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Modern commercial rabbitries are generally of pole frame construction, with metal sides and roof. They are of two basic types: those with natural ventilation and those with a controlled environment. A building with natural ventilation in temperate climates may have an open side toward a direction that does not have prevailing winds. In some areas, such as Arkansas, rabbitries commonly are open-sided, with a roll-up curtain of plastic, burlap, or canvas that can be dropped down in the winter and rolled up in the summer for better ventilation (Fig. 4.1). With natural ventilation, only one tier of cages should be used, and a long, narrow building is desirable. A central alleyway with a row of cages on each side works well.

Fig. 4.1. A Louisiana rabbitry with side flaps that can be closed during inclement weather. (Courtesy of J.I. McNitt)

Ventilation of rabbitries removes moisture, gases, microorganisms, and heat. Generally, ventilation is required in the summer to remove heat and in the winter to remove moisture. An ideal environment is about 10° to 15°C with about 50 percent relative humidity. When ventilation is adequate to lower heat or moisture to desired levels, the microorganisms and gases (mainly ammonia) are usually removed adequately also.

There are several characteristics of air important in designing ventilation systems. The higher the air temperature, the greater its capacity to carry moisture as water vapor. Agricultural engineers use charts relating air temperature to water content to determine the air volume necessary in the winter to carry water vapor from the rabbits’ breathing, from their urine, and from spilled water (e.g., from leaky drinking valves) out of the building. Another property of air is that hot air rises and cold air sinks. This characteristic is used in locating the air inlets and determining their optimal size.

Natural ventilation systems use wind and animal heat to move air. Advantages of natural ventilation include low cost and freedom from effects of power failures. Disadvantages are the lack of control over air movement, inability to lower the inside temperature of the rabbitry below outside (ambient) temperature, and overventilation (drafts).

Mechanical ventilation systems are employed in environmentally controlled buildings, using fans to provide the required air flow rate. Advantages include the potential of controlling the air flow rate to required levels for removal of moisture and heat and the ability to use the system to provide heat in cold weather. Disadvantages are the high initial and operating costs and the need for back-up systems in case of power failure.

Mechanical ventilation systems are of two types: positive pressure and negative pressure. In a positive pressure system, fans blow air into the building, creating a build-up of pressure inside. The major disadvantage of this type is that the pressure drives warm, moist air into cracks in the building and into the insulation in the walls and attic. In the winter this may result in excess condensation. Negative pressure systems are those in which the fans blow air out of the building, resulting in the inside air pressure being lower than the outside or atmospheric pressure. Negative pressure systems are more commonly used than the positive pressure type.

Movement of air in mechanically ventilated buildings is controlled by the placement and size of the air inlets. An inlet controls the direction, path, and distribution of fresh air into the rabbitry. In the summer, a lot of turbulence and air volume are needed for cooling purposes. In the winter, less air movement is required for removal of heat. Many rabbitries have insufficient ventilation in the winter, resulting in severe build-up of ammonia. Often this is followed by a high incidence of snuffles and pneumonia in the spring. Ammonia causes severe damage to the cells in the nasal passages, allowing Pasteurella bacteria to colonize. High humidity increases the problem, because ammonia dissolves in the water molecules in the air. Thus, high humidity means high ammonia. Some ventilation systems use ducts to carry fresh air from outside the rabbi-try directly to each cage.

Outlets in mechanical systems should be located on the walls so that air does not have to move more than 12m to get to a fan. Outlets should not be located so they blow into the prevailing wind. In a naturally ventilated building, the air outlets should be at the ridge (highest point of the building) to draw moist, warm air out of the rabbitry even if there is no wind (Fig. 4.2).

Fig. 4.2. Placement of winter and summer air inlets and outlets for a mechanically ventilated rabbit building (top) and for naturally ventilated buildings (bottom). (Courtesy of James A. Moore)

The economics of commercial meat rabbit production generally does not warrant the construction of environmentally controlled buildings. The returns generated from sale of meat rabbits may be insufficient to pay the interest on borrowed capital for building construction, to say nothing of utility bills for air conditioning. Therefore, it is recommended that naturally ventilated buildings be used.

Evaporative cooling systems may be used in hot, dry climates. This type of cooling uses cold water running through mats or coils. Air is drawn through these and cooled. A properly installed sprinkling system on the roof of an enclosed building will help reduce the high temperatures and, when thermostatically controlled, will be a safeguard when sudden weather changes occur. The thermostat should be set so the sprinkler will be turned on when the temperature in the rabbitry reaches about 30°C. Ideally the volume of water will be just that which will evaporate so there is little, if any, dripping from the eaves. It is the heat used to evaporate the water that produces the cooling, not the cool water flowing over the roof. This system is less effective with roofs that are properly insulated.

In many areas, insulation of the rabbitry is desirable to control environmental temperature. This is important in both hot and cold areas. In hot climates, an insulated building is necessary to complement the action of cooling systems and to minimize radiation of heat from the roof into the rabbitry. Both the walls and the ceiling of an environmentally controlled building should be insulated. With an open building, insulation of the ceiling will aid in control of high temperatures by reducing radiation from the roof into the rabbitry.

