Heat production and body temperature of Bos taurus x Bos indicus crossbred cattle in the humid tropics

A study was conducted to examine how well Bos taurus x Bos indicus; crossbred cattle adapt to the humid tropical conditions in Malaysia. The present paper reports the heat production (HP) and body temperatures (Tb) of the indigenous Kedah-Kelantan (KK) and Charolais x KK crossbred (CK) cattle kept in-door (ID) and out-door (OD). Heat production, rectal temperature (Tr), mean skin temperature (Ts) and mean body temperature (Tb) of the test cattle were measured at 10 regular intervals for 24 hours. The crossbred cattle exhibited a distinctly lower HP (ranged between 17.2 to 27.1 kJ/kg(0.75)/h) than the indigenous KK cattle (ranged between 33.0 to 45.0 kJ/kg(0.75)/h), irrespective of feeding levels and environmental treatments. Tb of cattle exhibited diurnal variation, high during the day and low during the late evening through to the early morning. Tb of ID cattle fluctuated in a narrow range between day and night (averaged 0.7 degrees C and 0.9 degrees C, respectively for CK and KK), while the fluctuation of Tb for OD cattle was more pronounced, averaging 1.7 degrees C and 2.2 degrees C respectively for CK and KK. The results of the present experiment indicated that CK crossbred cattle adapted to the hot and humid environments. They do so by maintaining a lower metabolic rate, and by their ability to quickly expel the excessive body heat, whenever their own micro-environment was favourable.