Rick Jones, Extension Animal Scientist
Farrowing and lactation are two of the most critical phases of pork production. A relatively high proportion of pig losses occurs during these periods. A greater understanding of the events which occur prior to and during the birthing process and lactation can lead to improved management of sows for increased litter size and weight at weaning time.
Farrowing marks the end of the gestation period in which embryos develop into baby pigs in an average time of 115 days. In individual sows or gilts, farrowing may occur outside the 113 to 116 day normal range without serious consequences. Shorter gestation lengths are associated with larger litter sizes. Genetic and management factors may also influence the time of farrowing. Before the delivery of pigs is possible, the sow's cervix must be dilated or enlarged to allow passage of the pigs. Also, the pigs must be moved down the uterus toward the cervical opening. These events are controlled by complex changes in hormone levels in the sow.
Any number of outward signs may be observed in the sow preparing to farrow. Nervous, restless behavior of the sow will usually be observed along with the instinctive nesting behavior (pawing at floor) that occurs even in confinement facilities without nesting or bedding materials. Muscular contractions of the flank, belly and tail are generally noted to some degree before delivery begins. The respiration or breathing rate of the sow may increase from a normal 25 to 30 per minute to as high as 80 per minute around five hours before delivery. Then the rate begins to fall.
As farrowing nears, the sow's udder becomes more distended and firmer and milk may be stripped from the teats. However, the consistency and abundance of milk may vary greatly from one sow to another. With much experience and some skill, you may be able to detect that milk is abundantly available and delivery of pigs is likely to be within six to eight hours.
During the movement of unborn pigs toward the cervical opening, the powerful contractions of the uterine muscles tend to break open the placental membranes which contain fluids and fetal feces or wastes (called meconium). In many sows, the fluids stained with blood will be expelled from the vulva and serve as a sign that farrowing will follow shortly (generally in two hours or less). Likewise, the greenish-brown meconium will sometimes be expelled shortly before farrowing. Both of these signs are useful in predicting the onset of delivery, but many sows will farrow without either sign.
Although no outward sign can be absolutely relied upon to predict farrowing, the experienced producer can certainly use these collective observations to plan attendance at most deliveries.
Proper knowledge of the hormonal controls of the farrowing process can improve farrowing results. It is currently believed that pigs developing in the uterus produce corticoid hormones which act on sow's uterine tissues, causing release of a compound called prostaglandin. Prostaglandin is carried from the uterus to the ovary, where it stops the production of progesterone and stimulates the release of relaxin for dilating the cervix. At the same time, prostaglandin is carried to the sow's pituitary glands and causes release of oxytocin into the bloodstream. Oxytocin causes contractions of smooth muscles in the milk glands (milk letdown) and in the uterus (expulsion of pigs). Stimulation of the sow's udder by nursing pigs or through rubbing by hand can stimulate release of oxytocin, causing further contractions for pig delivery.
If properly timed, injections of prostaglandin can result in normal deliveries. A ten mg injection of prostaglandin F2, or a similar synthetic compound, at day 110 of gestation (or later) will generally induce delivery of pigs about 27 to 30 hours later. Injections before day 110 will possibly increase the incidence of stillborn pigs. Precise breeding-farrowing records are necessary to safely use this hormone.
By artificially initiating the birthing process, producers can increase the percentage of farrowings which occur during the hours when workers are available to assist with this event. One typical scheme that could be used is to induce farrowing in all sows that are 110 days or longer into gestation by injecting on Monday mornings around 8 a.m. Most of these sows should farrow near midday on Tuesday. On Thursday morning, all sows which have not farrowed and are 110 days into gestation could be induced to farrow on Friday. The use of a synthetic prostaglandin to induce farrowing is not 100 percent effective but is a useful management tool.
There are at least two synthetic prostaglandins approved for this use in sows. The injection should be given in the neck muscle of the sow with a 1.5 inch needle to enhance complete absorption into the blood stream. Observance of all label precautions is especially important with this product.
Oxytocin injections can be used to supplement the effects of naturally occurring oxytocin. Avoid improper use by observing these guidelines:
Muscular contractions cause the actual delivery of pigs. The contractions expel the pigs from the uterus, through the dilated cervix and out the vulva. A distinctive twitching of the sow's tail may signal the movement of a pig through the birth canal. Delivery of the pig is considered normal whether the front feet and nose or the hind legs are first to exit the sow. In a mature sow, pigs may have to travel five to six feet from the far end of the uterus to the birthing point. During this trip, the umbilical or navel cord usually remains connected with the placenta and continues to supply enough oxygen for survival of the pig.
