by Harry Huffman, P.Eng, OMAFRA
There are a number of suitable housing environments available for raising calves however, there is no housing environment that is vastly superior to another. No matter which housing system is chosen the main elements for raising healthy calves includes:
- providing plenty of fresh air
- maintaining an acceptable temperature while minimizing temperature fluctuations
- keeping various air pollutants such as ammonia, carbon dioxide and airborne pathogens to a minimum
- and maintaining a clean, dry environment.
These conditions are not always easy to achieve due to changing weather and winds, barn style and location, and operator management. With each calf respiring approximately one liter of water vapour into the room environment every day it also becomes difficult to maintain a dry environment. This moisture must be removed with the ventilated exhaust air and replaced with fresh air while minimizing the potential to cause drafts around the calves.
It is important to find a ventilation system that is compatible with the chosen building design and its specific features such as leakiness, beam and post obstructions, insulation, etc. All this must be achieved while keeping in mind that the goal of every ventilation system is to maintain a dry, draft free environment for the calves regardless of whether the barn is operating as a cold barn or a warm barn.
Cold Calf Housing
If a cold calf facility is desired (<8°C), there are many housing styles to choose from depending on your budget, convenience factors, number of calves to be housed and the degree of environmental control desired. However, when considering ventilation, natural ventilation is the only acceptable type to consider. Fans (mechanical ventilation) will only enhance floor drafts and can potentially lead to sick calves. The one exception to this would be in the movement of extra air in hot weather to relieve heat stress.
Natural ventilation utilizes two physical forces to perform its ventilating function. Firstly, it relies on the wind to move large quantities of air around and through the building. This movement of air around and over the building will assist in drawing air out through the peak or chimneys if they are present. Exhausted air is replaced at the sidewalls and any other openings. This incoming air is generally a few degrees cooler and will fall to the floor potentially leading to drafts. The second physical force of ventilation is the buoyancy principle of warm air being lighter than cold air. Providing the calves are able to raise the barn temperature even a few degrees above the outside temperature then this warmer air will rise carrying moisture and other contaminants to an exit ridge or chimney opening.
These simple structures whether home made or commercially bought have proven to be very successful and economical housing units for a small number of starter calves. The calves can be kept dry and draft free if properly located and adequately bedded. A protected location out of the wind, with access to winter sun and summer shade is ideal. Often times these requirements mean moving the hutches seasonally, but this helps break any disease cycle which may persist in the same location. Food intake must also be properly adjusted to compensate for the living in a colder environment. Of course the biggest draw back of using calf hutches is the inconvenience of looking after the calves regardless of the weather.
Calf Hutches in an Uninsulated Shed
This arrangement can improve the working conditions for the operator, but the building must be adequately equipped with sidewall air inlet vent panels and a ridge exhaust to provide natural ventilation without drafts and damp air. The hutch is still very important in this type of building since the calves cannot generate enough heat to raise the barn temperature above that of the outside temperature. Thus, the hutch creates a microclimate for the calf, while wind forces alone ventilate the overall building.
Individual and/or Group Pens in a Fully Insulated Shed
With this type of facility calves have the capacity to raise the barn temperature a few degrees such that both buoyancy and wind forces can ventilate the barn naturally. Success will hinge on the manager’s ability to adequately monitor and control the ventilation openings to maintain a constant environment. Some producers have automated the sidewall vent panels to open and close according to temperature of the barn.
Cold Gable-Style Barn
While it is possible to operate a building without very much insulation, at least R 5 insulation will prevent condensation on all the metal surfaces. This will greatly assist in actually getting this moisture completely out of the building. Some barn insulation helps the calves maintain the inside temperature a few degrees higher than outside such that the thermal buoyancy is not dissipated prior to the air exiting the peak. If the barn is too big for the number of calves housed, even if well insulated, there may not be sufficient thermal buoyancy to make this aspect of the ventilation work. Many of these barns will use chimneys with a control damper located near the peak to assist in keeping the barn including the chimney a little warmer and thus maintain a thermal buoyancy. To limit drafts, it is recommended that the fresh incoming air enter at the top of the sidewall, farthest from the calves. Additionally, having some solid pen partitions will limit across the floor drafts. Temporary walls using straw or hay bales is a very effective management strategy for cold weather. Of course, warm weather ventilation is achieved by fully opening the side wall panels and allowing wind ventilation to occur through the building.
Chimney Openings = 0.5% of the floor area; Sidewall Openings = 4 to 5% of the floor area on each side.
Nebraska Style Modified Open Front Barn
These barns have been tried for calves, but due to their extra floor area and large air volume in relation to the number of calves housed, good ventilation and healthy calves has been difficult. These barns have been excellent for older calves, heifers and dry cow housing due to the extra animal heat available to assist thermal buoyancy.
Tarp-Covered Arch Frame Buildings
This type of building adds a new dimension to good ventilation. Many of these structures only have openings at the two gable ends and rely on wind movement and small air pressure differences to exhaust air out one end and inlet fresh air at the other. These building are extremely vulnerable to floor drafts from end to end. During cold weather air leaks along the bottom of doorways need to be sealed and air should be vented near the top of the gable walls. It is also important to keep these structures fully stocked in cold weather to have any thermal buoyancy assisting the ventilation. Several developments have assisted this style of building:
Some of these buildings are now available with an open ridge to allow warmer, moist air to escape all along the peak. This feature will be advantageous for buildings housing older calves and heifers where there is more thermal buoyancy at work.
The introduction of shade cloth as a covering for the gable ends of these structures has been a major stride in ventilation improvement. This shade cloth is 20% to 40% porous and allows the air to move through the building’s air space at a gentler speed over a larger surface area and reduces drafts considerably. Some producers are doubling up the shade cloth for the bottom 4 to 6 feet to further limit the air flow at calf level.
Plastic-Covered Greenhouse Structures
These greenhouses are covered with a single or double layer of plastic and the gable ends are equipped with shade cloth providing a very acceptable calf housing structure. They are bright and airy but need some special attention during warmer weather to prevent them from becoming like a hot house. To overcome this, the bottom of the sidewalls are rolled up or completely removed to allow a cross flow of air and the top of the structure is covered with shade cloth to reduce solar heat gain.