Pig Housing

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Pig farming is realtively unimportant in most regions of Africa, as in most tropical countries, except China and South-East Asia. However, pig production is increasing in many tropical countries as processed pork finds an increasing market and pig production yields a relatively rapid rate of return on the capital employed. Pigs are kept primarily for meat production, but the by-products, such as pigskin, bristles and manure are also of economic importance.

To some extent pigs compete with man for food, but they can also utilise by-products and wastes from human feeding.

Management Improvements

In many tropical countries pigs roam freely as scavengers or are raised in the back-yard where they depend on wastes for feed. Little attempt is made to obtain maximum In many tropical countries pigs roam freely as scavengers or are raised in the back-yard where they depend on wastes for feed. Little attempt is made to obtain maximum productivity. However, a few simple management practices can help to improve the productivity and health of these pigs. They include:

1 Fenced paddocks with shade and water where:

2 Simple semi-covered pens constructed of rough timber with a thatch roof and floor of concrete as shown in Figure 10.25. An earth floor can be used, but is more difficult to keep clean and sanitary. Several pens can be arranged in a row as required. The main disadvantage with this type of accommodation is the relatively high labour requirements for cleaning.

3 Wallows or sprinklers can be provided to alleviate heat stress. Being unable to sweat sufficiently pigs have a natural instinct to wallow to increase the evaporative cooling from the skin.

Figure 10.25 Smallholder's pigsty for one sow with litter or 4 to 5 fattening pigs.

While such improvements have the advantage of low investment in buildings and less need for balanced feed rations, they should only be regarded as first steps in raising the general level in present primitive systems.

The raising of pigs in confinement is gradually replacing the old methods because of lower production costs, improved feed efficiency and better control of disease and parasites. Thus, the confinement system is usually advisable in circumstances where:

Some systems keep only part of the herd in confinement. The order of priority for confinement housing for the different classes of animals is usually as follows:

Management Systems in Intensive Commercial Pig Production

There is no standard type or system of housing for pigs. Instead, accommodation and equipment are chooser to suit the type of management system adopted. However, there are certain similar principles and practices in most systems. These originate from the fact that most pig units will contain pigs of different ages and classes as show in Figure 10.26.

Farrowing-Suckling Pens

In small and medium scale intensive pig production units a combined farrowing, suckling and rearing pen is normally used. The sow is brought to this pen one week before farrowing and stays there together with her litter for 5 to 8 weeks when the piglets are weaned by removing the sow. The sow is often confined in a farrowing crate a few days before, and up to a week after birth to reduce piglet mortality caused by overlaying or trampling. Systems 1 and II in Figure 10.27.

Early weaning after a suckling period of 5 to 6 weeks or even less can only be recommended where management and housing is of good standard.

The piglets remain in the farrowing pen after weaning and until they are 12 to 14 weeks of age or weigh 25 to 30 kg.

Group keeping of farrowing-suckling sows that have given birth within a 2 to 3 week interval is possible, but is unusual in intensive production. However, there are few acceptance problems and the litters cross-suckle and mix freely. The pen should have at least 6mē deep litter bedding per sow, with an additional creep area of 1mē.

In a large scale unit, which has a separate farrowing house, sometimes either of the following two alternative systems ate practiced instead of the system described above:

The first alternative (System III in Figure 10.27) is similar to the system already described, but the piglets are moved two weeks after weaning to a weaner pen where they may remain either until they are 12 to 14 weeks of age (25 to 30 kg) or until 18 to 20 weeks of age (45 to 55 kg). Note that the piglets should always remain in the farrowing/ suckling pen for a further 1 to 2 weeks after the sow has been removed so that they are not subjected to any new environmental or disease stress at the same time as they are weaned. The weaning pens can contain one litter or up to 30 to 40 pigs. The pigs are often fed 'ad libitum'.

Figure 10.26 Flow Chart of the life cycle or pigs.

In the second alternative showing (System IV in Figure 10.27) the sow is placed in a farrowing crate in a small pen one week prior to birth. Two weeks after farrowing the sow and the litter are moved to a larger suckling pen. The piglets may remain in this pen until 12 to 14 weeks of age or be transferred to weaner accommodation two weeks after weaning.

