Chronic heat stress in Iranian fat-tailed ram lambs: clinical andparaclinical parameters

BACKGROUND: The effect of heat stress on physiological parameters has been well documented. However, there are reports of a genetic based heat tolerance in some sheep breeds. OBJECTIVES: The aim of the present study was to monitor the physiological responses of an Iranian fat-tailed breed against heat stress and an acute stress insult. METHODS:Atotal number of 15 fall-born ram lambs were selected and subjected to direct summer solar radiation throughout the day (May 2009 toFebruary 2010). Ten lambs were semi-castrated in October to see the physiologic response of animals to an acute stress. The general parameter as well as blood chemistry and cortisol were analyzed during the study. RESULTS: The results showed that all physiologic parameters had significant changes; however, theirvalues were in normal range. The fact that the animals in the present study experienced their first exposure of heat stress and a significant increase in serum cortisol concentration in semicastrated lambs in October, compared to the respected values in the hottest months of the experiment, may indicate a geneticbased adaptability of the breed in Iran. CONCLUSIONS: The present study shows the dynamic changes of general and biochemical parameters in response to chronic heat stress and an acute stress that raises a possible tolerance of the breed against heat stress

Keywords:

general examination , heat stress , ramlamb , serum biochemistry