Farrowing is the term for a sow (female pig) giving birth. It covers the entire process, from the early signs of labor through delivery of piglets and expulsion of the afterbirth. Modern sows deliver an average of about 11 to 13 piglets per litter, and the whole process typically takes around seven hours from start to finish.
The Three Stages of Farrowing
Like labor in other mammals, farrowing unfolds in three distinct stages. The first stage is preparatory: the cervix softens and dilates while the uterus begins contracting to position the first piglet in the birth canal. This stage isn’t always obvious from the outside, though the sow may seem restless or uncomfortable.
The second stage is active delivery. Strong abdominal contractions begin, the fluid-filled sac around the piglet ruptures, and piglets are expelled one at a time. On average, a new piglet arrives roughly every 20 minutes, though this can vary widely. When birth intervals stretch beyond 20 minutes consistently, the risk of stillbirth rises. Total delivery time across the full litter averages about 411 minutes (just under seven hours), but shorter farrowings generally produce healthier litters.
The third stage is the passage of the afterbirth, or fetal membranes. In pigs, pieces of membrane sometimes come out alongside individual piglets rather than all at once at the end.
Behavioral Signs Before Farrowing
Sows give fairly reliable signals that farrowing is approaching. The most recognizable is nest-building behavior, which typically starts about 24 hours before delivery. The sow becomes noticeably more active, pawing at bedding, rearranging straw, and changing posture far more frequently than normal. If you were tracking her movements, you’d see a sharp spike in position changes during that final 24-hour window.
In the last few hours before the first piglet arrives, activity peaks and then drops off. Once farrowing begins, the sow becomes relatively still, and for the first 24 hours after delivery her movement stays very low as she nurses and rests.
Hormones Driving the Process
Two hormones do most of the heavy lifting during and after farrowing. Oxytocin drives the uterine contractions that push piglets through the birth canal. It also plays a role in nest-building behavior before labor starts, essentially priming the sow’s body and brain for delivery. After farrowing, oxytocin triggers milk ejection each time piglets nurse.
Prolactin handles the other side of the equation: initiating and sustaining milk production throughout lactation. It also influences nursing behavior, making the sow more responsive to her piglets. Together, these two hormones coordinate both the physical delivery and the transition into motherhood.
Why the First Hours Matter for Piglets
Newborn piglets are born without meaningful immune protection. They depend entirely on colostrum, the thick first milk the sow produces, to acquire antibodies. The critical threshold is about 250 grams of colostrum per piglet. Below that amount, mortality rates jump dramatically, from around 5–7% to as high as 20–43% depending on the study. Most piglets consume two-thirds of their total colostrum within the first 12 hours after birth, making that window essential.
Even so, an estimated 10–30% of piglets in a litter don’t get enough. Smaller or weaker piglets often lose out in competition with larger littermates, especially in today’s larger litters. This is one of the biggest challenges in modern pig production.
Temperature Needs in the Farrowing Area
One of the trickiest parts of managing farrowing is that sows and piglets need very different temperatures. Sows are most comfortable between 15 and 20°C (59–68°F). Anything above 25°C (77°F) causes heat stress, which reduces feed intake and milk production. Piglets, on the other hand, prefer temperatures around 35°C (95°F) and are highly vulnerable to hypothermia at birth.
The standard approach is to keep the farrowing room at about 22°C (72°F) during and just before delivery as a compromise, then lower it to 18–20°C (64–68°F) over the following days. Piglets get supplemental heat from heat lamps or heated mats in a small area of the pen where they can warm up without overheating the sow.
Farrowing Crates and Housing
Farrowing crates are metal enclosures that restrict the sow’s movement during and after birth. Their primary purpose is preventing the sow from accidentally lying on and crushing her piglets, which is the leading cause of piglet death before weaning. The crates were originally designed with a target of keeping pre-weaning mortality below 10%.
They work. A large meta-analysis found that piglet mortality is about 14% higher in open pen systems compared to crates. But the trade-off is significant: sows in crates can’t turn around, can’t build nests properly, and show signs of frustration and stress. This has driven growing interest in alternative pen designs that give sows more freedom while still protecting piglets, though no current open design fully matches the crate’s mortality numbers.
Recognizing Farrowing Complications
Normal farrowing progresses steadily, with piglets arriving at reasonably regular intervals. Dystocia, or difficult birth, occurs when labor stalls or a piglet can’t pass through the birth canal normally. Warning signs include prolonged straining with no piglet appearing, excessive restlessness or signs of exhaustion in the sow, and abnormal discharge such as foul-smelling or bloody fluid.
As a general guideline, if no piglet has appeared after an extended period of active pushing, or if the gap between piglets stretches well beyond the typical 20-minute average, something may be wrong. Larger litters, which are increasingly common in modern genetics, carry higher risk because the sheer length of delivery means later-born piglets spend more time without oxygen. Farrowings lasting over 300 minutes (five hours) are associated with increased stillbirth rates.
Sow Care After Farrowing
A lactating sow’s water needs are substantial: 5 to 10 gallons per day. Dehydration after farrowing directly reduces milk output, which in turn affects the entire litter’s growth and survival. Ensuring the sow has constant access to clean water and begins eating again within the first day is one of the simplest and most impactful things a farmer can do.
Sows typically nurse their litter for three to four weeks before piglets are weaned. During this period, the sow’s body draws heavily on its own reserves to produce milk, losing significant body condition. Adequate nutrition during lactation sets up both the current litter’s health and the sow’s ability to breed again successfully.