Determining the number of pens and stalls required in a pig unit
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One objective in planning a pig unit is to balance the accommodation between the various ages and number 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.
Determine the farrowing interval and number of farrowings per year.
- Average weaning to conception interval 20 days
- Gestation 114 days
- Suckling period (7x8 weeks) 56 days
- Farrowing interval 190 days
Number of farrowing per sow per year 
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 weaners 28 days
- Cleaning and sanitation of pen 7 days
- Occupation per cycle 98 days
Thus one farrowing pen can be used for 
farrowing per pen.
A 14 sow herd with an average of 1.9 farrowings per sow and year requires 
farrowing pens.
Determine the number of servicing / gestation 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 farrowing a year
27/2.7 = 10 places would be required.
Determining 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
Determining the number of places in the growing / finishing accommodation:
One stage finishing
- Fattening of pigs 12 to 27 weeks of age (25 – 90kg) 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:
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.
places are 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 cleaning ( the emptying period will be shorter if the pigs are sorted for size while being transferred from the growing to the finishing pens)
places are required in the unit.