Parallel farrowing pens
A sow feeding piglets in a farrowing pen. Kennel with heat lamp on far side of crate.
- provide a place for the sow to have her litter
- minimise the risk of the sow trampling and crushing piglets
- encourage the sow to lie down slowly and carefully, reducing the risk of her trapping and crushing piglets
- keep the space requirement economical
- provide a hygienic environment.
The 'Model code of practice for the welfare of animals: pigs' (3rd edition) provides a guide to minimum space allocations, crate dimensions, and other standards and recommendations.
The farrowing pen's design must be based on the sow and her litter's requirements. Farrowing pens vary in design from a simple set of rails or gates that restrain the sow's movement to more complex pens that may have movable floors and different styles of gates. Research is still continuing into designs.
This article describes one type of farrowing pen.
Farrowing crate design
The overall length is defined as the distance from the front of the trough to the back partition of the crate or gates. This dimension is important for pen and building design, but is not a reliable guide to the amount of space available to the sow.
The code recommends a minimum length of 2000 mm, which includes feed and water facilities, and any rear anticrush rail. It also states that crate bars and fittings must not obstruct the sow from standing or lying down.
The effective length accounts for the length and height of the trough and rear gate arrangement. As a guide, it is measured from the inside of the rear of the crate to the point on the trough where 150 mm clearance from the floor is achieved. If the trough height is less than 150 mm long, the length is measured from the sow side of the trough. This is based on measurements made on sows varying in parity from one to nine at the National Agricultural Centre Pig Demonstration Unit (UK). This showed that 1950 mm of effective length was necessary and that 250 mm of clearance was needed under the trough to accommodate the sow´s head without it becoming trapped. If only the snout was allowed underneath, the clearance would be 140 mm, with the bottom of the trough sloping upwards towards the sow. These measurements may need revising to suit the type of pig and very large sows.
Width and available width
The crate must give clearance for the width of the sow´s body, enabling her to stand and, more importantly, rise without being able to turn around (until the gates are opened, in some designs, once the newborn piglets are familiar with the pen). There must be sufficient available width for the sow to lie comfortably in the suckling position. The code requires a minimum width of 500 mm at not more than 450 mm above floor level.
Bottom rail configuration
The bottom rail configurations include fixed or adjustable, straight or cranked rails, and expanded rails or prongs. The height for a fixed bottom rail is between 230 and 250 mm. If the clearance is greater than 250 mm, the young sows are likely to become stuck under the rail. The prong design and expanded rails have become popular, as they better suit a wider range of sows in varying sizes, and ensure that the piglets have access to the udder. An available width of 750 mm is suitable for most sows when lying, and the practical limit for crate width expansion with either expanded lower rail or prongs is 250 mm (125 mm on each side).
An appropriate prong number, spacing and floor clearance are all vital for satisfactory operation. The first three prongs from the front of the crate are spaced at 250 mm to prevent the sow getting her head trapped between a prong and the trough. The remainder are spaced at 300 mm. The clearance between the end of the prong and floor should be 150 mm for the rear-most two pairs of prongs to give the sow extra room for leg movement. The rest need a floor clearance of 80 mm. The minimum number of prongs required is five, while six is the maximum.
The height of the rail should be no more than 150 mm, with a width of 750 mm from the bottom rail opposite (similar to the width between opposite prongs). In other words, the bottom rail is expanded out by 100 mm from the rail above on each side. As a sow tends to lie with her back against a solid object - in this case, the bottom rail - there is ample room for the piglets to access the sow´s teats.
Feedback suggests expanded rails are easier to clean than prongs.
Rear gate or rump rail
The rump rail (a ´gate´ of vertical bars between horizontal bars) is attached between the lower rails at the rear of the crate to keep the sow's hindquarters clear of the back wall during farrowing, and to ensure that newborn piglets have room to move after birth. Clearance under the rump rail should be at least 170 mm so the farrowing is not obstructed. The maximum height for a horizontal rump rail is 250 mm to prevent injury to the sow. The separation of the vertical rump bars should be 200 mm. The rump rail can be removed after farrowing.
The crate's internal height should not be less than 900 mm, which should be adequate for most sows. Antijump bars can be fitted across the top of the crate to prevent the sow rearing on her hind legs; however, this must not obstruct the sow from standing.
Farrowing pen design
Many piggeries install parallel farrowing crates on fully slatted floors to simplify construction, and prevent problems with wet floors from drinker spillage and piglets dunging in the wrong corner. A board floor (preferably part of a kennel) is usually supplied for the piglets to lie on and help them keep warm. Occasionally, one is provided for the sow on a temporary basis.
Another common alternative is a pen with 900 mm of slotted area at the rear and a 300 mm wide section of slotted area at the front to collect drinker spillage.
The internal width of the farrowing pen should be at least 1800 mm to allow sufficient space for the sow and litter to eat and sleep in comfort.
The farrowing crate is usually offset in the pen, with approximately 750 mm of clearance on the creep side and 450 mm on the other. The pens should be laid out in the shed so the creep areas of each pair adjoin. This enables the common pen partition to be removed for litter mixing, and simplifies observation and heating connections.
A nearly fully enclosed creep area is recommended to stop draughts, and reduce energy use and heater capacity. Heating may be supplied by infra-red gas, electric or water-heated pads, as well as electric radiant bars or bulbs. The creep box is usually constructed from waterproof ply, with a hinged lid for easy observation.
Pen partitions and gates need to be constructed from solid sheet material to reduce draughts. Partitions should be 600 mm high. A convenient method of mounting is to fix the panels in channel section slides to enable the partitions to be easily removed for cleaning or litter mixing.
Floors should be easily cleanable and warm´, and provide grip without being abrasive. Perforated floors in farrowing pens need a high void ratio and maximum gap width of 10 mm. Commonly used floor materials are high-tensile steel mesh and plastic tiles. The use of timber is decreasing as it is becoming scarcer and more expensive. Concrete floors become harder to clean as they age; though,when kept in good condition, they are suitable especially for smaller herds.
Sows and piglets require separate drinkers. Sows need either a bite-type nipple or bowl waterer. Piglets need a small bite-type nipple that operates at reduced pressure.
The sow´s feeder should be designed to limit spillage, and be easily removable and cleanable. A separate feeder is required for introducing piglets to creep feed. A long-life material, such as 304-grade stainless steel, may be considered for the sow´s feeder construction.
Example plan and sectional elevations of parallel farrowing pen (length dependent on trough height and sow requirement)
Isometric view of a parallel farrowing pen (with three rails instead of four for clarity)