Dry Sow Pens

After weaning a sow will normally come on heat within 5 to 7 days and then at 3 week intervals until successful mating. The average weaning to conception interval can vary between 8-20 days depending on management. In the period until pregnancy has been ascertained the sow is best kept in a pen or stall in close proximity to the boar pen.

Gestating sows are kept in yards or pens in groups of up to 10 to 12 sows, that will farrow within a 2 to 3 week interval. They can also be kept in individual pens confined in stalls or tethered in stalls.

Weaner and Fattening Pens

The weaners, whether they come from a farrowing pen or a weaner pen, will at 12 to 14 weeks of age be sufficiently hardened to go to a growing/finishing pen. Finishing can be accomplished either in one stage in a growing/ finishing pen from 25 kg to 90 kg - systems 1 and IV in Figure 10.27 or in two stages so that the pigs are kept in a smaller growing pen until they weigh 50 to 60 kg and are then moved to a larger finishing pen where they remain until they reach marketable weight. System II in Figure 10.27. In large scale production the pigs are arranged into groups of equal size and sex when moved into the growing/finishing pen. Although finishing pigs are sometimes kept in groups of 30 or more, pigs in a group of 9 to 12, or even less, show better growth performance in intensive systems. An alternative, where growing and finishing are carried out in the same facility, is to start about 12 pigs in the pen and later, during the finishing period, reduce the number to 9 by taking out the biggest or smallest pigs from each pen.

Figure 10.27 Flow chart of four different management systems in the pig production.

Replacement Pens

In intensive systems a sow will, on average, produce 3 to 6 litters before she is culled because of infertility, low productivity or age. Young breeding stock should be separated from the rest of the litter at about 3 months of age, since they should be less intensively fed than the fatterning pigs. Gilts are first covered when they are 7 to 9 months of age or weight 105 to 120 kg. After mating they can either be kept in the same pen up to 1 week before farrowing, or kept in the gestating sow accommodation, but in a separate group.

Boars in the tropics are usually quiet if run with other boars or with pregnant sows, but may develop vicious habits if shut up alone.

Determining the Number of Pens and Stalls Required in a Pig Unit

One objective in planning a pig unit is to balance the accommodation between the various ages and numbers of pigs. Ideally, each pen should be fully occupied at all times, allowing only for a cleaning and sanitation period of about 7 days between successive groups.

In the following example the number of different pens required in a 14-sow herd, where 8 week weaning is practised, will be determined.

I Determine the farrowing interval and number of farrowings per year.

Average weaning to conception interval 20 days
Gestation 114 days
Suckling period (7 x 8 weeks) 56 days
Farrowing interval 190 days

Number of farrowings per sow and year 365 / 190 = 1.9

2 Determine the number of farrowing pens.

The piglets remain in the farrowing pen until 12 weeks of age.

Before farrowing 7 days
Suckling period 56 days
Rearing of weaners 28 days
Cleaning and sanitation of pen 7 days
Occupation per cycle 98 days

Thus one farrowing pen can be used for: 365 / 98 = 3 7 farrowings per year.

A 14 sow herd with an average of 1.9 farrowings per sow and year requires (14 x 19) / 3.7 = 7 farrowing pens.

3 Determine the number of servicing/ gestating pens.

Average weaning to conception interval 20 days
Gestation period less 7 days in farrowing pen 107 days
Cleaning and sanitation of pen 7 days
Occupancy per cycle 134 days

Thus one place in the servicing/gestation accommodation can be used for: 365/ 134 = 2.7 farrowings per year.

With a total of 27 farrowings a year

27/2.7 = 10 places would be required.

4 Determine the number of places for replacement stock.

Presume the sows on average get 5 litters, then 20 percent of all litters will be from gilts.

