MSc

A study was conducted to assess the combined effect of heat stress and
nutritional restriction on growth and reproductive performances in Osmanabadi
Bucks. Twenty four adult Osmanabadi bucks (average body weight (BW) 16.0 kg)
were used in the present study. The bucks were divided into four groups viz., C (n=6;
control), HS (n=6; heat stress), NS (n=6; nutritional stress) and CS (n=6; combined
stress). The study was conducted for a period of 45 days. C and HS bucks had ad
libitum access to their feed while NS and CS bucks were under restricted feed (30%
intake of C bucks) to induce nutritional stress. The HS and CS bucks were exposed to
solar radiation for six hours a day between 10:00 h to 16:00 h to induce heat stress.
The data was analyzed using repeated measures analysis of variance. There were
significantly (P<0.01) higher standing time in ad libitum (C and HS) fed groups as
compared to restricted fed (NS and CS) groups. However, the highest (P<0.01) lying
time was recorded in CS group. The highest (P<0.01) drinking frequency was
recorded in CS group while the lowest in NS group. The highest (P<0.01) defecating
frequency was recorded in C group while the lowest in CS group. The highest
(P<0.01) water intake was recorded in both HS and CS groups. The animals exhibited
different physiological adaptive behaviour in morning and afternoon. The respiration
rate (RR), pulse rate (PR) and rectal temperature (RT) were higher (P<0.01) in ad
libitum fed groups in morning while in the afternoon it was higher (P<0.01) in both
HS and CS groups. Both skin temperature of head and scrotum in afternoon differed
significantly (P<0.01) between the groups. The highest plasma total protein (P<0.01)
and total cholesterol (P<0.05) was established in NS groups as compared to other
groups. Plasma triglycerides, plasma urea and plasma urea nitrogen also differed
significantly (P<0.01) between the groups. Further, the higher plasma cortisol
(P<0.01) and aldosterone (P<0.05) was recorded in CS group as compared to othergroups. The higher expression of adrenal Heat Shock Protein 70 (HSP70) messenger
Ribonucleic acid (mRNA) was reported in CS goats. However, the higher expression
of hepatic HSP70 mRNA was reported in HS goats. The highest degree of
degenerative changes and hyperactivity of endocrine cells was recorded in CS group
liver and adrenal gland respectively. It can be concluded from this study that when
two stressors occur simultaneously, they may have severe impact on adaptive
capabilities of Osmanabadi bucks as compared to that would occur individually. This
is evident from the significantly higher behavioural, physiological responses and
endocrine responses in CS group. Further, the study indicated that Osmanabadi bucks
possess the capability to adapt to the detrimental effects of environmental stresses
which is evident from the significant interaction of treatment and experimental days
on majority of the parameters studied.