By: Wayne L. Singleton, Purdue University
Farrowing is one of the most critical stages of the reproductive cycle, and it is important to have a good understanding of the normal farrowing process. Prompt detection and correction of problems can prevent sizable losses due to baby pig death at or around the time of farrowing. Extra care during this phase can impact the overall profitability of the operation.
Many types of farrowing pens or huts may be used, depending on what seems best adapted to the conditions on the farm. Pens or huts should be oriented with the door away from prevailing winds, and to take advantage of sunlight or shade in the appropriate season. The size should be sufficient for the sow to lie down on her side fully extended, with room for a large litter of growing piglets. Pen designs often include a guardrail or slatted space where piglets can escape the risk of crushing when the sow lies down. Maximum pen size depends on the climate and management practices. Smaller farrowing pens are better for retaining heat, while larger, taller pens are better for preventing the pen from getting too hot in warm seasons and climates. A hanging cover, such as burlap over the door to the pen, can be used in cold weather to help keep out the cold. Give consideration to the need to use artificial heat if winter lingers longer than expected.
Many breeders prefer to isolate the sow where she will not be bothered by other sows; however, some heritage breed pigs will naturally assist new mothers. If farrowing will take place where other pigs are present, keep a close watch until it is clear whether the culture of the herd is to help or hinder. Some heritage breeds in outdoor systems prefer to build their own nest. Use of the huts can be encouraged by having them in place with a thin layer of straw or other absorbent nesting materials at least 5 days before the expected farrowing date. If the hut is reasonably portable without a floor and the sow has begun nesting, the hut can be put in place over the nest.
Clean farrowing quarters greatly reduce the incidence of disease in newborn piglets. If farrowing is inside of a building, the area can be thoroughly cleaned and disinfected a few days before the sow enters. In outdoor systems, huts should be cleaned, disinfected and moved to a clean, dry area. Treat pregnant females for internal and external parasites about two weeks prior to farrowing. Wash the sows with warm, soapy water and move them to the farrowing quarters about 4 to 5 days prior to the expected farrowing date.
Phases of Farrowing
Normal farrowing is a continuous process. For descriptive purposes it is usually divided into three stages.
Stage 1. Preparatory Stage. This stage begins with muscular contractions and ends with complete cervical dilation that allows the fetuses to enter the pelvic or birth canal. The only outward signs of this stage are abdominal discomfort and restlessness.
Stage 2. Fetal Expulsion. This stage begins when the first fetus enters the pelvic canal, with visible abdominal contractions and ends with delivery of the last fetus. The time period from the first observed contractions until birth of the first pig is usually one to three hours, but may vary from several minutes to several hours.
Stage 3. Expulsion of Placental Membranes. Stage 3 completes the farrowing process. In the majority of farrowings, the placental membranes (afterbirth) are passed in one mass within one to two hours after the last pig is born. On occasion, a clump of placenta may be expelled before the last pig is born. Occasionally a piglet is born wrapped in its placenta.
Outward Signs of Imminent Farrowing
If farrowings are to be attended or if special management changes are to be made (i.e., provision of supplemental heat) it is important to be able to predict, within a few hours, when a sow is about to farrow. In situations where breeding dates are known, gestation length can be of use in predicting the time of farrowing. However, the gestation length of sows can range from 109 to 121 days. Some commonly observed signs and when they often show up are listed below. These may be useful in management decisions, especially if breeding dates are not known or if attending farrowing is important.
Signs that farrowing is imminent:
- Abdominal contractions (typically sow is in labor)
- Nest building/restlessness (starts 2-3 days before farrowing)
- Change in rectal temperature (increases 1 to 2 °F)
- Expulsion of blood stained fluid from the vulva (typically sow is in labor)
- Milk letdown (droplets often expressed for 2-3 days, if streams of milk expressed, farrowing will occur within 12 hours)
- Expulsion of fetal fecal pellets from the vulva (sow is in labor)
- Tail twitching (piglet is in birth canal)
Sow Behavior during Farrowing
Increased activity of sows during Phase 2 can have implications upon piglet survival because of the increased risk of trampling or overlying (sow lying on piglets). Newborn pigs are likely to be in close contact with the sow where they are at risk when the sow rolls from side to side or stands and lays down. As farrowing nears completion the sow normally becomes more docile and less active.
Duration of Farrowing and Time Interval between Pigs
Duration of farrowing, or time interval from the birth of the first pig to the last pig, may range from one to eight or more hours. There is a relationship between duration of farrowing and number of stillborn pigs in the litter. Sows which complete farrowing within two to two and one-half hours tend to have fewer stillborns than sows that have a longer duration. The average interval between live pigs is about 15 minutes, though they can come simultaneously or several hours apart. Recording birthing ease can be valuable when making culling decisions. A gilt with high incidence of farrowing difficulty or a sow with a high proportion of stillborn piglets, for example, should be carefully evaluated before giving them another chance to breed.
Presentation of Pigs at Birth
Pigs are born in both anterior (head) and posterior (tail) first positions in about equal numbers. There is no relationship between the type of presentation and the frequency of stillbirths of other farrowing problems.
