Effect of Environment on Respiratory Disease

The veterinarian should not be content with examining only the goat with respiratory disease. The nutrition and environ­ment should also be analyzed to determine if they are con­tributing to the pathogenesis of disease.

Temperature

At environmental temperatures above or below the opti­mal limits given in Table 9.3, the goat has to expend energy specifically to maintain its normal body temperature. As a consequence, production (milk or growth) is adversely

Table 9.3 Optimal housing for goats in temperate climates.

Source: Toussaint 1984 / Institut National de la Recherche Agronomique.

affected. In a hot environment, the goat must decrease its heat production (eat less) while losing more heat through evaporation and radiation from lungs and skin. Under cold conditions, the goat must use more energy from feed or body reserves. It will also have increased levels of circulating glucocorticoids. Age and production level both affect the critical temperatures. For instance, the min­imum temperature for kids is higher than for adults (Constantinou 1987).

Ventilation

Ventilation affects the purity of the air that the goats breathe. Heat, moisture, and carbon dioxide from the lungs need to be dissipated. Decomposition of feces and urine produces ammonia, hydrogen sulfide, methane gas, and other malodorous substances. A build-up of these chemi­cals can lead to irritation of the eyes and respiratory tract. Heaters and motorized equipment operating within the barn add to air pollution. Suspensions of dust from feeds and dirt carry with them numerous pathogens and sapro­phytic organisms. Coughing and sneezing serve to excrete many germs into the air in droplet nuclei (Ojo 1987), while dust helps to keep them airborne. Warm and humid condi­tions favor the survival of microorganisms in the air.

Animal Density

Overcrowding increases both the temperature and humid­ity in the barn because more goats generate heat and moisture into the atmosphere. Manure can also signifi­cantly increase the temperature. The surface area allotted per goat should be a minimum of 0.5 m² per stanchioned animal and 1.5 m² per adult in a free stall setting (Toussaint 1984). The minimum per unweaned kid is 0.3 m². The minimum feed trough length recommended per goat is 0.4 m. With the inclusion of feed alleys, the typi­cal area per goat in the barn is 2-2.4 m². The height from the bedding to the ceiling then determines the volume per goat. If the ceiling is too low, temperature and humidity increase. If the air space is too great, the barn may be too cold in the winter.

Even when goats are not housed in buildings, crowding them closely together will contribute to the spread of res­piratory pathogens as well as to the stress placed on the animals. Thus gathering into tight groups for purposes of protection from predators, transport, or management prac­tices such as shearing, foot trimming, or vaccinating can predispose to an outbreak of respiratory disease.

Building Construction

The building where goats are housed should serve several functions. First, it should shelter the animals from intem­perate weather while providing a suitable microclimate for the goats. The comfort of the goat rather than of the owner is paramount. Second, the building should be constructed so that the owner can group animals as necessary and effi­ciently perform all the tasks required for management of the herd. The building and its equipment must not be so expensive that the owner cannot pay the mortgage.

The barn should be situated where natural ventilation and drainage are good (top of a rise, not the bottom of a slope). In cold climates, exercise lots should have exposure to winter sun and a protective wall relative to prevailing winter winds. The barn should be situated away from wells and streams to avoid contamination of groundwater.

Proper construction of the barn is required to obtain the desired ventilation rate, whether natural or mechanical ventilation is used (Constantinou 1987; Collins 1990). In particular, the placement and size of air inlets and fans are very important. The assistance of an expert in this field should be sought when designing a barn or attempting to correct a preexisting problem (Bates and Anderson 1979). Fans and air intakes must also be cleaned regularly to ensure continuing function of the ventilation system. Plastic netting may be used to temper prevailing winds.

In cold climates, and in kid-raising facilities, insulation of the building avoids the stresses associated with large daily temperature fluctuations. While insulation prevents water condensation on the ceiling, it requires more ventila­tion to remove moisture. A very serious error is lining the barn with plastic sheeting with the thought of keeping the goats comfortably warm. High humidity and dripping of condensed water onto the goats predispose them to pneu­monia. Leaky waterers also increase humidity, as does inadequate provision of new bedding.

A last way in which building construction can help to limit respiratory disease is in the provision of appropriate isolation facilities. Sick animals should be removed from the main pen, and purchased or boarded animals should be kept isolated from the herd for a minimum of two weeks. If attendance at shows is part of the operation of the herd, the traveling goats should be kept isolated from the stay-at- home animals for an equal time period, though this may in effect mean running two herds during the show season.