549Effects of acute heat stress on changes in the rate of liquid flow from the rumen and turnover of body water of swamp buffalo SUMMARY During 5 h of acute heat exposure (41 °C), there were increases in the heart rate from 43±2 (S.E.) to 51 ± 1 beats/min, respiratory rate from 26±4 to 86± 16 breaths/min and rectal temperature from 385 + 0 1 °C to 39-7 + 0-2 °C. The flow rate of liquid from the rumen and body water turnover significantly increased while biological half life of ehromium-51 ethylenediaminetetra-acetate in the rumen and tritiated water decreased from 12-9±2-5 and 87-7 + 6-8 h to 9-3±20 and 49-2±5