Contents lists available at ScienceDirect Journal of Thermal Biology journal homepage: www.elsevier.com/locate/jtherbio Effect of thermal exposure on physiological adaptability and seminal attributes of rams under semi-arid environment Kalyan De ⁎ , Davendra Kumar, Krishnappa Balaganur, Vijay Kumar Saxena, Palanisamy Thirumurugan, Syed Mohammed Khursheed Naqvi Animal Physiology and Biochemistry Division, ICAR-Central Sheep and Wool Research Institute, Avikanagar, via Jaipur, Rajasthan 304501, India ARTICLE INFO Keywords: Thermal exposure Physiological response Semen Cortisol Semi-arid ABSTRACT Thermal stress in hot semi-arid environment is a major limitation of sheep production in tropical and sub- tropical climatic condition. The animals tend to maintain homeostasis through physiological adjustments in a hot environment (maximum temperature reaches up to 47.5 °C). Therefore, the present study was carried out to assess the effect of thermal exposure on physiological adaptability and seminal attributes of rams under semi- arid environment. The experiment was conducted for eight weeks involving sixteen Malpura crossbred rams (GMM: Garole X Malpura X Malpura). The rams were divided equally into two groups, designated as G1 and G2, respectively. The rams in G1 (Control) group were kept in a sheep shed under naturally prevailing environment without artificial manipulation of ambient temperature (Temperature 30.48 ± 0.38 °C; Relative Humidity 28.59 ± 1.15%). The rams of G2 group were exposed to different temperature at different hours of the day (38 °C at 1000–1100 h; 40 °C at 1100–1200 h; 42 °C at 12:00–1300 h; 43 °C at 1300–1400 h; 44 °C at 1400–1500 h and 42 °C at 1500–1600 h) in a climatic chamber for thermal exposure. Physiological responses, blood biochemical profile, blood endocrine profile, sexual behavior and seminal attributes were measured for both the groups. Thermal exposure significantly (P < 0.05) increased the water intake; respiration rate, rectal temperature and skin temperature at afternoon in rams. Exposure of rams to thermal stress (G2) significantly (P < 0.05) increased cortisol level and decreased tri-ido-thyronine level. The latency period after the first ejaculation, decreased significantly (P < 0.05) in G2. The percentage of rapid motile sperm, linearity and average path velocity of sperm were also altered significantly (P < 0.05) in thermal exposed rams as compared to control. However, comparable feed intake, body weight, and major blood biochemical parameters, as well as acceptable semen quality attributes of all the rams indicated that the Fec B gene introgressed Malpura cross rams adapted to the thermal exposure under semi-arid tropical climate. 1. Introduction Climate change is a major threat to the sustainable livestock production in many parts of the world (Gaughan and Cawsell-Smith, 2015). The hot semi-arid environment is a considerably large agro- climatic zone in both tropical and subtropical latitude with a dense indigenous sheep population (Kumar et al., 2015). The impact of climate change is predicted to be more alarming in the warmer part of the world relative to other regions, posing a greater challenge to sheep rearing. Moreover, it is well established that the high producing animals are more susceptible to thermal stress (Martello et al., 2010). Generally, sheep as homeotherms maintain their body heat balance by dissipation of excess heat from their bodies when exposed to elevated ambient temperatures (Sejian et al., 2010b). Exposure to high ambient temperatures further increases the effort to dissipate body heat, resulting in increase of respiration rate and body temperature (De et al., 2014). Respiratory evaporative cooling is employed more prominently for heat dissipation than sweating as wool coat reduces the ability of evaporative cooling (Marai et al., 2007). The skin serves as a large dissipative surface organ for the heat exchange between the body and the environment (Adboun et al., 2012). When the dissipative equilibrium of this heat exchange is altered, it is reflected in terms of altered rectal temperature (McManus et al., 2009) as well as the variations in physiological parameters, hormone secretion and blood metabolites (Marai et al., 2006). In tropical and subtropical areas, indigenous sheep tend to breed throughout the year, although sexual activity is slightly contained during the summer months (Marai et al., 2004). Heat stress is the http://dx.doi.org/10.1016/j.jtherbio.2017.02.020 Received 15 February 2016; Accepted 24 February 2017 ⁎ Correspondence to: Adaptation Physiology Laboratory, Division of Animal Physiology and Biochemistry Division, ICAR-Central Sheep and Wool Research Institute, Avikanagar 304501, Rajasthan, India. E-mail address: kalyande2007@gmail.com (K. De). Journal of Thermal Biology 65 (2017) 113–118 Available online 02 March 2017 0306-4565/ © 2017 Elsevier Ltd. All rights reserved. MARK