Evaporative systems do not work in areas with high humidity. An alternative that might be used in such areas is bringing in cooled air through tubes or pipes buried in the ground. The outside air is drawn through these tubes and cooled to the surrounding soil temperature (about 50°F, depending on the depth). The cooling will result in condensation of the moisture in the air, so it is necessary to slope the pipes to a sump and install a sump pump to remove the moisture.

A solid concrete floor may not be the best type to use in a rabbitry. Concrete floors lead to excessive humidity and ammonia levels, as liquid wastes cannot be readily removed. If solid concrete floors are used, provision must be made for rapid removal of solid and liquid wastes. A better system is to use pits beneath the cages, with concrete alleyways. Concrete alleyways 1 m in width between rows of hanging cages are desirable. Beneath the cages, a porous pit of layers of gravel and sand, with a drainage tile to remove liquids, is a good system. Manure is allowed to accumulate and may be removed semi-annually, quarterly, or as required. As long as the sand and gravel layers remain porous, the urine doesn’t accumulate, and the humidity of the building will not increase. The pits may be cleaned manually or with scraper devices. Gypsum (magnesium sulfate) spread on the sand immediately after cleaning will help keep the soil porous. This works even better if the gypsum is sprinkled with water after it is applied.

Various devices to automatically remove manure have been developed. They include scrapers on a cable, tractor-driven scrapers, and flushing water systems. Most of them share a common characteristic: they generally don’t work very well! Many automatic scraping systems can be seen stacked up outside rabbitries, because they weren’t satisfactory. Rabbitries with these systems usually are characterized by high humidity, a strong odor of ammonia, and many sneezing rabbits with snuffles.

It is desirable that a commercial rabbitry be equipped with lights to provide extra hours of light during the late fall and the winter. This has been shown to increase reproductive performance during this period when a decline in reproductive efficiency is often seen, presumably a result of the shortening days signaling the reproductive system that winter is approaching. The extra lighting should be used to prevent the hours of light from declining. Sixteen hours of light and eight hours of darkness are commonly used in commercial rabbitries. There is recent evidence that extra light needs to be provided in the morning as well as the evening. There is no evidence that fluorescent lighting provides better results than incandescent, although the former is less expensive to operate. The lights should be controlled by a timer like those used in poultry houses. Electrical outlets for other equipment, such as fans, should not be wired through the timer.

A good policy in a commercial rabbitry is to restrict visitors. Other rabbit raisers may bring diseases with them when they visit your rabbitry. Strangers cause stress to rabbits. A compromise policy is to install a viewing window at one end of the building. Visitors can look inside, but disease organisms and noise are kept out.

A commercial rabbitry should have an office area for recordkeeping, etc. It should be equipped with office supplies, including a calculator. A large rabbitry will find a personal computer a good investment to enhance recordkeeping and economic analysis and to produce daily chore sheets. Other components of the rabbitry include bulk feed tanks and a feed storage room. If the volume of feed used is very substantial, bulk tanks are advisable. Bagged feed is more expensive than bulk, and with increasing costs of labor and materials, the relative difference between the two is likely to continue to rise. A screen may be installed between the bulk bin and the feed cart to remove fines from the feed, if necessary. There is little difference in the amounts of fines between bulk and bagged feed of the same formula. Bulk feed may also be delivered in 800 kg nylon bulk feed sacks. They are filled from the top at the feed mill and delivered on pallets. They are removed from the truck with a fork lift or pallet jack. The rabbit raiser empties a sack by dipping from the top with a bucket or by opening a funnel on the bottom. With this system, no expensive bulk tanks are required and, because of reduced condensation, caked feed is seldom seen.

Under certain circumstances, radically different approaches to the housing of rabbits may have merit. For example, it is possible to construct a rabbitry underground in certain locations. The advantages are that control of temperature in a range desirable for rabbit production may be more feasible than with above-ground rabbitries in some climates.

In hot, arid areas raising rabbits in combination indoor/outdoor units has proven effective (Fig. 4.3). The indoor units are constructed of concrete and are connected by a large tube or directly to an outside cage area constructed of wire with slatted floors. In hot areas, the rabbits stay inside during the day and come out into the cages at night to eat. The rabbits are trained to defecate and urinate in the outdoor cages making the units easy to keep clean. Plants can be grown in the areas over the tubes which helps keep the units cool. They also have application in tropical countries, where they can be constructed of clay or other local building materials.

Fig. 4.3. A combination indoor/outdoor rabbit unit with the indoor part constructed of concrete; the outdoor unit is constructed of wire with slatted floors. (Courtesy of consortium “Green Rabbit Leprino of Viterbo,” Italy)

Other innovations include using a flushing manure removal system, with solid:liquid separation and fermentation of the solids in a methane generator. Some rabbit raisers have combined their waste disposal systems with aquaculture (fish ponds) or greenhouse irrigation. Rabbits have been kept in greenhouses, with their body heat contributing to the heating of the greenhouses. For the ingenious person there are many possibilities for using unique housing systems, particularly if only a few rabbits are to be raised.