Housing designs that optimize an animal's thermal environment

Abstract

Modern animal housing systems need to provide optimum thermal conditions to maximize the animal’s genetic growth potential and performance as well as meeting an essential component of an animal welfare/well-being program. The environmental conditions include parameters such as room temperature and humidity, air speed across the animal, the indoor air quality for confinement facilities, respiration rates for animal in outside lots, plus others features like light and noise levels conducive to the animal’s comfort and well-being. Environmental control systems in animal production units also need to be integrated into the overall housing system design rather than added on at the end of the design and/or construction process. Effective management and operation of these environmental control systems is as important as the design and selection of components. Latest technologies such as solid state electronic controllers need to be used to provide more precision and reliability in the operation and control of such critical criteria as exhaust fans operation or sprinklers in an outside feed yard. However, it is still very important that the person(s) managing the control instruments and devices in the field, understand how the environmental control system works and how it can be adjusted to maximize the system’s effectiveness. The thermal requirements for various species of livestock and poultry are well documented. Mammals and birds are homeotherms, since they are able to keep a relative constant core body temperature (39 °C for food mammals and 41 °C for domestic birds, Curtis, 1983) over a wide range of environmental temperatures. Even though pigs, cattle, and chickens can survive over a wide range of environmental temperatures, we are most interested in what is commonly called the thermoneutral zone. Figure 9.1 shows the relative response of key production parameters, such as feed intake, growth rate and feed efficiency, for grow-finishing pigs (average weight of 70 kg) over a normal range of environmental temperatures (5 to 33 °C) that might be experienced. The thermoneutral (sometimes called thermal-comfort) zone is highlighted by the vertical bars on the figure and can be defined as the condition where the animal is neither cold nor heat stressed. More importantly for our discussion, this range of environmental temperatures is where the critical production parameters of growth (average daily gain, ADG) and feed efficiency ( FE) are optimum. Thus, this is the target or ‘sweet spot’ temperatures for any environmental control system in a livestock building. The environmental temperature range for the thermoneutral zone will vary by animal species with a relatively narrow range (2 or 3 °C) for small animals (birds) and a much wider range (from 5 to 10 °C) for larger animals such as finishing pigs or cattle. The low and high end of this range is called the lower (LCT) and upper critical temperatures (UCT) respectively. Depending on the season and where the housing system is located in the world, the target temperature or goal of