Impact of simulated heat stress on growth, physiological adaptability, blood metabolites and endocrine responses in Malpura ewes under semiarid tropical environment

Abstract

The study was conducted to develop a simulated heat stress model for sheep depicting natural environmental conditions and to observe its impact on growth, reproductive performance, physiological adaptability, blood metabolites and endocrine responses in Malpura ewes. The experiment was conducted on 16 adult Malpura ewes for a period of 35 days. The animals were randomly divided into two groups of eight animals each (GI – control, GII – heat stress). The GII ewes were exposed to different temperature at different hours of the day i.e. 38°C at 1000–1100 hours; 40°C at 1100–1200 hours; 42°C at 1200–1300 hours; 43°C at 1300–1400 hours; 44°C at 1400–1500 hours and 42°C at 1500–1600 hours in a climatic chamber. Feed intake (P < 0.01), bodyweight (P < 0.05) and body condition score (P < 0.01) reduced significantly in GII as compared with GI ewes while water intake increased significantly (P < 0.01). All physiological responses also showed significant variation between the groups for treatment. In addition, all endocrine parameters showed highly significant (P < 0.01) variation for the treatment. Plasma cortisol increased significantly (P < 0.01) while T3 (P < 0.01) and T4 (P < 0.01) decreased significantly in GII as compared with GI ewes. Further, plasma oestradiol decreased significantly (P < 0.01) while plasma progesterone increased significantly (P < 0.01) in GII as compared with GI. Among the biochemical parameters, hemoglobin, packed cell volume, plasma glucose, total cholesterol, urea and blood urea nitrogen differed significantly between the groups. In addition, oestrus duration also significantly (P < 0.05) reduced in GII as compared with GI. Based on the results obtained from the study it can be concluded that simulated heat stress influenced the adaptive behaviour of sheep in terms of changes in physiological, blood biochemical and endocrine responses. Ultimately, their growth and reproductive performance are compromised during the process of adaptation to the simulated heat stress.

Influence of seasonal changes on physiological variables, haematology and serum thyroid hormones profile in male Red Sokoto and Sahel goats

“…On the other hand, the Sahel goats had high PCV and RBC during the HDS as compared to the CDS. This agrees with the findings of other studies in goats exposed to high AT (Hashem 2014;Indu et al 2014). This difference in heamatological response of Red Sokoto and Sahel goats is presumably due to variation in the physiological responses of goat breeds to the seasonal changes in the Guinea Savannah climate.…”

“…Both increase and decrease in erythrocytic parameters (PCV, RBC and Hb) due to increase in AT has been reported in livestock. The decrease is associated with enhanced water intake due to heat stress, while the increase is related to elevated loss of body fluid through heat stress induced evaporative heat loss (Marai et al 2007;Indu et al 2014). In the present study, both reduction and a rise in values of erythrocytic parameters were observed depending on breed.…”

“…T 3 :T 4 ) were lower in the HDS compared to the CDS and RAS. Similarly, the study of Indu et al (2014) and Ribeiro et al (2015) in goats demonstrated high T 4 and T 3 during the cold compared to the hot seasons. The reduction in serum concentration of T 4 and T 3 during the HDS could reduce metabolism and heat generation so as to prevent a rise in body temperature.…”

“…The low erythrocyte parameters in Sahel compared to Red Sokoto goats is probably due to the lower body temperature in the Sahel goats. As animal with low body temperature do not sweat and, thus maintain blood volume (Indu et al, 2014;Ribeiro et al, 2015). In addition, decrease in RBC has been reported in animals exposed to extreme cold and has been associated with reduction in the half-life of erythrocytes (Ruiz et al 2004).…”

<b>Effect of concentrate supplementation and time scales of evaluation on behavioral and physiological responses of pregnant ewes on grazing system

“…Once RT did not differ between the breeds (p < 0.05), the mechanism of respiratory thermolysis was used to remove excess heat received by adverse environment, maintaining the TR within physiological patterns. Similar findings were reported by Sejian, Maurya, and Naqvi, (2010) and Indu et al (2014). Among physiological parameters studied, the rectal temperature is one of the best indicators of thermal stress in an animal.…”