While grow-finish and sow gestation facilities have undergone tremendous change in the past 20 years, these changes pale in comparison to those made in nursery buildings.
In the past two decades, the industry has "discovered" decks, both single and multi-tiered, woven wire flooring, plastic flooring, small-group housing, large-group housing, zone heating, room heating and wean-to-finish barns.
At the time, all these innovations were thought to be the best available technology to meet the unique housing needs of the newly weaned pig.
As these new discoveries were applied, weaning ages were declining. Late '70s nurseries were sized for 4- to 6-week-old pigs. Today nurseries are designed for 2- to 3-week-old pigs.
Pigs used to leave the nursery at 40-45 lb.; now weights are more than 60 lb.
All these changes reinforce the adaptability of the weaned pig and its ability to perform well, provided basic food and shelter needs are met.
Pig Flow Standard All-in, all-out (AIAO) has become the management standard for nurseries and grow-finish facilities. Any facility design that fails to plan for AIAO pig flow severely compromises long-term health in a production system.
AIAO by site remains the ideal. But for many producers, labor and siting issues dictate multi-age facilities at one site. The expense of multiple buildings versus a single building with multiple rooms has meant AIAO is often practiced by depopulating rooms within a facility, a less desirable practice than depopulating facilities within a site.
Pig flow also dictates pigs/room/ facility/site. Pig age shouldn't vary more than two weeks in room; under seven days range is ideal.
Pig flow and labor are key issues in the decision to build wean-to-finish versus nursery and grow-finish facilities.
Nurseries have a lower cost/pig space and are utilized very intensively compared to wean-to-finish facilities in which pig density increases the cost/pig space. This cost is partially offset by the lack of downtime associated with nursery pig movement and facility cleanup in wean-to-finish facilities.
This savings of downtime produces market weights 5 lb. heavier than conventional nurseries.
In some systems with labor concerns, the need to go to AIAO by site can only be met with wean-to-finish facilities.
Disadvantages to wean-to-finish must be weighed. Besides differences in initial investment, managing a facility as a nursery for two to four weeks and a finisher for 22 weeks is a labor challenge that must be addressed.
All these factors explain why many producers are seriously examining wean-to-finish as an option to conventional nurseries.
Stocking Density Facility size is dictated by stocking density (number of pigs/pen and space/ pig).
Performance of large pen wean-to-finish units and large pen finisher facilities (100 pigs/pen) appears equal to pigs housed 20-25 pigs/pen.
Space/pig is reduced in large pen facilities since the amount of space required for movement, dunging and eating is reduced on a per-head basis. This results in less total space/pig or more pigs/given area. The data suggests caution in adopting large pen nursery facilities until more is learned about feeder and drinker placement.
Labor is also an issue in large pen facilities. Every pen must be walked daily, and pig piles must be disrupted for observation. In small pen facilities, pig observation often can be accomplished from the aisle.
Individual pig treatment is more difficult in large pens; therefore, mass water medication is often used.
Best pig performance may not translate into the most profitable performance/pig space. A range of space allocations is given in Table 1. Note that the table includes a minimum pen width, assuming fence-line feeders, which allows pigs to stand undisrupted at a feeder. Nursery pens should be wider if circular feeders are used in the center of the pen.
Preliminary data from the University of Nebraska suggests that when nursery pigs are mixed during the move to the finisher, crowding effects are most severe if the pigs were not crowded in the nursery. Other data suggests when pigs are not mixed during the move to the finisher, crowding nursery pigs has little impact on grow-finish performance.
Flooring The move to fully slotted, plastic and metal nursery flooring in the '70s and '80s kept weaned pigs dry, separated from manure and reduced enteric problems.
Wean-to-finish housing, however, has meant a return to concrete slats and dirty pigs. Ten-pound pigs are housed on slats having a 5- to 7-in. width and 1-in. slot. While 1-in. gap is sufficient to prevent an increase in feet and leg disorders, these pigs are unable to work the manure through the slots until they are in the facility four to five weeks. Consequently, enteric problems have increased.
Gating Whether wean-to-finish or nursery, the gap between gate bottom and floor should be within 1.5-2 in. Gates should have vertical rod spacing of no wider than 1.5-2 in. While the use of vertical rod gating reduces the incidence of pig climbing, it is cheaper to build gates with horizontal rods; therefore, they are more prevalent. Spaces between the bottom rods should be no more than 2.0-2.5 in. up to a height of 11-12 in. off the floor.
Feeders Provide one feeding space for every two to three pigs in a nursery pen. The quality of the space is as important as the number of spaces provided. In many nurseries, the size of the feeder hole limits performance. Pigs up to 80 lb. are expected to eat from feeder spaces inadequate for their needs.
