Pig reproduction: sexual maturity, cycle, gestation and farrowing

If you are wondering about pig breeding, look no further! This article explains how it happens in this animal, when sexual maturity takes place, how we identify the different phases of the cycle, and how gestation and childbirth go.

Pig sexual maturity

Males and females do not necessarily reach their sexual maturity at the same age because it depends on their growth. It is observed that sows can have their first heat around the age of 5 months. But generally, it is assumed that sexual maturity is reached around 6 months. Also, if you do not want the pigs to mate, you have to separate the males from the females early enough, or sterilize the males or females. This is important to avoid consanguineous matings. Note that in the Vietnamese dwarf pig, it is reached very early: at 2 months of age for males and at 3 and a half months for sows.

Just because a pig is sexually mature doesn’t mean it should be allowed to breed. What nature allows for the survival of the species is not always consistent with the welfare of the animal. In this case, if the sow gives birth before the age of 1 year, it will be detrimental to her future growth and health. If we take the case of a dwarf pig, it grows up to the age of 3 years. And in many species of mammals, gestation is a trying time for the body.

In addition, a sow that is too fat or too thin has a negative influence on the size of the litter. For an individual, this is probably less important than for a breeder, but this fact highlights the need for the sow to be in good health and to have reached a good weight for the gestation to go well. For a farm pig, the weight of the young sow should not be less than 60 kg, which usually corresponds to the weight reached at the age of 12 months. Conversely, it is not recommended to wait too long for the first service, because the sow is then often too fat and it is observed that not only she carries fewer piglets, but she raises them less well. The optimal breeding weight for a sow is therefore located between 60 and 90 kg.

Sexual cycle in sows

The sow is in heat every 3 weeks. But young sows have a little shorter heat. Like all mammals, the behavior of the female changes significantly over this period: the animal is more affectionate, invasive, and even aggressive. In a group, the sow frequently tries to climb on top of her fellows, she also has less appetite and she utters grunts for long periods. Some sows prick their ears or lift their tails in the presence of a male. Physiological signs can also be observed, such as enlargement of the vulva and the presence of sticky mucus there.

For its part, the pig is fertile all year round when it is not castrated. The animal is then less docile. Its behavior is more difficult to control than that of a castrated pig, with a tendency to run away and be destroyed. His body odor is also quite strong.


If the owner is profit-conscious, he or she will be careful that mating takes place during the second half of heat as ovulation usually occurs only towards the end of heat.

To ensure good fertilization, the boar (name given to the male pig used as a breeder), must be able to complete the service to its term, without being disturbed or chased by the sow. The breeding can take about ten minutes, or even a little more.

In the case of group breeding, in which the boar moves freely among the sows, there is no need to worry about the right time for the service because the boar is infallible to smell it. If breeding is tightly controlled, it may be necessary to ‘test’ the sow to make sure it is the right time: when presented with a male, she comes to a standstill at least for 10 seconds. More simply, it suffices to step over the sow (in a calm and silent context) to exert pressure on its back and to observe if a similar reaction is obtained: this is the so-called “rider” test.

It is known that it is necessary to organize a favorable context for reproduction. The boar should be handled as little as possible, not exposed to any unnecessary agitation. It should be avoided to transport it. If this turns out to be unavoidable, then it should be given time to regain a feeling of calm and security. In general, we must start from the idea that it is the sows that are brought to the boar, and not the other way around. To avoid accidents, you should also make sure that the floor of the breeding ground is not slippery. The act of breeding must take place without disturbance until its completion. If no new cycle starts 3 weeks after the first day of heat, you are sure that the mating was successful.


In pigs, it is customary to say that gestation lasts 3 months, 3 weeks, 3 days. Most sows give birth between the 114th and 118th day. Considering the length of cycles and for the welfare of the animal, it is important to ensure that the sow does not start a new gestation until next year.

Throughout this period, the sow must be fed appropriately so that she does not over-fatten. She also needs to be able to get enough exercise every day: care should be taken to keep her moving throughout gestation.

The birth

If you want to register your sows in the herd-book (the herd book of cattle and pig breeds), you must follow the first farrowing closely because it is only after that its registration can be done.

About 48 hours before farrowing, sows build a nest, also called a “cauldron”. It is the only ungulate species that builds a nest. If the sow has no straw or grass available, she will still pretend to build her nest. Rare are the breeders who provide them with this little material which could considerably improve their well-being. Straw also has the advantage of contributing to the thermoregulation of piglets. Heat lamps are often placed nearby as a supplement.

A few days before giving birth, udders and vulva swell. The mucous plug liquefies and comes out of the vagina. If the sow has not been isolated from the group a few days earlier, this should be done without delay.

The first pain occurs 3 to 6 hours before parturition. The sow fidgets more and more. The presence of the first piglet in the genital tract starts the actual farrowing: this will last between 2 and 6 hours. First-time sows will often need a little extra time. It is necessary to supervise the sows in order to be able to intervene in the event of complications. Piglets present at 5 to 30 minute intervals. Once the entire litter is born, we make sure that the little ones come to the suckling without too much delay. The placenta should be expelled 1 hour after the birth of the last piglet. It is frequently eaten by the sow.

1 to 2 days later, the birth canal continues to empty of a watery and mucous secretion of whitish color, odorless. If this is not the case, if it is of a different color, consistency or if it gives off an odor, a veterinarian should be consulted.