Rearing of breeding stock (12 to 35 weeks) 168 days
Gestation less 7 days in farrowing pen 107 days
Cleaning and sanitation of pen 7 days
Occupancy per cycle 282 days

About 30% more animals are separated than the required number of gilts thus the required number of places in the 14 sow herd will be

(14 x l.9 x 0.2 x 1.3 x 282) / 365 = 6 places

5 Determine the number of places in the growing/finishing accommodation:

One stage finishing:  
Fattening of pigs 12 to 27 weeks of age, (25-90 kg) 105 days
Extra period for last pig in the pen to reach marketable weight 21 days
Cleaning and sanitation of pen 7 days
Occupancy per cycle 133 days

Assuming that 8 pigs per litter will survive to 12 weeks of age the number of places required in the finishing accommodation will be:

(14 x 1.9 x 8 x 133) / 365 = 78

That is 8 pens with 10 pigs in each or 10 pens if each litter should be kept together.

Two stage growing/finishing unit:

Growing pigs 12 to 20 weeks of age will occupy a growing pen for 63 days including 7 days for cleaning.

(14 x 1.9 x 8 x 63) / 365 = 37 places is required in the unit.

Finishing pigs 20 to 27 weeks of age will occupy a finishing pen for 70 days including 14 days emptying period and 7 days for cleaning. (The empyting period will be shorter if the pigs are sorted for size while being transferred from the growing to the finishing pens.

(14 x 19 x 8 x 70) / 365 = 41 places is required in the unit

From the above example it will be appreciated that the number of pens of various kinds required in a pig unit is based on a number of factors. It is, therefore, not possible to lay down hard and fast rules about the relative number of pens and stalls. However, a guide line to the requirement of pens in herds with average or good management and performance in tropical conditions is given in Appendix VI.

Space Requirement

In intensive pig production systems all pigs should be raised on concrete floors to provide for a clean and sanitary environment. In semi-intensive systems a concrete floor is only used in the pens for finishing pigs and perhaps in the farrowing pens, whereas an earth floor or deep litter bedding is used in other pens and yards. Litter may or may not be used on a concrete floor, but its use is desirable, particularly in farrowing pens.

Because of the cost of a concrete floor there is a tendency to reduce the floor area allowed per animal. However, too high stocking densities will contribute to retarding performance, increasing mortality, health and fertility problems and a high frequency of abnormal behaviour thus endangering the welfare of the animals. Increasing the stocking density must be accompanied by an increased standard of management and efficiency of ventilation and cooling. In particular, to aid in cooling, finishing pigs kept in a warm tropical climate should be allowed more space in their resting area than is normally recommended for pigs in temperate climates. Table 10.9 lists the recommended space allowance per animal at various stocking densities. The figures listed for high stocking density should only be used in design of pig units in cool areas and where the management level is expected to be above average.

The dimensions of a pen for fattening pigs are largely given by the minimum trough length required per pig at the end of their stay in the pen. See Table 10.10. However, the width of a pen with low stocking density can be larger than the required trough length. This will reduce the depth to 2.0 to 2.4m, and thus the risk of having the pigs create a manure are within the pen.

Furthermore, the flexibility in the use of the pen will increase and the extra trough space allow additional animals to be accommodated temporarily or when the level of management improves.

Sometimes finishing pens are deliberately overstocked. The motive for this is that all pigs in the pen will not reach marketable weight at the same time and the space left by those pigs sent for slaughter can be utilized by the remainder. Such over-stocking should only be practiced in very well managed finishing units.

General Requirements for Pig Housing

A good location for a pig unit meets the following requirements: easy access to a good all-weather road; welldrained ground; and sufficient distance from residential areas to avoid creating a nuisance from odour and flies.

An east-west orientation is usually preferable to minimize exposure to the sun. Breezes across the building in summer weather are highly desirable. A prevailing wind during hot weather can sometimes justify a slight deviation from the east-west orientation. Ground cover, such as bushes and grass, can reduce reflected heat considerably, and the building should be located where it can most benefit from surrounding vegetation.

A fairly light well drained soil is preferable, and usually the highest part of the site should be selected for construction.

Pig houses should be simple, open sided structures as maximum ventilation is needed. A building for open confine merit is therefore essentially a roof carried on poles. The roof supporting poles are placed in the corners of the pens where they will cause least inconvenience. A free span trussed roof design would be an advantage but is more expensive.

In some circumstances it may be preferable to have solid gable ends and one tight side to give protection from wind or low temperatures, at least for part of the year. If such walls are needed they can often be temporary and be removed during hot weather to allow maximum ventilation. Permanent walls must be provided with large openings to ensure sufficient air circulation in hot weather. If there is not sufficient wind to create a draught in hot weather, ceiling fans can considerably improve the environment.

