Management and control of the poultry house environment

The environment provided to poultry flocks has a great bearing on flock performance and profitability. The basic environment consists of feed, lighting, air (temperature, humidity, pathogen concentration and ammonia), water, and litter quality. Table 1 gives general relationships between various environmental factors and performance.

Evolution of the poultry house environment

Control and monitoring of the poultry house environment has evolved through two different phases involving poultry rearing: 1) the phase whereby mechanical and electrical devices come into use and 2) the phase where computers monitor and direct the use of mechanical devices. Every poultry unit likely has components of all two phases for different environmental factors to be controlled.

The role of microenvironment

 As poultry units have come to rely upon computer controlled and monitored environments, the role of microenvironments, or significant differences in environmental conditions within the same house, have become more important. A major advantage of computer-controlled systems is the possibility of continually adjusting the devices which can alter the environment, based on numerous sensors placed throughout the house. This is especially evident in the larger environmental controlled houses being built today. This fact and the decreasing pool of high quality labour in some parts of the world have made an increase in computer control a necessity.

The level of automation and computerization is based on several factors: climate and type of housing; labour (quality and availability); potential performance due to better environment; risk and potential monetary loss and size of operation the owner oversees.

In the last few years, ventilation has become an integral part of poultry rearing. Poultry farmers have recognised the importance of ventilation during winter as well as during summer:

• To improve environmental conditions and birds welfare;
• To retain bird body heat during winter;
• To reduce summer heat stress.

Today the trend is to build closed sheds with good insulation and ventilation system. In open sheds with continuous curtains or windows, ceiling fans or suspended fans are added. They are used to create indoor air circulation in winter and to remove heat and create a cooling effect in summer. There are many types of ventilation systems, so the choice will depend on outdoor climatic conditions, anti-pollution requirements, stocking density and the type of rearing.

The most popular ventilation systems include:

• Cross ventilation;
• Tunnel ventilation;
• Positive pressure ventilation.

These systems supply minimum volumes of air at low speed to recycle bird body heat and warm the air inside the shed during the winter, and to increase thermal exchange during summer.

The large diameter, low power fans are always more and more used. Such fans work at a constant number of revolutions (to reduce power consumption), at specific intervals, to satisfy bird ventilation requirements and maintain temperature set points. Thus sudden changes, which would be harmful to the birds, are avoided and power consumption is reduced.

Air inlets

The type of inlets will depend on the type of ventilation. It is important that the direction of the air jets be in harmony with overall project. Inlets are operated by an automatic control panel, so no operator is required.

The regulation panel

The automatic heating and cooling temperature set points are programmed on this panel. The control panel supplies minimum ventilation, and times fans to retain bird body heat and reduce energy consumption.

Cross ventilation

Fans are installed on one side of the shed and the air inlets on the opposite side. It is a valid system for high stock density, when a large number of fans are necessary. The air inlet is designed to supply two jets, one for winter which goes over the batteries, and the other one for summer, which goes all over the shed.

It is a very ingenious system based on the principle of a high-speed air stream near the ceiling and low speed air stream at bird level to recycle bird body heat in winter. In summer air speed is higher, creating a cooling effect.

Tunnel ventilation

This is the ideal system for broilers, layers and chicks. Fans are installed in one end wall and air inlets are installed in the opposite end wall. This system also features low air speed in winter and high air speed in summer. It is a perfect solution for areas with very cold or very warm climate. The system permits control of the minimum air quantity, so it is an ideal solution when it is necessary to heat and to recycle indoor air.

The system is equipped with jet diffusers, and fans which draw in outdoor air and recycle indoor air. With a polypropylene perforated duct which runs the length of the barn, the jet diffusers attain a uniform distribution of minimum air volumes.

The possibility to control the minimum air volume is very important to retain environmental heat and to reduce feed consumption without damaging bird welfare.

This ventilation system is easily adapted to existing barns because installation is quite simple. It may also include a central heating system with warm air generator connected to the jet diffusers, as well as a cooling system with pad cooling or high-pressure nozzles.

Positive pressure ventilation

The main feature of this system is the low air speed at bird level. Fans are installed in chimneys and air outlets are in the pit. The whole barn is involved in the ventilation pattern, which creates temperature uniformity.

Air circulates first in the bird’s area, then in the manure pit underneath with a dehydrating effect: the ventilation is created by ceiling fans.

Considering present awareness of the pollution problem positive ventilation is one of the best systems to employ, particularly when farms are close to residential areas. No fan noise is perceptible outdoors because fans are installed in openings on the shed roof. Dust and feathers stay inside the barn and dry manure is odourless.

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