Basic housing requirements
Pigs need a dry bed, and protection from extreme temperature and sunburn. Minimum requirements apply for space, fresh air, hygiene, access to feed and water, and accommodation. These should not predispose the pigs to illness or injury.
The importance of temperature
The temperature range required to achieve the best pig productivity is called the thermoneutral zone. Within this zone, the pig's heat production is independent of air temperature, and is, therefore, determined by its live weight and feed intake.
Critical temperatures vary according to the pigs' total weight and specific conditions in the piggery. However, if pigs spend time huddling or shivering, and eat more than usual, they are usually cold. If they avoid body contact with pen mates, eat less, foul areas of their pens that they normally keep clean (possibly lying in this and other wet areas) and pant at more than 50 breaths per minute, they are too warm.
The thermoneutral zone is bounded at its upper limit by the evaporative critical temperature (ECT) and at its lower limit by the lower critical temperature (LCT). Beyond the ECT, pigs will pant to cool their bodies through evaporation from the lungs; so the ECT can be considered the point at which spray or drip cooling is required. The upper critical temperature (UCT) is the highest tolerable temperature beyond which serious problems are likely. It is generally 6-8°C above the ECT.
If the temperature of the pig's immediate surroundings falls below the LCT, the pig must use some of its energy to maintain its body heat. Older pigs can tolerate lower temperatures for short periods without obvious ill health, but the efficiency of food conversion will suffer. The older the pig, the lower its LCT.
The most favourable temperature for newborn piglets is between 27 and 35°C. Early in its life, a piglet's ability to withstand cold is limited. If the microclimate remains below 16°C, piglet losses can occur quickly. At temperatures below 2°C, fatal chilling will occur within minutes unless warmth is provided.
Pigs can tolerate low temperatures if the area is not draughty. Danger areas are cracks in walls or near floor level; open-ended trenches, which let draught up through the slats; and uncovered heat lamps in otherwise cold buildings, which can create a draught at floor level when cold air displaces hot air. Creep boxes or covers should be used to retain warmth and reduce draughts.
A dry concrete floor can easily be warmed. Concrete does retain heat quite well, but increases the harmful effects of low temperatures when damp. Considerable heat passes from the pig into damp concrete floors even though the air temperature may be reasonable. For very young pigs, dry straw or untreated wood shavings provide excellent insulation against cold conditions.
If the temperature of the pig's immediate surroundings rises above the UCT, the pig will become severely distressed. The UCT declines as the pig's age increases. Young pigs suffer most from the cold, while older and larger animals succumb first to rising temperatures.
Temperatures over 27°C are generally considered undesirable for growers, finishers and breeders. However, if there is sufficient air movement at pig level, heat stress in dry climates can be reduced through drip or spray cooling. The resulting evaporation of water from the pig's skin can effectively reduce excessive body heat. This type of evaporation, as well as the evaporation associated with panting, becomes less effective as shed humidity rises, so having fogging sheds with water vapour is unwise.
Ventilation and insulation
Independent of environmental conditions, a minimum amount of fresh air (depending on the number and class of animals housed) must be introduced into a building to remove water vapour, carbon dioxide, ammonia, airborne dust, and bacteria and odours. However, ventilation does reduce the temperature in the shed, so it is important to insulate the roof and walls to reduce heat gain or loss by conduction, and draught-proof to reduce uncontrolled air change.
Insulation protected by a vapour barrier (if the insulation does not form its own vapour barrier) reduces condensation within the pig shed. This protects interior linings and reduces the amount of ventilation required to prevent condensation in the building.
Cold ventilating air must be directed so it creates air circulation within the shed without flowing directly on to the pigs. In a conventional, naturally ventilated shed, this usually involves using a ridge vent together with side wall vents.
Long, narrow buildings are cooler in summer and warmer in winter if the long axis runs from east to west. The pig shed should be situated to take advantage of prevailing winds for coolness in summer. Conversely, ventilation openings should be protected from prevailing winds in winter. This can be achieved by planting selected trees in a shelter belt that does not interfere with airflow required for cooling in summer. These shelter belts can enhance the appearance of the piggery and soften its visual impact. They can also affect the physical environment by effectively increasing the surrounding temperature in winter and reducing it in summer.
