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Published online by Cambridge University Press: 02 September 2010
Eight Merino wethers were used in an experiment designed to study the effect of heat stress on ruminal activity and blood urea of sheep newly introduced to Egypt. The sheep were exposed to 15° and 35°Cin aclimatic chamberwith controlled temperature and humidity. The animals were divided into two groups; the first received 100% of the TDN daily requirement and the second was given 125% of the recommended TDN. Rumen and blood samples were obtained from the animals before and at 2, 4, 6, 8 and 10 hr after feeding.
VFA concentrations in the rumen were higher in sheep fed on rations of high energy content. The levels of VFA at the low temperature were greater than at the high temperature. Ruminal ammonia and blood urea N concentrations in sheep maintained at the low temperature (15°C) were higher than those of the same animals when kept at the high temperature (35°C). This trend was more obvious at high levels of energy intake. It is suggested that the significant changes in rumen VFA, ammonia N and blood urea N in Merino sheep maintained under hot conditions can be considered as adjustments to changes in nutritional requirements in response to high environmental temperature.