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

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. 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. A total number of 15 fall-born ram lambs were selected and subjected to direct summer solar radiation throughout the day [May 2009 to February 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. The results showed that all physiologic parameters had significant changes; however, their values 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 genetic based adaptability of the breed in Iran. 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

Stereological study of Arabian ram testis during different seasons

Quantitative microscopic structure of testis in adult Arabian rams, raised under closed grazing system in Khuzestan province of Iran, was studied in four seasons over a one year period. For this purpose, thirty adult rams were randomly selected and the live weight and scrotal circumference of rams were recorded. At the beginning of each season, among the study group, four rams were randomly selected, slaughtered and their left testes were removed and weighed. For microscopic studies, tissue samples were excised from the left testes, fixed in Bouin's solution and embedded in paraffin. Cross-sections [5 micro m thickness] were stained with haematoxylin-eosin and evaluated with quantitative techniques. The results showed that scrotal circumferences, weight and volume of testis varied significantly throughout the year, with the lowest values in early summer [P<0.05]. Seminiferous tubule diameter was highest in early winter [220.97 +/- 12.15 micro m]. Also, relative and total volumes of seminiferous tubules and germinal epithelium gradually increased during the summer and autumn, with highest values in early winter. Higher relative volume of seminiferuos tubuli lumina [P<0.05] was found in early summer [%12.15 +/- 0.35]. Lower relative volume of interstitial tissue [P<0.05] was found in early winter [%15.70 +/- 0.49]. Scrotal circumference was significantly correlated with the seminiferous tubule diameter and the total volume of seminiferous tubules [r = 0.70, P<0.01]. The results indicated that the stereological structure of testis in Arabian rams raised under closed grazing system in the Khuzestan province of Iran is highly affected by season