First born pigs generally have a greater opportunity to suckle colostral milk and have greater survival rates. Pigs located at the upper end of the uterus will usually be born last and have a greater chance of the umbilical cord becoming detached from the placenta during farrowing. This loss of an oxygen supply may result in dead pigs at birth, or weak pigs which may die later. The majority of fully developed pigs which are dead at birth (stillborns) actually die during (not before) the farrowing process. Stillborn pigs account for about 40 percent of total baby pig losses in some surveys. Therefore, any factor which will aid in a speedy, uncomplicated delivery of the litter will likely reduce pig losses significantly.
The average time interval between births of pigs is about 15 minutes, with a normal range of O to 30 minutes. Longer intervals are related to higher stillbirth rates or reduced vigor and survival of pigs. However, it is possible for a sow to begin farrowing, stop due to exhaustion, etc., and later finish farrowing normally.
Total delivery time from first to last pig may average about two and one-half hours. Table 1 outlines a suggested system for scoring sows for farrowing ease. Faster farrowing and fewer stillborn pigs correspond to a better (higher) farrowing ease score. Farrowings which require five or more hours should definitely be considered problem farrowings.
Use of a farrowing ease score system may bring attention to an existing herd problem and
stimulate solution of that problem. Heritability or genetic origin of the problem may be minimal,
but sows with serious farrowing problems should be culled. Farrowing problems (slow
farrowing) are often related to over-fatness, severe constipation, heat and other physical stresses.
|5||Farrowed and cleaned with no outside stimulus and less than 10 percent stillborn|
|4||Farrowed and cleaned with oxytocin injection and/or less than 20 percent stillborn|
|3||Needed physical assistance and/or up to 30 percent stillborn|
|2||Needed repeated assistance and/or more than one-third stillborn|
|1||Required caesarean or died during or shortly after farrowing|
Ideally, producers should select and manage sows for reduced farrowing problems so that farrowing assistance is not necessary. However, in practice, assistance at farrowing is necessary in most swine operations if a high degree of pig survival is expected. Assistance is needed to:
Detect and act upon problem farrowings. Dystocia (problem deliveries) occurs in less than one percent of the farrowings, so detection of the occasional problem may require experience. Try not to over-react or interfere unnecessarily with a normal farrowing. If the interval between pigs extends to 45 minutes or an hour, the attendant should be concerned enough to observe the sow closely. If the sow is having contractions without results, check the birth canal for possible blockage.
With a well-lubricated, gloved hand, carefully enter and search the reproductive tract for improperly presented (tail first or broadside) or extremely large pigs. Make every effort to prevent damage to the sow. Clip fingernails closely and use a non-irritating veterinary lubricant, not a common liquid soap. Clean the sow's external genitalia and enter the vulva with the fingers and thumb in a close, pointed formation. A slight rotating movement may assist entry. Some advantage may be gained by using the right hand if the sow is laying on her right side and vice versa.
If a pig is found in the tract, determine the orientation or position and apply pressure accordingly. Due to the limited space and slippery nature of the pig, it is often difficult to apply strong pressure for prolonged periods. Some pigs must be repositioned slightly to allow them to enter the birth canal. Time is important to prevent suffocation of the pig. Keep examinations of the sow's tract at a minimum to prevent edema and damage to the sow.
In many cases, an obstetrical tool may be necessary to pull large pigs. Special pig pullers, forceps or a simple nylon cord may provide the advantage necessary to extract the pig. Avoid attaching tools to parts of the pig's body which may be severely damaged. Use extreme care to prevent damage to the sow's tract.
If the pelvic opening is crowded by hardened feces in the sow's lower intestine, an enema may be necessary to gain space for easy passage of pigs in the adjacent reproductive tract. A full bladder may also interfere with normal delivery.
Occasionally, the uterus becomes blocked due to twisting or stretching, so pigs cannot reach the birth canal. If this problem is detected or suspected, make the sow stand up and walk around the farrowing house before allowing her to continue labor. If this does not yield results, get veterinary assistance.
If the sow stops straining and contracting before farrowing is completed, muscular exhaustion may be the problem. After a short rest, the sow may resume farrowing naturally or when aide by injected oxytocin. Keeping sows reasonably cool may help prevent exhaustion.
