# EFFECT OF ENVIRONMENTAL TEMPERATURE ON HEAT PRODUCTION AND ITS ENERGY COST FOR THERMOREGULATION IN DAIRY HEIFERS

• Purwanto, B.P. ;
• Harada, M. ;
• Yamamoto, S.
• Received : 1993.06.14
• Accepted : 1993.11.17
• Published : 1994.06.01
• 38 3

#### Abstract

A study was conducted using four dairy heifers to determine the effect of 10, 20 and $30^{\circ}C$ environmental temperatures on the physiological responses and heat production, at a fixed level of TDN intake ($60.5\;g/kg^{0.75}\;d$). The analysis showed significant affects of environmental temperature on respiration rate (RR), mean body temperature (Tb), changes in body heat storage (S) and heat production (HP). The HP at $20^{\circ}C$ was almost the same as at $10^{\circ}C$, but the HP at $30^{\circ}C$ was 11% higher than at $10^{\circ}C$. A tendency for an elongation of standing time (ST) with the increase in environmental temperature was also observed. These results suggest that the increase in energy cost of elongation of ST ($9.2\;kJ/kg^{0.75}\;d$) and $1.3^{\circ}C$ increase in Tb ($17.3\;kJ/kg^{0.75}\;d$).

#### Keywords

Environmental Temperature;Heat Production;Standing Time;Mean Body Temperature;Dairy Heifer

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