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Ruminant Nutrition and Forage Utilization
Asian-Australasian Journal of Animal Sciences 1993;6(2): 275-279.
https://doi.org/10.5713/ajas.1993.275    Published online June 1, 1993.
Effect of environmental temperatures on heat production in dairy heifers differing in feed intake level
B. P. Purwanto, F. Nakamasu, S. Yamamoto
A study using dairy heifers was conducted to determine the effect of environmental temperature on heat production differing in feed intake level. The design consisted of three levels of feed intake (low, medium and high) and two environmental chamber temperature (15 and 30째C) with four replications in each treatment. Rectal temperature (RT), respiration rate (RR), heart rate (HR) and heat production (HP) were then measured. At the both environmental temperature, RT, RR and HR increased with the increase in feed intake level. The RT and RR also increased with the elevation of environmental temperature. The HP of 30째C was significantly higher (4.8-8.9%) than 15째C. The estivated metabolizable energy requirement for maintenance (MEm) was higher (p<0.05) at 30째C (554.7 kJ/kg0.75 d) than 15째C (464.9 kJ/kgd). It was suggested that the decreasing in productive efficiency under hot environmental conditions partly associated with the increase in HP, which associated with the change in heat loss mechanism from sensible path to evaporative path.
Keywords: Dairy Heifer; Environmental Temperature; Heat Production; Metabolizable Energy; Physiological Responses

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