity 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 growth performance of these breeds were assessed based on BW changes,
allometric measurements, GH level and peripheral blood mononuclear cell (PBMC)
Insulin like growth factor-I (IGF-I) gene expression patterns while their adaptive
capabilities were assessed based on the changes in their metabolic and rumen
fermentation profiles. Thirty six ten months to one year old female goats of
Osmanabadi, Malabari and Salem Black breeds were randomly divided into six groups,
OC (n=6; Osmanabadi control), OHS (n=6; Osmanabadi heat stress), MC (n=6;
Malabari control), MHS (n=6; Malabari heat stress), SBC (n=6; Salem Black control)
and SBHS (n=6; Salem Black heat stress). The study was conducted for a period of 45
days. All group goats had access to ad libitum feed and water throughout the study
period. Heat stress group goats were exposed to summer heat stress for six hours from
10:00 h to 16:00 h while control group animals were kept in the shed protected from
heat stress. Breed factor significantly (P<0.05) influenced only few growth variables
such as BW, BMI, BCS. However, heat stress treatment significantly (P<0.05) reduced
all growth parameters expect BMI. Further, the heat stress significantly (P<0.01)
increased plasma GH concentration in goats with significantly higher (P<0.05)
concentration recorded in OHS. Among the stress groups, the lower (P<0.05) PBMC
IGF-I mRNA expression was recorded in OHS, while the higher (P<0.05) expression
was observed in SBHS. Significantly higher PBMC IGF-1 mRNA expression in Salem
black goats revealed the extreme adaptive capability of this breed as compared to other
breeds to heat stress conditions. Among the metabolic activity controlling hormones,
the breed factor significantly (P<0.05) influenced only plasma tri-iodo-thyronine (T3).
However, heat stress significantly (P<0.05) decreased thyroid stimulating hormone
(TSH) in both MHS and SHS groups while significantly (P<0.05) decreased the plasma
T3 in MHS. The rumen metabolites such as acetate, propionate, butyrate and total
volatile fatty acids (TVFAs) showed significant (P<0.05) variation for both breed and
treatment effect. The Salem Black breed did not show any significant variation for most
of the rumen metabolites as compared to both Osmanabadi and Malabari breeds for the
heat stress treatment. The results indicated that on comparative basis, Salem Black
breed adapted better to the heat stress challenges as evident from the non-significant
difference in circulating thyroid hormone levels and for most of the rumen metabolites
between the control and heat stress group in this breed. Further, it has been observed
that shifting of Malabari goats to the new location did not proved beneficial in terms
of improving their growth performance. In addition based on the alterations in rhythmic
metabolic activities, Salem Black goat breed exhibited higher adaptive capability to
heat stress than the other two breeds. Thus, it can be concluded from the study that
Salem Black breed was found to be superior in terms of both maintaining its productive
function as well as adapting to the adverse environmental condition by altering its
metabolic activities during heat stress exposure.
Keywords: BMI, BCS, heat stress, goat, growth, IGF-I, Kleiber ratio, T3, TVFA