家畜の体感温度に関する研究

Effective temperature for human being has been studied by many workers from various points of view. Although Discomfortable Index has been worldly utilized in many nations, we can not make use of this index for farm animals. Because the effective temperature will be based on the feelings of animals imposed by heat environments relating to control mechanism between body temperature and heat environment, and because it has been recognized that body temperatures and these mechanisms are very different in human being and farm animals.<br>An attempt has been, therefore, made since 1966 to find an effective temperature which would be appropriate for dairy cows.<br>Holstein cows from the herd of the Farm of Hiroshima University were selected. From spring through winter 3 cows for 26 days in the first years, 5 cows for 42 days in the second year and one cow for 26 days in the third year had been researched into rectal temperature, respiration rate (R. R.) and pulse rate twice daily respectively. As environmental elements dry-bulb temperature, wet-bulb temperature, globe temperature and velocity of wind had been measured simultaneously.<br>There is a fundamental problem araised as to how to express the feelings of animals imposed by heat environment. As the result of investigating the present data which were obtained from a long term observation and statistic investigation, the authors found that R. R. had closer correlation with heat environment than rectal temperature, and that R. R. preliminarily rised in accordance with the rise of environmental temperature and rectal temperature rised thereafter. The relation is shown in Tab. 1. It became, therefore, clear that the feeling of cows on heat environments would be expressed by her R. R., though INGRAM (1965) rather emphasized rectal temperature than R. R. in pigs.<br>In general the principal climatic factors which determine the stress imposed by heat environment are dry-bulb temp. (DBT) and wet-bulb temp. (WBT). From the present data WBT is more important than DBT, as there is greater correlation coef. between WBT and R. R. than that between DBT and R. R. For example in the data from the second year the correlation coef. between DBT, WBT and R. R. were r=0.80 (n=69, DBT 4.9-34.3°C) and r=0.83 (n=69, WBT 2.1-27.1°C). When the data with same levels in DBT and WBT ranging from 9.0-27.1°C were picked up and compared, the correlation coef. and the rate of R. R. increase were r (DBT: R. R.)=0.93, r (WBT: R. R.)=0.88, 1.6 (R. R./DBT 1°C) and 2.9 (R. R./WBT 1°C).<br>It is, therefore, recognized that WBT is weighted almost two times as large as that of DBT. When the scales of DBT×0.3+WBT×0.7, DBT×0.35+WBT×0.65, DBT×0.4+WBT×0.6 and DBT×0.45+WBT×0.55 were compared respectively, there was the closest agreement<br>between R. R. and the scale of DBT×0.35+WBT×0.65, but the difference was not significant in the scale and the scale of DBT×0.4+WBT×0.6.<br>It is very interesting that the scale is quite agreeable with the scale of BIANCA (1962).