Effects of Intermittent Short Term Acclimation to 32.DEG.C. on Some Thermoregulatory Responses and Standing Behavior of Laying Hens Exposed Acutely to 36.DEG.C..

Abstract

The experiment was conducted to determine the effects of acclimation to heat on thermoregulatory responses of laying hens when exposed to a new higher ambient temperature. The birds were subjected to non-exposure or exposure to 32°C from 1 to 3 days, and then all to 36°C ambient for 8 hours. Abdominal temperature, back skin temperature, shank skin temperature, heart rate, respiration rate, standing time and standing counts were measured during exposure period. When birds were exposed to 32°C, their abdominal temperature, back skin temperature, shank skin temperature and heart rate were greater on the 1st day than the 3rd day, and decreased obviously after lighting off, whereas respiration rate was lower on 1st day than 3rd day before lighting off and increased further for a short while after lighting off. At 36°C, abdominal temperature, back skin temperature, shank skin temperature and heart rate decreased with days of exposure to 32°C. Respiration rate of the birds unexperienced to 32°C did not increase further after lighting off. The unexperienced birds had markedly lower standing time and more standing counts than those of the experienced birds. These results showed that the effects of acclimation to heat on thermoregulation and standing-lying behavior are recognized when the birds were exposed to a high ambient temperature only for 3 days, and the standing behavior of chickens is clearly associated with thermoregulation at the high ambient temperature.