The main purpose of the building is to provide shade, and therefore the radiant heat from the sun should be reduced as much as possible. In climates where a clear sky predominates, a high building of 3m, or more, under the eaves gives more efficient shade than a low building. A wide roof overhang is necessary to ensure shade and to protect the animals from rain. A shaded ventilation opening along the ridge will provide an escape for the hot air accumulating under the roof. If made from a hard material the roof can be painted white to reduce the intensity of solar radiation. Some materials such as aluminium reflect heat well as long as they are not too oxidized. A layer of thatch (5cm) attached by wire netting beneath a galvanised steel roof will improve the microclimate in the pens. A roof of thatch is excellent in hot climates, particularly in non-confined systems, but cannot always be used because of fire hazard and because it is attractive to birds and rodents. A pig house with two rows of pens and a central feeding alley would require a ridge height of 5 to 6 metres if covered with thatch.

Table 10.9 Dimensions and Area of Various Types of Pig Pens


Stocking density

  Low Medium High
A. Farrowing/ suckling pen.
Resting area, if weaner        
pens are not used 10.0 7.5 6.0
Resting area, if weaner pens are used 8.0 6.0 5.0
Manure alley width m 1.7 1.5 1.3
Farrowing pen (System IV) m: - 4.5 4.0
Farrowing crate, length excl. trough m 2.0 2.0 2.0
width depending on size of sow m 0.65 - 0.75 0.6 - 0.7 0.55 - 0.65
free space behind the crate m 0.4 0.35 0.3
Piglet creep (incl. in resting area) 2.0 1.5 1.0
B. Boar pen
1. Pen with yard        
Resting are (shaded) 6 5 4.5
Yard area (paved) 12 10 08
2. Pen without yard 9 8 7
C. Gestating sow pens
1. Loose in groups of 5 - 10 sows        
Resting area (shaded) 2.0 1.5 1.1
Yard area (paved) 3.5 3.0 2.5
Feeding stalls, depth x width m 2.0 x 0.6 1.8 x 0.55 1.7 x 0.5
2. Individual stalls with access to manure alley, length of stalls excl. trough m 2.2 2.1 2.0
width of stalls m 0.65 - 0.75 0.60 - 0.70 0.55 - 0.65
width of manure alley m 1.5 1.4 1.3
3. Confined in individual stalls        
length x width of stalls m 2.2 x 0.70 2.1 x 0.65 2.0 x 0.60
D. Weaner pen (to 25 kg or 12 wks)
Resting area excluding trough mē/pig 0.35 0.30 0.25
Manure alley width m 1.0 1.0 1.0
0E. Growing pen (to 40 kg or 17 wks)
Resting are excluding trough mē/pig 0.5 0.45 0.40
Manure alley width m 1.1 1.1 1.1
F. Finishing pen, resting area excl. trough
For porkers to 60 kg or 21 wks mē/pig 0.70 0.60 0.50
For beaconers to 90 kg or 27 wks mē/pig 0.90 0.75 0.60
For heavy hog to 120 kg or 33 wks mē/pig 1.0 0.85 0.70
Manure alley width m 1.2 - 1.4 1.2 - 1.3 1.2

The pen partitions and the 1 metre wall surrounding the building, which serves to reduce heat reflected from the surrounding ground, can be made of concrete blocks or burnt clay bricks for durability or perhaps soil-cement blocks, plastered for ease of cleaning. Regular white washing may improve the sanitary conditions in the pens.

Doors have to be tight fitting and any other openings in the lower part of the wall surrounding the building should be avoided to exclude rats. Apart from stealing feed and spreading disease, large rats can kill piglets.

For all types of confinement housing a properly constructed easily cleaned concrete floor is required. Eighty to 100 mm of concrete on a consolidated gravel base is sufficient to provide a good floor. A stiff mix of 1:2:4 or 1:3:5 concrete finished with a wood float will give a durable non-slip floor. The pen floors should slope 2 to 3% toward the manure alley and the floor in the manure alley 3 to 5% towards the drains.

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