Housing for non-lactating sows
During gestation, the sow requires close attention to her needs. Sows may be kept indoors, either on deep litter or floors with some slats, or outdoors with access to shelters. The 'Model code of practice for the welfare of animals: pigs (3rd edition)' outlines standards and recommendations for their care. This section provides information about housing for dry sows in general and constructing a stall.
A gestation building need not be elaborate as long as it meets animals' and operators' basic needs. The building should be relatively draught free, well insulated and well ventilated. The welfare code recommends a temperature between 15 and 30oC to provide an optimum range at pig level. Ideally, dry-sow shed temperatures remain between 18 and 24oC, depending on air speed, flooring and whether the sows are in groups. Elevated temperatures affect both boars and sows, resulting in high returns to service, low litter numbers and abortions. Low temperatures can reduce body condition or increase feed requirements. While mature pigs generally tolerate low temperatures, sows in individual stalls cannot huddle or move out of draughts, so they need better management.
Galvanised iron or aluminium are common materials for dry-sow shed roofing, and a range of insulation products can be used. The life of galvanised iron is directly related to the thickness of its zinc coating. The thickest coating class (Z600) is recommended. However, products with zinc-aluminium coatings are not recommended as cladding for intensive pig housing.
Buildings should be oriented with their long axis running east to west, with eaves on the northern and southern sides. The distance between buildings should be more than four times the height of the tallest building to ensure adequate ventilation.
The walls may be constructed of timber, brick, concrete, sheet metal or any combination of these. Cladding should be installed 900 mm above floor level, and shutters, louvres or blinds fitted in the remaining space to roof height. In hotter climates, it is more common to open the full height of the side for ventilation, covering the opening (which has a fence to keep the pigs within the shed) as needed with blinds (often automatically controlled in larger sheds) or twin shutters.
Concrete floors should not be excessively rough or slippery. They must be smooth with a uniform slope of approximately 1:25 to the slats for drainage. A strong, durable floor may be achieved with 30 MPa concrete and F62 steel reinforcing mesh. No admixtures or fly-ash should be used in the concrete as they may reduce durability. A continuous polythene membrane installed beneath the concrete slab will prevent moisture rising through the floor. Moisture rising through the concrete makes the floor cold and damp.
Pens, gates and lanes need to allow pigs to move easily. Preferably, these gates open to enable a number of animals to pass at once (possibly the full width of the pen), open across the full width of the laneways, and latch easily and securely.
Spray cooling is a very effective way to cool sows and boars. A spray of large droplets may be directed over the slatted area of stalls (over the resting area in deep-litter systems) for two to three minutes every half hour when the temperature reaches the maximum desired temperature (usually 26oC). The pigs cool down as the water evaporates from their skins. Fans also assist in cooling the pigs. Various types of insulation are available to help keep pigs within their thermal comfort range.
Individual sow stalls
Individual sow stalls enable the sows to receive close attention for part of their gestation or individual feeding. In future, under the welfare code, sows may be confined to a stall for only six weeks of gestation except when under veterinary advice or special care of a competent stock person.
Typical purpose-designed gestation buildings have two rows of stalls, a central feeding passage and an access lane at the rear of each row. Buildings that house large herds often incorporate multiples of the double-row system. The stalls may be used for feeding sows kept in groups and may be short or full length. Full-length stalls may have gates to close the stall to enable the slower eaters to finish without being bullied. Each sow may have a stall or groups of sows may be taken to the same set of stalls for feeding.
Individual sow stalls:
- enable individual feeding so that each sow can be fed according to their body condition and weight
- provides sows with freedom from bullying by other pigs
- enables activities, such as veterinary attention, to be performed easily.
The floor of a sow's stall is usually concrete at the front, with slats covering a trench at the rear. The slats may extend over some or all of the rear access lane. They may run either across or along the trench. In the latter case, the first slat adjacent to the rear of the stalls may be removable to enable manure to be cleared efficiently. In part-slatted stalls, the slats should be level with the floor. On certain sites, an almost fully slatted design may be justified, although some food may be wasted unless it is dampened. Concrete slats are preferable in this situation, as sows' biting and gouging can quickly damage timber slats at the front of a stall.
Timber may be used, though concrete or glazed earthenware slats last longer and reduce maintenance. Over time, timber can become too smooth for stable footing. Hardwood slats measuring 100 mm x 25 mm are fixed to hardwood bearers measuring 100 mm x 50 mm with galvanised twisted pallet nails and a 25-mm gap between the slats. With some timbers, a narrower gap is advisable to allow for shrinkage. Cross trench bearers should be placed at similar intervals to the stall panels to enable manure to be cleared efficiently. Hardwood slats are usually sawn from ironbark timber but other highly durable timbers free from sapwood are suitable.
Concrete slats are constructed from strong and durable reinforced concrete. They are usually 100 mm deep and taper from 125 mm at the top to 90 mm at the base. There is a gap of 25 to 32 mm between the slats for dry sows. The top surface of the slat should have a non-slip finish but not be rough enough to damage the sows' feet and knees. The slats should not have sharp edges.
Flushed manure trenches have no slope along their length, and hold water due to a 25 to 50 mm nib wall at the downstream end of the trench. A trench depth of 200 to 300 mm below the bottom of the slats is recommended. These shallow trenches are flushed once or twice daily. The trench should be divided along its length into channels no more than 600 mm wide by baffles 150 mm high. This prevents the flushing wave curving around accumulations of dung.
