ACUTE HEAT STRESS EFFECTS ON HEAT PRODUCTION AND RESPIRATION RATE IN SWINE

Sixteen Large White ×Landrace high-lean-growth barrows (83.5 ± 3.2 kg) were acutely exposed to one of four treatment temperatures (18, 24, 28, or 32°C) for a period of 22 h. The barrows had ad libitum access to feed and water during the experiment. During the 22 h exposure, CO2 production, O2 consumption, moisture production, feed intake and water intake were measured in an indirect calorimeter. Respiration rate was measured every 6 h by visual observation of flank movement. The calculated heat production was significantly affected by temperature and ranged from 695 to 560 kJ/(day kg0.75). Feed intake decreased at both 28°C and 32°C. Water intake increased only at 32°C. Moisture production increased slightly at 28°C; however the greatest increase was at 32°C. Respiration rate was affected by both temperature (P 0.1). The respiration rate increased exponentially with increasing temperature above 18°C.