As with any production system, equipment selection and facility design are critical for success. Climate, pig flow, energy costs and other considerations must be factored in.
The most common wean-to-finish (W-F) designs are similar in building and pen configuration to our standard grower-finishers. Buildings are 40 ft. wide with two rows of 10-ft.-wide pens divided by a center walkway. Ventilation is usually sidewall or pit exhaust fans for cold and moderate weather and natural ventilation for warm/hot weather.
Typically, pens hold 25 pigs with a density of 7.5 sq. ft./pig for single stocking. For the past few years, facilities have used wider rooms for buildings of 50 ft. and 60 ft.
In an effort to further reduce cost per square foot, double wide (80-120 ft.) barns have also emerged. Along with wider rooms, larger pens of 75-250 pigs are common.
Actually, the 50-ft.- to 60-ft-wide rooms really call for larger pens to avoid narrow pen widths that could increase social stresses and reduce access to feed, water and resting/ sleeping zones. Experience and feedback from producers with these wider rooms and larger pen sizes is extremely positive.
Tight Facilities The first step in remodeling or building new W-F facilities is to reduce air leaks. This helps achieve proper air exchange rates and reduces ventilation heat loss.
The second challenge caused by large air leaks is poor air distribution and mixing. If too much air enters through leaks rather than the planned air inlets, air inlet velocity can't be maintained. This results in dead zones with poorer air quality and large temperature differences within a room.
Most facilities are curtain-sided, some using insulated curtains. A few units feature insulated stud walls instead of curtains.
Regardless of building type, focus on tight construction. A good sill seal, for example, is a must between the concrete stem wall and bottom sill plate. Curtains, if used, must be installed, adjusted and maintained to close tightly. Many facilities have tremendous leakage at the bottom of the curtain. This can be fixed by sandwiching the curtain between the sill plate and wood or polyethylene strips fastened with screws 6 in. on center, maximum.
In most weather, good curtain installation and maintenance can adequately reduce leaks. With extreme cold, windy weather or leaky barns, temporary use of heavy-duty plastic stapled on the inside of the curtain walls may be needed to reduce heat loss.
One of the first W-F buildings that I helped design the summer of 1996 was 60 ft. wide with insulated sidewalls. The producer used all mechanical ventilation with sidewall exhaust fans and ceiling air inlets for cold and moderate weather and tunnel ventilation for hot weather. For heat, we installed two-stage, overhead, radiant tube heaters over the center alleyway to heat the front area of each pen.
The heaters and the entire ventilation system are controlled by a multi-stage controller that can be adjusted at the room or from a remote office computer via a modem interface. The controller keeps a historical record of heater run time by room. This run time enables the producer to project propane use based on Btu input of the heater using 93,000 Btu/gal. of propane as a guide. The producer's estimated use of heating fuel was only 1 gal./pig through the winter, much less than curtain-sided, W-F buildings.
A tight facility, top management, 60-ft.-wide building and insulated walls helped achieve low fuel usage.
Some W-F buildings have used 100% natural ventilation with chimneys and, despite my pessimism, seem to be working fine. Precise natural ventilation does require a sophisticated control system including a relative humidity sensor to maintain adequate minimum ventilation. Of course, management and sound design are also a must.
Heating System Options One of the first concerns most producers have before trying W-F is keeping the weaned pigs warm enough. Their next concern is how to do it.
The answer is to use radiant zone type heat systems. Radiant heaters emit infrared rays like the sun. They don't heat the air directly, only the objects that the infrared waves strike. Warmed objects, slats, penning or pigs warm the air.
Because most W-F buildings are more prone to heat loss (not as well insulated) than typical nursery buildings, some type of radiant zone heat source (electric or gas) is often used. The objective is to reduce heat loss by zone heating the lying area and allowing the air temperature in the rest of the room to be 10-15 degrees lower. For instance, while the lying area temperature is kept at 85-90 degrees F, it may only be 70-75 degrees F in the dunging area.
Radiant zone heating does reduce energy costs over forced air heating. It is also one of the keys to improving pig performance.
Agricultural engineer Ron MacDonald, Guelph, Ontario, and I discovered the true benefit of radiant zone heating after a field study we coordinated during the winter of 1994-95. In a Midwest nursery facility, we compared performance of a zone heat system provided by two-stage, gas, overhead, radiant tube heat to that of forced-air, gas heat. We observed whether pigs chose to sleep close to or away from the radiant zone heater. Gas use declined, but most importantly, we recorded better pig performance. Death rate, feed conversion and especially daily gain were better for the radiant zone heat system.
With traditional, forced-air systems, we heat to meet the needs of the smallest and/or least healthy pigs in the room. Consequently, many pigs are either heat stressed or uncomfortable. They compensate by eating less to lower body heat production.
For heater design, first decide how big an area needs to be covered with radiant heat. Coverage area should be equal to the smallest lying area required. Of course, this depends on the size of the pig.
Unfortunately, the coverage area of radiant heat has been influenced more by the type of radiant heat source than actual pig needs. For example, a typical radiant heat lamp hung at 32-36 in. above the floor essentially covers an area of 7-10 sq. ft. (enough for about 20 pigs at 10 lb. or 12 pigs at 20 lb.). Of course, the amount of radiant energy received by the pig directly under the lamp will be much greater than the pig lying at 1.5 ft. from the center, depending on the type and size of bulb used. This allows pigs to arrange themselves under the lamp to meet their own needs. The problem is that many systems are only using one lamp per 25 pigs when they should have at least two lamps. With good pig health, some producers can get by with one lamp by raising the temperature setting 5-10 degrees so the forced-air heater runs more.
