[in Japanese]

View full abstract

The effect of air temperature, air movement, snowfall and rainfall and direct solar radi-ation on heat loss from a heat loss simulator for a young calf were examined. The heat loss simulator, a cylindrical in shape was coverd with tanned calf fur and filled with an ethyleng-lycos solution controlled at 39℃. Heat loss from the simulator exposed to a cold outdoor envi-ronment was measured by heat flow transducers. Direct solar radiation reduced heat loss remarkably. A regression equation was derived relating heat conductance of the simulator to wind velocity and was found to be linear. A multiple regression equation to predict heat loss from the simulator from air temperature and wind velocity was also derived. The coefficient of deternination (R^2) of the equation was 0.756. Heat conductance of the simulator increased dur-ing snowfall and rainfall. The effedt of rainfall on conductance was greater than that od snow-fall. Dry powderlike snow hsd little effect on conductance. JAP.J.Livest.Management, 25(2) : 47-53.1989. Received June 19,1989.

View full abstract

To evaluate the role of heat production (HP) and evaporative heat loss (EHL) in themoregu-lation and to estimate the relation between EHL and respiration rate (RR) under short-term heat exposure, HP, EHL, RR and rectal temperature (RT) of four laying hens were measured at four levels of environmental temperature (Te), i. e. 24,29,31 and 34℃, using an open-circuit apparatus. At Te from 24 ℃ to 34 ℃, HP did not chenge significantly, which suggests that short-term heat exposure did not exert a direct effect on HP. EHL increased with Te which resulted in the ratio of EHL to HP increasing significantly. When RR increased to 172/min at 34 ℃, 40% of HP was dissipated by evaporation. At 31 ℃, all of the hens panted intermittently and EHL in-creased rapidly. The relationship between RR and EHL was Y=2.92+0.026X, (r=0.94,Y : EHL, kJ/kg^<0.75> h ; X : RR, /min). RT increased at 31 ℃ when panting was induced. The results suggest that the increase of EHL plays an important role in thermoregulation at high Te and EHL can be estimated from RR. Key words : evaporative heat loss, respiration rate, heat production, temperature, hen Jap.J. Livest. Management, 25(2) : 55-58.1989. Received June 21,1989.

View full abstract