Prevent losses of pigs at birth. As many as 25 percent of the pigs which appear to be dead at birth (stillborns) may be saved with human assistance. First, clear the mouth and nostrils of the pig with the fingers or a cloth. To clear fluids from, and force air into the lungs, hold pigs by their rear legs and gently but forcefully sling them in a downward arc. Another method is to grasp the rear legs and pump them toward the abdomen while holding the pig's head downward. A manual respirator or a small funnel may be used to cover the pig's nose and force in air. A vigorous rubbing or massaging action may be the stimulus needed to get the pig breathing on its own.
Assistance at farrowing also prevents some losses of pigs trapped in sections of the placenta, although most pigs alive at birth will escape the afterbirth surrounding them. The spraddle-legged condition of newborn pigs may be aggravated by slippery floors and poor footing and may be prevented with assistance at farrowing.
Detect and prevent sow losses. Loss of one or more pigs during farrowing is unfortunate, but loss of the sow is serious and places the survival of all her pigs in doubt. Sows may die during farrowing due to internal bleeding from hemorrhaging blood vessels in the uterus. An extreme anemic appearance (pale skin, gums and eyelids) may warn of internal hemorrhages. However, excessive bleeding may not be apparent before death of the sow.
Prevent sow mortality due to excessive heat by making certain that ventilation and/or drip cooling equipment is operating correctly. Swab cool water along the jowl and udder of the sow, but never pour water on the head of an over-heated sow. A portable fan may be used to direct greater air flow to the over-heated sow. Large amounts of ice inserted into the rectum provide rapid cooling in emergency cases.
This final stage of the farrowing process generally passes without much notice. However, failure to expel the placenta may result in severe complications: infections, possible lactation failure, rebreeding problems and death of the sow. Some placenta passed during delivery of the pigs is normal, but most will pass immediately after farrowing or within several hours. The placenta often slips through slatted floors into the pit area, making it difficult to tell if a sow has expelled or retained the placenta. Reduced appetite or elevated rectal temperatures may be the first clue of a retained placenta.
Lactation or milk production is a function the sow must perform well to successfully rear the farrowed pigs. The udder of a sow consists of mammary or milk producing tissue and teats which serve as canals to give the pigs access to the milk. Ideally, these teats should be evenly spaced so the milk produced is divided equally among all teats. However, front teats are spaced more widely than hind teats. This possibly explains the greater milk production and faster growth of pigs suckling the front teats. Front teats are usually presented more fully to the pigs when the sow lays down to be nursed.
The establishment of teat order occurs soon after birth, and there is a tendency for a pig to continue nursing a certain teat until weaned. Some fighting to establish teat order continues during the first week of life and the smaller, weaker pigs may be forced to nurse the less productive rear teats. This further reduces their chances for survival. Select replacement gilts with an ample number (12-14) of functional evenly spaced teats. Presence of pin nipples, inverted nipples and nipples damaged by nipple necrosis will reduce the pigs' access to milk produced by the sow. Long, slender teats tend to provide a more secure nursing station, especially for small pigs.
Milk production or yield is affected by udder design as well as by nutrition, environmental temperature, genetics, mold toxins, diseases and other factors. Milk yield usually shows an increasing level up to approximately three weeks after farrowing and a decline thereafter. Milk yield and the composition of the milk is directly related to baby pig survival and growth. Feed intake of sows must be gradually gradually increased to avoid constipation, but full feed must be achieved by about five to six days after farrowing. Average daily intakes of 10 to 12 pounds are needed to promote milk production and avoid excessive weight losses. Weight of the litter at 21 days (peak of lactation) is a reliable measure of the sow's milking ability when adjusted for number of pigs nursed. Baby pigs can convert milk to body weight gain at an efficiency of approximately 4.0 to 4.5 pounds of milk to 1.0 pound of gain.
A peak daily milk yield of 15 pounds or about 2 to 2.5 gallons would not be unusual. Each milk "letdown" period lasts for 20 or 30 seconds and occurs at approximately hourly intervals. Nursing periods are slightly more frequent during the day (light periods) than at night (dark periods). The length and intensity of the light period (photoperiod) may affect total milk production. Sows exposed to longer light periods (16 hours/day) may produce more milk than sows exposed to a more restricted light period (8 hours/day). Longer light periods with more milk production should result in greater survival and heavier weights of pigs. Sows which are hungrily awaiting feeding may not allow pigs to nurse for extended periods of time.
