In our very hot and humid climate here in Sarawak, we must have found that the heat and humidity can and will cause a reduction in the amount of food our Goats intake.
We must realize that a great deal of heat is produced in the process of digestation, which must be lost if the Goat is not going to overheat. Most of this heat is going to be lost through ‘sweating’ which become much less effective in humid environments. Goats rely on evaporative cooling from the respiratory tract. Consequently, high humidity associated with high temperatures is stressful to the animals as it interferes with their ability to regulate body temperature. If indoor temperatures rise above 30°C (85°F), a comfortable environment can be maintained by keeping the relative air humidity below 60%.
Above 30°C (85°F) your Goats will start to experience mild heat stress, more so when the humidity turns up the heat index. As heat and humidity climb, Goats will start to develop a serious problem with thermal stress. Goats get 8 times more relief from panting than sweating so rapid breathing is their primary form of cooling themselves.
During the hotter parts of the day you will notice your Goats will stop eating. You may also notice them lying on their sides flat out. They have stopped not because they have a full tummy but because they are having difficulty in keeping their body temperatures down to a tolerable level if their rumens are very actively digesting food and producing heat.
How we tackle this is to allow our Goats to go out into the paddocks in the early morning for their foraging and come back in the mid-afternoon where they are fed at around 3pm. They might be let out again for more foraging before being let back in during the late evening.
How to read the chart – Find the temperature on top, then move to the left until you find the column for the approximate relative humidity. That number will be the temperature that it will “feel” like. For example, a temperature of 90°F and relative humidity of 50% will “feel” like 95°. Add up to 15° if in the direct sun.
Humidity can be measured indirectly with dry and wet-bulb thermometers. The dry-bulb is an ordinary mercury-in-glass thermometer and measures the air temperature. The bulb of the wet-bulb thermometer is covered by a muslin bag which is kept moist. It gives a lower reading than the dry-bulb because of the cooling effect of water evaporating from the muslin bag.
The two thermometers may be placed in a Stevenson screen, or whirled together in a sling (sling psychrometer), or ventilated by drawing air past them with an electric fan (aspirating psychrometer). The difference between the wet and dry-bulb readings is a good indication of the efficiency of evaporative-type coolers and the wet-bulb reading is a reasonable indication of Goat comfort.