EFFECTS OF AMBIENT TEMPERATURE AND HUMIDITY ON THE URINEOUTPUT AND PLASMA OSMOLALITY IN GOATS

Abstract

Urine output (volume and osmolality), water intake, respiratory rate, plasma

osmolality and packed cell volume (PCV) of six Australian feral does during 4 week

exposure to hot-humid, hot-dry and cool-humid conditions were determined and

compared with those of 3 weeks exposure to control conditions conducted prior to each

of the treatment conditions. Compared to that in control condition, urine volume

(ml/W0.82kg/d) was higher in hot-humid, hot-dry and cool-humid conditions. However,

as the proportion of water intake, the urine volume in hot-dry condition was reduced to

the lowest level, whereas water intake was increased to the highest level. This is an

indication of increasing water requirements for dissipating the excessive heat through

water loss by evaporation, as indicated by a faster respiration rate in the hot condition.

Compared to that in hot-dry condition, urine volume in hot-humid condition was

higher, whereas water intake was lower. A higher urine volume in cool-humid

condition was concomitant with a lower water intake compared with that in hot-humid

condition. In all treatment conditions, urine osmolality were markedly lower than in the

control condition. Plasma osmolality and PCV were maintained relatively constant,

although there were possibilities of increasing plasma volume during hot conditions.

Water intake related positively with ambient temperature but negatively with ambient

humidity. On the other hands, urine volume related negatively with temperature but

positively with humidity. The results indicate that prolonged changes in ambient

temperature and humidity were particularly affecting the alterations in urine output

(volume, osmolality), whereas plasma osmolality was relatively constant.