There is a paucity of reliable information pertaining to the combined effect of environmental temperature and relative humidity on growth measured as body weight gain during the juvenile stage as an expression of productive adaptability. Hence, the effects of different combinations of temperature and humidity were studied on 1507 mice in 19 experimental groups. The environmental temperature had a decisive non-linear effect on body growth. Large growth depressions were observed above 30-degrees-C and non-significant ones between 20-degrees-C and 30-degrees-C. The highest weight gain was observed at 25-degrees-C and 70% relative humidity. The effects of relative humidity in combination with environmental temperature were less than it has been presumed so far. Cumulative or compensatory effects of these environmental factors on growth were not observed. The of joint consideration live weight gain and water vapour partial pressure did not change this result. Existence of critical temperature at the accepted level was confirmed. However, the negative effects of high environmental temperature on growth are not reduced by lower relative humidity.