Economics dictates you can't afford to provide electric heat for very long because electricity is much more expensive than gas (Figure 1). For example, if electricity costs 8 cents/kwh, an equivalent heating fuel cost for propane would be $1.68/gal.
Common W-F Heating Systems There are three main types of heating systems being used in most W-F systems: electric heat lamps with forced-air gas heat, gas-fired radiant brooders with forced-air gas and radiant tube heat.
To cut heating costs, radiant heat should be used at least 2-6 weeks, based on the climate and season. For electric lamps, I suggest sizing for at least 20-lb. pigs (0.84 sq. ft./pig). For gas radiant heat (tubes or brooders), I suggest sizing for a 40- to 45-lb. pig (1.5 sq. ft./pig).
The heat lamp and gas brooder systems are operated similarly. The lamps or gas brooders provide a zone heat while traditional, forced-air gas heaters maintain room temperature at 70-75 degrees F for the first 5-6 weeks (until pigs are about 40 lb.). Depending on the controller, lamps can be operated, on/off, high/low/off or variable. Lamp usage is decreased as the pigs grow and turned off when pigs are old enough to sustain growth with a room temperature of 72-75 degrees F.
With brooders, target zone temperature is gradually reduced as the pigs grow. Some brooders cycle on and off while others are variable output. When the target radiant zone temperature is the same as the target room temperature, the brooders are turned off. After the lamps or brooders are turned off, the room temperature is adjusted as you would for grow-finish.
Facilities that use overhead, radiant tube heaters usually don't need a backup source of forced-air gas heat. Unlike most brooder systems which have a separate controller, tube heaters are controlled by multi-stage ventilation controllers. Producers like tube heaters because they only have to adjust one temperature controller for all the heating and ventilation equipment. Target temperature is reduced gradually as the pigs grow as you would in a typical nursery. Sensor location for zone heating systems is critical. For tube heaters the sensor must be located close to the radiant heat zone.
Heating System Costs There are two types of costs for heating systems: the initial equipment and installation costs and the operating costs for energy use and maintenance. Figure 2 compares these costs based on data collected from research at a site in central Illinois. The facility has four, 50-ft.-wide, 1,200-head rooms with insulated curtains.
Most producers do a good job of comparing the equipment costs but struggle with the true installation cost of each system. Although the cost of heat lamps is the least equipment cost, the system has the highest installation cost. Even though we projected heat lamps to operate only three weeks per turn, they still had the highest energy cost. This is because electricity is three to five times more expensive than gas.
Our current projections show that even though the lamp system has the lowest initial cost, the gas brooder system has a 1.9-year payback and the two-stage, overhead tube heat system would have only a 1.4-year payback for this Illinois facility.
Flooring The most common flooring is pre-cast, concrete slats. Also used are wire mesh, plastic and partial solid concrete. High quality concrete slotted flooring works well. If slats are not high quality, you're better off with partial plastic flooring for fewer feet and leg injuries.
Piglets quickly learn to walk on the tops of concrete slats. During the first few days, a leg might slip down into a slot, but with a wide enough opening the pig can pull his leg out without any problem. Slats should have no more than a 5-in. top; a 1-in. slot is preferred. Larger tops will result in messy pens. Slot edges should be even and smooth without rough protrusions. There is a wide variation in quality of concrete slats but many people can't spot the differences until it is too late.
Manure Handling Manure handling systems are the same as used in grow-finish. Most systems are either pull-plug, recharge pits with outside storage or below building deep pits. Manure volume varies with watering system and management but is generally about 75% of a grow-finish facility. This means that an 8-ft.-deep pit should provide one year of storage.
Remodeling Several clients are remodeling facilities to W-F. This is fairly straightforward for grow-finish buildings but complicated for other types of facilities. Evaluate each barn individually.
Even in a finisher there are many changes. Penning will likely need to be modified so pigs don't get trapped with wide bar spacing. Feeders and waterers must provide access for smaller pigs. Heating and ventilation are the largest changes. The building must be tight enough to provide the ventilation rate for small pigs. Smaller, minimum ventilation fans are needed. Some type of gas radiant heat should be added.
Large Groups Some producers have asked about special environmental challenges using big pens/large groups. There may be few if properly designed.
Ian Taylor, Animal Environment Specialists, Bloomingdale, IL, believes that with the hog industry's stocking densities and heavier finish weights, large group pens offer production advantages. He stresses the need for multiple feed and water stations within large pens to assure proper access and intake.
Also, the larger pen widths allow increased pig access to the radiant heat zone and greater choice of environment. These can be real shortcomings in traditional small group, narrow pen type buildings, particularly if double stocking is contemplated. Taylor suggests this increased flexibility expands the practical options available when remodeling or considering larger, more cost-effective buildings. He advises reviewing management, such as providing simple means for pig sorting. Taylor says that other management pluses are increased ease of walking through pens for inspection and the ability to re-mix recovered pigs back into the large group pens. Penning costs are certainly less. If there is a disadvantage to large pens, it is not with the facility design or equipment requirements.
Summary Economics will dictate. Improved pig performance and reduced labor are real advantages over three-site production. Facility cost is higher. We are still collecting data for the cost of heating these facilities.
Certainly, we will see more double-wide facilities as producers realize they can have tunnel-ventilated buildings for about the same cost as naturally ventilated. The only extra cost is to operate those big fans.
As we become comfortable with the concept of large pens, we will see an increasing number of 102-ft.- and 122-ft.-wide buildings. The days of the 40-ft.-wide finisher are numbered.