The welfare code requires new stalls to be a minimum of 600 mm x 2200 mm for sows (700 mm x 2400 mm for boars), and for all stalls to provide the standards outlined in the code; for example, enough space for pigs to stand and lie without touching the stall. The lower rail of each panel should clear the floor by 200 mm to give the sow leg room while lying down.
The recommended stall design requires a shielded panel with vertical bars that extend from the front of the stall back for half its length to prevent aggression between sows. The panel should not be solid as this prevents normal social interaction and restricts air movement around the sow. If mesh forms the panel, it needs an aperture of 75 mm x 50 mm or smaller. The framework is constructed from 20 mm galvanised pipe. Stalls usually have fronts sloping at 60° to prevent the sow climbing and make feeding easier. Having one or more jump rails over the front of the stalls is also generally included.
A baffle projecting from the dividing hurdle downward into the common trough prevents fighting along the trough, and theft or passing of feed between sows, but should not inhibit the flow of water along the trough.
Stalls should be of 'rear-entry, front-exit' design because sows prefer to walk out rather than back out of stalls, and it is easier for both sows and operators. The recommended minimum width of the laneway at the rear is 600 mm.
Tubular steel gates or chain breeching (5 mm galvanised long-link chain) are normally used when the rear lane is also slatted. If the rear lane is solid concrete, solid rear access doors should be fitted so that manure and urine are deflected onto the slats in the stall.
Feeding and watering can be combined in a single trough serving each row of stalls. Troughs may be constructed of concrete, steel, glazed earthenware, concrete or fibre cement half-round piping. Water is dispensed from a tap or float valve at one end of the trough. A plugged outlet 'S' drain should be fitted at one end to make regular trough cleaning easier. Alternatively, water may be supplied individually through nipple drinkers.
Research is continuing into group housing and the best methods for mixing sows, such as time after weaning and mating, and pen design characteristics. A variety of methods is used for herds, such as mixing the next batch before putting them in with a larger group, and ensuring quiet and low stress (not mixing) immediately after mating and pregnancy recognition/embryo implantation for at least 14 days, and preferably about 28 days after mating.
The welfare code´s minimum space allowance is 1.4 m² for sows in group housing and 1 m² for selected or mated gilts over 100 kg. The code recommends that small groups (less than 10 sows) need greater space if persistent bullying and aggression occurs. In practice, larger space allowances may be used in particular circumstances, such as 1.5 m² or 2 m² for gilts and 2 m² or more for weaned sows, to improve the percentage being stimulated to puberty or oestrus.
Small group penning
Groups of 3 to 12 sows are kept together in pens, usually in their selection or weaning group. Advantages include the opportunity for exercise and huddling. Disadvantages include a lack of control over the sows' individual feed intake, increased opportunities for fighting and bullying, and difficulty in managing individual sows.
Group pen/stall combinations
Having a combination of stalls (full or partial) within a pen enables sows to come and go as they please. The full stalls may have lockable back gates that may be opened in bulk. This system attempts to have the advantages of both systems without their disadvantages. However, it does increase the shed area required to contain the same number of sows, which is consequently more expensive.
Large group penning
If large numbers of sows are kept together and totally housed, the floor may be solid concrete with slats at one end or deep-litter design. Short side walls protrude into the shed space, providing extra walls for sows to lie against. Sows are fed in a variety of ways, including on the floor, in a trough, in groups, in individual sow stalls (full or partial, potentially with lockable back gates and some solid floored areas) or by electronic feeding. With electronic feeding, sows have access to a computer-controlled feed station. Each sow is individually identified by a radio transponder on her collar or ear. The computer receives a signal from each sow's transponder when she enters the feeding station and releases a preset amount of feed. The system combines the freedom of movement and social interaction of group penning with the control of individual feed intakes. The system requires skilled management for it to work properly, including minimising aggression.
Shelters in paddocks
Sows require shelters in paddocks to protect them from the weather. The shelter should have enough space to enable less dominant sows to obtain a place. Secure housing may be required to protect sows from predators overnight. The welfare code recommends 1.2 to 1.5 m² per sow.
Pre- and post-mating housing
Sows and gilts to be mated should be kept near but not next to (more than 1 m and within 5 m) the pen of a mature boar. This assists with the onset of oestrus and ease of access to the mating area for stimulation, oestrus checking (possibly twice daily for greater stimulation and better timing of mating) and mating (natural and artificial insemination). Pens, lanes and gates must enable pigs to move easily.
Each sow pen or stall should have a card or blackboard showing sow identification information, mating date, return date, due farrowing date and the amount of daily feed required. In a row of pens or stalls, the cardholder or blackboard can be mounted on a swivel and read from either front or rear laneways.
Plan for constructing a dry-sow stall
Plan for constructing a dry-sow stall
- Provide the sow's daily feed requirements.
- Make water freely available.
- Minimise bullying. This is very important during the first few weeks of pregnancy while the embryos are implanting.
- Provide adequate shelter to protect sows from temperature extremes, inclement weather, sunburn and photosensitisation, which can cause early abortion and delays in conception.
- Look after sows' health and wellbeing. This includes ensuring that sows are maintained by feeding, and efficient disease prevention and control, in hygienic surroundings.
- Set up the operation for ease of management. Good working conditions for operators help to maintain a high standard of husbandry. Routine but essential activities, such as record keeping or veterinary attention, need to be performed regularly. Likewise, mating must be supervised and recorded, the workload of boars controlled and recently mated sows provided with a quiet area to help improve conception rate.