The umbilical cord of most pigs remains attached to the placenta until the pig is delivered. After delivery the cord pulls apart, and the placenta usually remains in the uterus until farrowing is complete. However, as farrowing progresses, the incidence of ruptured umbilical cords increases, which contributes to an increased number of stillbirths toward the end of farrowing.
Pigs are born according to their location in the uterine horns. The pig closest to the uterine body is born first. Pigs in the left and right horn are delivered at random. Pigs may be born alternately between horns; i.e., two or three may be delivered from one horn and then two or three from the other, or occasionally all pigs may be expelled from one horn before any are expelled from the other horn.
Studies have shown that attended farrowings result in at least an extra pig weaned per litter. Of course it may not be practical or economical to provide for supervised farrowings around the clock. However, by understanding what is “normal” and what is “abnormal”, it is often possible to save pigs during the normal working hours. Examples include: removing the placenta from newborn piglets to prevent suffocation, moving a newborn piglet that is caught under the sow or one that has wandered to a cool corner of the farrowing area, assisting a newborn piglet that has the umbilical cord around its neck, and providing assistance to piglets that are having difficulties in obtaining their first breath of air. Oxytocin, a hormone, may be helpful in sows experiencing a difficult birth. Oxytocin stimulates contractions of the uterine muscles and helps in expelling the piglets. Massaging the udder can release endogenous oxytocin and is a preferred first attempt at increasing contractions, though oxytocin is also available to be used as an injectable. Never administer oxytocin until it is determined that there are no pigs stuck in the pelvic birth canal.
The incidence of stillborn pigs in many herds is five to ten percent of all pigs farrowed. Stillbirths are usually classified as prepartum (before farrowing) or intrapartum (during farrowing). Intrapartum deaths are the major cause of stillbirth pigs. Below are some observations related to stillborn pigs resulting from intrapartum complications.
- Stillborn pigs have the outward appearance of live littermates, but their lungs do not float in water.
- They are usually the result of noninfectious causes.
- Stillbirths increase as duration of farrowing increases. More stillbirths occur toward the end of farrowing, in the last third of the litter. This is especially true for older sows and for larger litters.
- Pigs located at the ovarian end of the uterine horn have a higher incidence than those located near the uterine body because they are born later in the birth order. More pigs located at the ovarian end are born with ruptured umbilical cords.
- Pig fetuses have a low tolerance for anoxia (lack of oxygen). Brain damage or death can occur within five minutes after umbilical rupture or impeded umbilical blood flow (crimped cord). Many pigs born weak have suffered from anoxia, and their survival rate is low.
- Stillbirths tend to be either the lightest or heaviest pigs.
- In one study, the average time interval between one live pig until the next live pig was 17 minutes, and the time interval from a pig to a stillborn pig was 47 minutes.
Post-Farrowing Pig Behavior
Following birth, pigs get to their feet and instinctively make attempts to reach the udder within minutes. Most pigs suckle within 45 minutes following birth. Within a few hours, piglets begin to establish a “teat order”. This is a tendency for larger piglets to select or “claim” front teats while smaller piglets are relegated to the rear teats, and by 2-3 days post-farrowing piglets will nurse exclusively their select teat the remainder of lactation. Front teats are more popular for the following reasons:
- Greater security. Piglets are safer from kicking.
- Front teats secrete more milk.
- Milk “let-down” may be more easily stimulated.
- Spacing between teats is generally greater.
- Teat length is longer.
- Front teats are more available and better exposed.
Remember there is a considerable difference in size between the sow and her piglets, so care should be taken to reduce crushing. Creating a warm creep area away from the sow, using ‘guardrails’ in the farrowing pen or a farrowing crate, and keeping piglets dry and free of drafts help save pigs. Keeping the area dry can dramatically reduce bacterial contamination. Bacterial loads lead to increased incidence of scours, and piglets can become dehydrated quickly once scouring. The sow should be fed a highly palatable diet balanced for her expected level of milk production. The goal is to work her up to full feed rather quickly, and feeding sows more frequent meals can help achieve that. Assuring the sow also has ample cool, fresh water will go a long way to increasing feed intake. Remember that she will prefer a temperature of 55-65 ºF, while for the first few days her piglets are more comfortable in the 90-95 ºF range. Sows will normally lay on their side once piglets are born. When it is time to nurse, about once hourly, they initiate a distinctive grunting that alerts the piglets. The stockperson needs to recognize what is normal so they know when it is time to call for help. In many areas of the country help is available from local Extension offices, the herd veterinarian or other farmers. Some additional resources to consider reading are listed below.
For more information:
Natural farrowing behavior of the sow and her piglets https://porkgateway.org/resource/natural-farrowing-behavior-of-the-sow-and-piglets/
How to Raise Pigs. P. Hasheider, 2008. Voyageur Press.
Storey’s Guide to Raising Pigs. K. Klober, 2008. Storey Press.
Stockmanship. Lammers, P. J.., D. R. Stender, and M. S. Honeyman, 2007. Niche Pork Production publication NPP710. Available from: http://www.ipic.iastate.edu/publications/710.Stockmanship.pdf
Care of the sow during farrowing and lactation. Pork Industry Handbook, PIH 46
Baby pig management- birth to weaning. Pork Industry Handbook, PIH 18