The eave width on the northern side of the building should be an appropriate size so the sun does not shine on the wall or into the interior of the piggery in summer, but does in winter when warmth is required.
Many diseases can affect the health of pigs. Some are caused by micro-organisms, which normally inhabit the pig's gut and, therefore, are also present in manure. In unhygienic sheds, these organisms can infect pigs via dung or airborne dust particles.
Clean, dry conditions reduce germ populations and their effect on the health and performance of pigs. Pig sheds that have effluent channels, where manure is submerged in water within the channels, can reduce dust, odour and airborne bacteria levels.
Stocking rates must not impair the welfare or performance of the animal. The 'Model Code of Practice for the Welfare of Animals - Pigs' (see Further information) provides a guide to the minimum space requirements for pigs. The code provides requirements for different weights of pigs, based on a formula, which allows the pigs to grow into the space during the weight range.
|Growing pigs; up to 10 kg||0.14||Approximately 20-30% of space allowance provides for a dunging area|
|11-20 kg||0.22||Approximately 20-30% of space allowance provides for a dunging area|
|21-40 kg||0.36||Approximately 20-30% of space allowance provides for a dunging area|
|41-60 kg||0.47||Approximately 20-30% of space allowance provides for a dunging area|
|61-80 kg||0.57||Approximately 20-30% of space allowance provides for a dunging area|
|81-100 kg||0.66||Approximately 20-30% of space allowance provides for a dunging area|
|Sows (in crates) and litters||3.2||Piglets to four weeks of age|
|Adult sows in stalls||0.6 m x 2.2 m||New stalls|
|Adult boars in stalls||0.7 m x 2.4 m||New stalls|
|Adult pigs in groups||1.4||Nil|
|Boars in individual pens||6.0||Nil|
For pigs in deep-litter housing, the code recommends at least 30 per cent more floor space per pig than the requirements listed above.
Feeding and watering facilities
Each pig requires adequate access to feed. Poor access to feed produces uneven growth and condition, impairs feed conversion efficiency and increases the proportion of downgraded pigs.
In modern grower herds, single-space or multiple-space, wet-and-dry feeders are commonly used at the rate of 10-15 pigs per feeder space. If troughs are used, the space required per pig ranges from 0.15 m per pig at eight weeks to 0.25 m for grower pigs, and then 0.3 m for finishers. Breeding stock requires 0.45 m per pig.
Clean, cool and good-quality water must be available at all times, except in situations when providing adequate quantities of whey to grower pigs is more appropriate. Weaner pigs should be supplied water via bite-type nipple drinkers or pressure plate-operated bowl drinkers, with one drinker for every 6-8 weaners. Growers and finishers should have one drinker per 10-15 pigs, though more drinkers are required in hot environments. At least two drinkers per pen is recommended. These should be placed over slats to prevent the floor areas becoming wet, and encourage pigs to use the slats for dunging and urinating. Push-type nipple drinkers waste more water than bite-types or bowl drinkers, but they allow growers and breeders to wet their skin during hot weather.
As a general guide, an entire herd will require approximately 140-160 L per sow per day (250-300 L per sow per day when flushing is included).
Partly or fully slatted floor pens are usually preferred because they are easier to keep clean. However, solid concrete floors may also be satisfactory if they are well drained.
Dry sow accommodation in a fully intensive operation needs to house about 80 per cent of breeder females at any one time, though this figure can vary between 75 and 85 per cent depending on lactation length. Additional allowance must be made for boars, replacement gilts and cull sows. Dry sows can be housed in individual stalls, or small or large groups (pens or outdoors).
Stall-housed dry sows
Stalling enables a high degree of management and can protect individual animals from aggressive sows. This is particularly important during the first few weeks of a sow's pregnancy, when aggression from other sows can cause embryos to dislodge from the uterine wall and die. Stalls are also useful for sick animals, or sows who need to lose or gain weight.
In a typical stall, the rear half of the floor is slatted. The rear laneway is 1.2 m wide, though this may be reduced to 0.6 m if the stalls have a front exit gate.
