For aviculturists working with indoor or even partially enclosed breeding aviaries ventilation systems must be incorporated into room design. The desire to conserve heating costs must be reconciled with the requirement for clean and healthy indoor air. The basics of good ventilation are an abundant supply of fresh air, adequate circulation of that air and the elimination of temperature fluctuations. Good ventilation and a well designed confinement building, combined with a good sound management program, results in better control of odour, humidity and pathogens.
The object of ventilation is to provide a healthy environment for birds. Inadequate ventilation can lead to increased concentrations of ammonia and pathogens and decreased oxygen, and extremes in temperatures.
The five principles of ventilation apply to all types of housing, both open and closed:
UNIQUE RESPIRATION AND DISEASES
The unique and highly efficient avian respiratory system functions in maintenance of blood pH, proper blood oxygen tension and regulation of body temperature. Many respiratory diseases are triggered due to initial irritation and inflammation of the respiratory mucosae and subsequent invasion by microorganisms. These microorganisms are found at higher levels in bird rooms with poor ventilation systems.
DESIGN AND CONTROLS
Housing design is very important in controlling the direct environment of birds. Insulation in the ceilings and walls helps to keep the house warmer in cold weather by conserving heat and cooler in summer.
The elements of a good ventilation system are adequate insulation, sufficient fan capacity, proper air inlets and ducts. Ventilation systems may use gravity convection to move air but this is often not enough, thus the need for a forced air system. Forced air systems utilize fans and may provide either positive, neutral or negative pressure within a room. Negative pressure should be used in quarantine/isolation rooms so that no air flows from sick birds to healthy ones.
Positive pressure ventilation typically employs a fan mounted at the end of the house that pushes air into a duct along the ceiling spanning the inside length of the house. Stale air should be allowed out near the floor so that a laminar flow from top to bottom is created.
Negative pressure systems use fans mounted on the sides of the building that blow air out of the room. Fresh air enters through openings controlled by baffles. A duct or multiple openings should be used to direct the incoming air to prevent drafts which may be created around a single intake opening. A central ridge duct inlet along the top of an enclosure with fan extraction through side walls is an efficient way to create a draft free laminar flow of fresh air.
Placing resistance on fans (such as ducts, elbows, diffusers) will reduce the airflow. The cubic feet per minute (cfm) i.e. quantity of air flow labelled on a fan is therefore higher than that when installed.
If systems were better designed and properly maintained, less disease outbreaks would occur and chronic health problems could be reduced. Drafts and dead air spaces should be eliminated. Strong cross winds directly on weak fans or inlets will affect their performance. Fans should be located to minimize this.
Maintenance of a healthful environment includes keeping the ambient air temperature within the thermo-neutral zone of the species and age of the birds. The air temperature entering the room should be controlled 24 hours a day through the provision of heating and cooling devices, adjusting for daily fluctuations.
Heat stress depresses the appetite and fertility of most livestock. Although most exotic birds come form tropical areas, there are cool areas for them to roost and nest in within these habitats. Under the canopy of rainforests its cool and damp.
Foggers or green house misters installed above the flights are an excellent way to decrease temperature and increase humidity in hot and dry climates. Watering the roof can also be used in reducing the roof temperature. Therefore, when water is freely available in hot and dry areas, consideration should be given to the installation of sprinklers over the roof.
FILTERS AND PADS
Recirculation of filtered air within the aviary should only be done if complete filtration of the air is done and can be maintained.
Most air-borne viruses, molds and bacteria are between 0.01 to 50 microns in size, they thus need High Efficiency Particulate Air (HEPA) filtration. Washable foam and carbon prefilters only remove odors and larger particles such as feathers, dust and dried feces.
Some species of birds, such as cockatoos, produce powder down which will quickly clog up prefilters and fine particulate filters. Total recirculation without some fresh air input may result in a lack of oxygen for the birds.
Pad cooling systems are efficient in cooling the air in hot regions by using the cooling effect of evaporation of the water which is passed over them. However they become clogged with the mineral contents of the water left over after evaporation thus must be cleaned periodically.
Screened exhaust fans openings quickly become clogged with dust, feathers and other particulate matter, greatly decreasing their efficiency. Also check fan speeds and clean dust from the blades and guards. Keep weeds and grasses cut low around fan openings.
Air-to-air exchangers are designed to extract heat from the exhaust air of buildings. Warm moist exhaust air heats radiator-like modules which, in turn, transfers it's heat to the fresh incoming air. They should maintain neutral pressure ventilation when balanced. The energy savings, versus if fresh air had to be completely heated, covers the cost of exchange units usually within a few years. These units are highly recommended for indoor northern aviaries and cost less than a new pair of parrots. Most hardware and home appliance stores carry models costing between $500 - $800.
Minimum acceptable levels of air exchange per hour is difficult to state because of different densities of birds. Some building codes for human occupancy range from as low as one half an air change per hour (ACH) up to 12 per hour. Based on our experience at HARI, with about one pair of medium sized birds per 48 square feet of floor area, three ACH during the winter and 12 ACH during the summer seems to keep the air in the bird rooms clean and fresh.
VENTILATION STANDARDS FOR QUARANTINE HOLDING AREAS
While APHIS regulations require that ventilation capacity within quarantine facilities be sufficient to protect the health of quarantined birds, there are no quantifiable methods in use to determine whether that requirement is met. The Cooperative Working Group on Bird Trade Recommends that APHIS promulgate regulations that: establish and identify methods to enforce quantifiable ventilation standards; and require screens, fans and other ventilation surfaces or devices to be thoroughly cleaned of particulate matter upon completion of quarantine; examine potential methods of increasing ventilation using current quarantine design e.g. increasing air exchange through existing openings such as quarantine entrances.
Anonymous (1990). Findings and Recommendations of the Cooperative Working Group on Bird Trade (USA) pp 47.
Qureshi, A. A. (1990). Effective Ventilation Can Reduce Medication. Poultry, Vol. 6:2 pp 16-17.
McDermott, H.J. (1985) Ventilation for Contaminant Control. Butterworth Pub. Stoneham, MA pp 402.
Sainsbury, D and Sainsbury,P (1988). Livestock Health and Housing. Baillere Tindall, London pp 319.
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