One of the advantages of farming pigs is their ability to reproduce more often than other livestock species. Sows can produce more than two litters per year making them a highly productive species.
The life cycle of a pig from conception, to birth, through growth and then slaughter can take up to 310 days. Pigs breed at all times of the year, regardless of the season. However, pigs can be affected by seasonal infertility in the warmer months. Once a sow has been mated, the production cycle commences. It is completed when those piglets reach ‘sale weight’. This marks the completion of the growing/finishing phase and the pigs are sold.
Pig production cycle length
The production of pigs can be divided into six life stages:
- Breeding/mating: gilts (female pigs that have not previously farrowed or given birth) are usually introduced to boars around 25–28 weeks old. The boar will often have daily exposure to young gilt’s to ensure they begin their reproductive cycling, with the gilts typically reaching puberty 10–30 days after commencing boar contact. Hormones can be used to stimulate puberty in gilts, but are rarely used. Boar exposure is the preferred and most effective means of bringing a gilt onto heat. Gilts will then usually be mated at their second cycle (when they go on heat for the second time) or around 30–34 weeks. Sows, or female pigs who have already farrowed, will have boar exposure to determine if they are on heat. Female pigs will either be mated with a boar naturally or will be artificially inseminated. The objective is to ensure the breeding females will have a long and productive life in the breeding herd, which means responsible animal welfare and treatment.
- Gestating or dry sows: after the sows and gilts are mated, they are moved into the dry sow or gestation area of the breeder sheds or paddocks. They will remain there during most of their pregnancy (approximately 116 days).
- Farrowing or birth: about a week before giving birth, they are moved into the farrowing or birthing sheds or paddocks.
- Lactation: sows remain in the farrowing area, nursing their piglets for about 3–5 weeks until the piglets are weaned.
- Weaning: after weaning, the sows are returned to the breeding area. The piglets are moved to weaner accommodation. The pigs can only be moved into the weaner facilities once the pens or sheds have been emptied of pigs by the producers moving these pigs to the next suitable area or to sale. Generally, the sheds are cleaned, sterilised and rested for 24 hours, before the next group of pigs arrive.
- Growing/finishing: depending on the farm, the growing pigs may be moved to other grower accommodation either on the same farm or a different facility. This is where the pig will live until it reaches ‘sale’ weight.
The farm structure
In pork enterprises, producers may specialise by concentrating on one or more stages of the production cycle. This means that modern farms can be either a farrow-to-finish farm (all the above stages on-site), a breeder farm, a weaner farm or a grower/finisher farm.
Some farms may be single site. Farms distributed across many sites are referred to as ‘multiple-site’ piggeries with each site linked to the others. The different classes of pigs are managed separately to provide for their specific requirements. Hundreds of kilometres may separate the breeding and growing facilities.