Group-housed dry sows
In response to questions about the welfare of sows in stalls, a range of group-housing options for dry sows has been developed. Major differences result from the feeding system used. The common options are:
- feeding in groups, usually using floors or troughs
- feeding in pens with open-ended full or partial stalls, usually using troughs.
Electronic sow feeder (ESF) systems, enabling individual computerised feeding at protected single-feeders, are now much more robust than earlier models. However, capital cost, and other practical ways of identifying sows and minimising aggression, are likely to limit the application of this system.
Group pens often combine a group lying area with open-ended individual stalls for feeding. Some systems use partial stalls to reduce the amount of space required per sow. The 'Model Code of Practice for the Welfare of Animals - Pigs' recommends at least 1.4 m² of floor area per group-housed sow.
Large groups in litter-based shelters
Increasingly, pregnant sows are being group-housed in litter-based shelters. These have a litter-based resting area, and open stalls on a concrete pad for sows to feed and rest in during warm weather. Such systems can work well but are usually preceded by the use of individual stalls for several weeks after mating to ensure secure uterine embryo implantation before the animals are grouped.
Farrowing and suckling sows
Pens with farrowing crates, heated creeps, and fully or partly slatted floors optimise piglet survival by providing safer and more comfortable surroundings for litters. Crates are often adjustable and some can be opened wide once the piglets are used to their pen area (i.e. where their sleeping area is located etc). Popular pen sizes are 2.1 m x 1.65 m, 2.1 m x 1.8 m, and 1.8 m x 1.8 m. In the last case, the crate runs diagonally from corner to corner. Most modern designs incorporate a section of steel mesh or slotted-plastic flooring at the rear of the sow.
Whatever the design, floors must remain dry. Artificial heating using gas, electricity or fuel oil is often necessary in creeps to keep litters warm, often incorporated into a kennel. However, it is equally important to keep the sow relatively cool.
The 'all-in, all-out' system, in which pens in separate rooms hold each weekly, fortnightly or monthly batch of farrowings, is commonly adopted to improve hygiene and reduce the effects of disease.
Weaners are often held in kennels or specially designed pens until 8-10 weeks of age. These are hygienic and warm, with controllable environments. From about 10 weeks of age, weaners are reared in the grower pens. It is not advisable to wean pigs directly into grower pens unless the environment can be adjusted to suit them. If adjustment is possible, leaving pigs in the same pen from weaning to market prevents the growth setbacks and stress problems associated with moving and mixing pigs.
In the case of small herds, it is usually convenient to rear one litter in each pen. The litter-sized pens give good results and keep stress to a minimum, but waste space. Batch farrowing enables the piglets to be mixed around the time of weaning - the earlier the better, so they become familiar. Two or more litters are kept in a pen until 10 to 12 weeks of age when they are divided according to size. To use the pen space most efficiently, five or more litters of similar age should be weaned together, and then divided and later subdivided according to size or sex. The number of pens required depends on the size of the pigs at market age.
In fully slatted pens equipped with single-space, wet-and-dry feeders, the preferred maximum depth is 4 m and the minimum practical width is 1.8 m. This allows for a shed width of 10 m with pens arranged back to back, service lanes on either side of the shed and a common effluent drain running down the centre of the shed.
In partly slatted pens, one-third of the floor area should be slatted. The total depth of the pens should be double the width. Preferably, they should also have:
- a slope of 1:25 on the concrete floor
- solid pen divisions on the concrete floor
- solid pen fronts and gates where pens face each other across a lane
- provision for pigs to see other pigs in at least one adjacent pen when standing on slats over drains.
There must be sufficient distances between the piggery, ponds, manure or used bedding disposal areas, and dwellings to prevent odours becoming a problem. Drainage from the piggery must not be allowed to enter a running stream.
Various local government regulations also relate to piggeries, and a licence may be necessary in some areas. Contact your local government authority for further information.
- Kruger, I, Taylor, G and Ferrier, M (eds) 1994, 'Plan it - build it', NSW Agriculture/Pig Research and Development Corporation, Tamworth, Australia.
- McGahan, E, Nicholas, P, Casey, K and Hopper, K 1998, 'Housing systems for dry sows and boars'