To alleviate this problem, some producers are installing wean-to-finish feeders in nursery facilities. They report increased feed intake during the latter part of the nursery phase. A wean-to-finish feeder having a 12- to 14-in.-wide feed space will easily accommodate three pigs/space the first few weeks after weaning and two pigs/space up to 50-60 lb. Thus, a four-space, wean-to-finish feeder provides the same eating opportunities as a 12-space feeder for the newly weaned pig.
Drinkers Data from the University of Nebraska suggests little difference in grow-finish pig performance between gate-mounted nipple drinkers, swinging drinkers and stainless steel bowl drinkers. Water wastage is greatest for the gate-mounted nipple drinkers and least for the bowl drinkers.
Water pressure at the nipple should be 20 psi or less so the pig can readily activate the water delivery device without excess water flow. Flow from nipple drinkers should be 1.5-2 cups/minute.
Gate-mounted nipple drinkers must be height adjustable. Provide one nipple drinker/10-15 pigs with at least two nipple drinkers/pen. Provide one cup drinker for every 15-20 pigs.
Temperature Control Temperatures in the pig zone should be maintained at 82-85ø F the first week after weaning, assuming minimal drafts (<0.5 mph or 44 ft./minute [fpm]) and dry pigs. Once the pigs are eating aggressively, the temperature should be reduced 2-4ø F/week. Control systems with temperature curve settings are often set to decrease the temperature 0.5ø F/day beginning one week after weaning.
Research suggests once weaned pigs are eating aggressively, they prefer a reduced nighttime temperature. In experiments in which the nighttime temperature was reduced 10ø F from the daytime setting one week after weaning for 12 or 16 hours, pigs increased the amount of feed eaten and grew faster with no difference in feed conversion efficiency.
Consider summer cooling - including wetting the pigs. As producers have expanded the range of weights typical of nurseries, they have overlooked the possibility of heat stress limiting late nursery performance.
Ventilation Ventilation systems for nurseries have to be flexible. They must provide a draft-free environment for early weaned pigs up to 80 lb. Goals are to keep relative humidity in the 50-60% range during winter ventilation and air temperature within 3-5ø F of outside temperatures during summer heat. Table 2 gives recommended ventilation rates for cold and hot weather. Because of the large span in ventilation rates from winter to summer, it is best to use small fans at first and increase fan size as you get closer to the warm rate. This is relatively easy to accomplish in large nurseries. But small nurseries have a tough time if they are to avoid a large investment in fans. Variable speed fans should be used only with properly designed controllers that account for fan performance curves.
Inlets are used to properly distribute the air. The design speed of the air is generally 800 to 1,000 fpm, but the best way to examine proper inlet adjustment is to determine where the air is falling in the pen and make adjustments to avoid drafting the pigs. Systems should be designed to avoid air speeds greater than 30 to 50 fpm on the animals during minimum ventilation conditions.
Winter inlet adjustment should provide a jet that will mix with the air in the room before falling on the pigs. This jet is best directed across the ceiling, avoiding obstructions.
Often, too many inlets are installed to provide both an adequate air jet during the winter and enough inlet capacity during summer. Inlets that can be closed during the winter should be selected. This will increase jet velocity by reducing the number of inlets. This is especially important in wean-to-finish facilities because of the wide variation in ventilation rates. Wean-to-finish facilities should be constructed as tightly as possible to make ventilation at a low rate easier.
One of the most common problems with ceiling inlet systems is the lack of adequate openings to allow air to enter the attic from the outside. If this opening is too small, the air flow rate will be restricted and distribution will also be compromised. Provide 1 sq. ft. of effective opening to the attic for each 400 cfm of ventilation air.
Heating Systems In nurseries, the easiest and cheapest heating system is an unvented, propane furnace. This provides for the temperature needs of the youngest pig, but may cause the fastest-growing pigs in the room to become heat stressed.
Options to better meet individual pig needs include zone heating systems. These may only be cost-effective in large pen situations.
Manure Management These systems have come full circle - from deep pits to shallow pits and back to deep pits again.
Air quality concerns for both pig health and worker health pushed producers to use pull-plug or some other type of shallow gutter system with outdoor manure storage. These systems reduce air quality problems because they remove manure before decomposition produces gases at the highest levels. Gases will be produced in nurseries more rapidly than in finishers because of the elevated temperatures.
Deep pits are being used again mostly due to regulatory concerns. In many states, permits for deep pits are easier to obtain or not required at all.
Drawbacks include health risks and pig discomfort if the liquid temperature is cool, creating a cold surface below the pigs.