Thermoregulatory Responses of Swamp Buffaloes and Friesian Cows to Diurnal Changes in Temperature

Abstract

It is well known that the rectal temperature of buffaloes is easily influenced by their surroundings. In our previous observation, the rectal temperature of buffaloes fluctuated over a 1.4 2.0°C range in rest conditions with seasonal changes of air temperature, while that of cattle remained constant in the same conditions. Rectal temperature of buffaloes decreased to 36.8°C at an air temperature of 7.0°C. (Koga et al., 1991). It has been suggested that a fluctuation of rectal temperature is an adaptation to ambient temperature change in some species (Johnson, 1971) and a major indicator of the failure of this adaptability in beef cattle (Moran, 1973). Buffaloes which live in a hothumid climate and have a unique behavior, namely, wallowing, have a physiological mechanism supporting heat dissipation when they wallow, viz. an increase in the blood volume and rate of blood flow to the skin surface in hot conditions (Koga et al., 1998). Therefore the present study was undertaken to clarify the effects of a diurnally changing environmental temperature on thermoregulatory responses of buffaloes and to suggest their implication in the thermoregulation. Three female swamp buffaloes (estimated to be 13 to 19 years old) and three Holstein-Friesian cows (dry and non-pregnant, 2 years old) were used in this study. Their average body weight at the beginning of the experiment was 510 and 650 kg, respectively. The experiment consisted of three successive periods as follows: period-1, constant temperature (30°C, 60%RH), period-2, diurnally changing temperature when temperature fluctuated between 25°C and 35°C (mean 30°C) with a constant 60%RH and period-3, diurnally changing temperature and humidity as well as period-2 the animals were fasting. During period-2 and 3, the temperature changed sinusoidly from 25°C at 00:00 to 35°C at 12:00 and then back to 25°C at 24:00. Measurements were done 9 times every three hours on the last day on each period. Measurements of rectal temperature, respiration rate and heart rate were recorded using conventional methods. After recording physiological parameters, exhaled gas was collected through a face mask for the measurement of respiration volume and heat production. After each measurement, food was given one of nine equal meals equally spaced over the day, except for period-3. Water was supplied ad libitum throughout. In buffaloes a significant correlation between rectal temperature and diurnally changing temperature was observed (P<0.05), while no sure correlation were observed for cows. Although rectal temperature in buffaloes fluctuated markedly during period-2, mean values over 24 hours were not significantly different between species. This result in buffaloes was because of the greater amplitude and the lesser maximum value in the rectal temperature in comparison with cows. Heat production in buffaloes was lower than in cows throughout the three periods. In comparison between period-1 and 2, an increment of mean heat production was lower in buffaloes than in cows. This result in buffaloes resulted in a marked decrease of heat production at a lower environmental temperature. On the contrary, an increment of heat production was higher in buffaloes than in cows. As a result, the former might exceed the latter in a balance of heat production. These results have shown that the fluctuation of rectal temperature in buffaloes is a means of conservation of heat production, though it is not always associated with a decrease in the maximum value in rectal temperature. These results were caused by a high heat conductivity of their bodies and a low heat production. The feature of buffaloes may contribute towards heat dissipation during wallowing which increase sensible heat loss by water and mud. Therefore it is highly possible that the heat dissipation system is adaptable to a hot-humid climate and is supporting buffaloes in animal production in this area. The paper is awarded 5th (2000) AJAS Purina Outstanding Research and thanks to the AJAS and Purina Korea Inc.