The composition of sow's milk varies greatly due to stage of lactation, nutrition and genetics of
the sow. Colostral milk contains a greater concentration of immunoglobulin proteins increasing
the percent of solids and total protein in the milk (Table 2). As lactation progresses, the fat and
lactose (milk sugar) proportions increase and the protein decreases.
Table 2: Typical Composition of Sow's Milk
|Total solids, %||30.0||20.0|
Complete lactation failure (agalactia) is not found often in sows and gilts. However, lowered milk production (hypogalactia) is a common clinical sign or symptom possibly caused by many different factors. Disease organisms, hormonal imbalances, poor nutrition, mold toxins, and temperature stresses frequently cause hypogalactia. Improper management is often the underlying cause of hypogalactia. Lowered milk production causes direct and indirect pig losses: direct losses due to starvation, and indirect losses because undernourished pigs often scour or are laid on while trying to nurse.
Failure to produce adequate milk is found more frequently:
Hypogalactia may or may not be accompanied by mastitis (hot, hardened or swollen udders) and metritis (infectious discharge from the vulva). Treatment of hypogalactia varies somewhat with the suspected cause(s) of the problem, but is always aimed at quickly re-establishing milk flow to prevent pig losses. The main objective is to reduce inflammation with injected cortisone and reduce excessive edema (fluid collection) in mammary tissues. Injected oxytocin is used to remove the milk from the teat cisterns. Treatments which cause additional stress on the sow may further reduce milk production and milk let down. Water intake should be observed and feed allowances should be reduced then re-established.
Since recognition of hypogalactia in early stages is critical to survival of pigs, improving routine management is the only long term solution to this problem. However, new methods of increasing herd immunity have shown promise in reducing hypogalactia. Oral vaccines and feed-back of pig intestinal contents to gestating sows have substantially reduced lactation problems in some herds. Competent veterinary assistance is needed for these procedures.
One problem encountered during or after farrowing involves savaging, or the attempts of sows to bite or kill newborn pigs. This behavior problem may occur in confinement as well as in pasture-farrowed sows, but confined sows are more readily observed by the producer. Occasionally, a sow or gilt will bite and possibly kill first born pigs when they come around her head searching for a teat to nurse. Savaging occurs more often in overly fat sows or gilts and in certain breeds and family lines. Savaging may be the result of nervous reaction to the pain of the farrowing process or the strange, new farrowing surroundings the sow or gilt is exposed to. Although tranquilizers may be needed for extreme cases, removal of newborn pigs to a warm box until farrowing is complete may solve the problem. If pigs are removed, occasional hand stimulation of the udder may help to speed the completion of farrowing through natural oxytocin release. Return of the litter to the sow after farrowing should be done quietly with continued observation until the sow accepts nursing of the pigs. Savaging may account for some part of the early pig losses labeled as overlay by the sow. In severe cases, sows which continue to bite their pigs should be culled from the herd.
Lack of appetite, sickness, hypogalactia and constipation are frequently found at the same time in the farrowing house. It is difficult to establish cause and result relationships among these four factors, since each contributes toward the severity of the others. Prevent constipation by use of a laxative in the farrowing ration (see Extension Bulletin 854, Practical swine feeding ideas.). Sows which fail to form a stool by 24 to 48 hours after farrowing should receive a prescribed injectable or oral veterinary laxative, or the feed should be top dressed with two tablespoons of epsom salts (magnesium sulfate) or potassium chloride.
Lack of appetite in the sow is a symptom of sickness and/or constipation. If the sow is sick, the rectal temperature will often be elevated. Frequently, the sow's rectal temperature rises from the normal 102 degrees F (38.9 degrees C) to 103 degrees or 104 degrees F (39 degrees or 40 degrees C) after farrowing. However, if a temperature over 105 degrees F (41 degrees C) is observed, veterinary attention is advisable. Improve appetite and feed intake by using more palatable rations, more frequent feedings, or cooler environmental temperatures. Check the flow rate of waterers and the quality of water because water intake and feed intake are closely related.
Sow lameness is another post-farrowing problem caused by many different factors. Lameness generally results in poor lactation performance, reduced litter size and weight and possibly culling of the affected sow. Rough flooring can damage foot pads or cause cuts and scrapes. Any of these injuries can be infection sites for lameness-causing bacteria. Slippery flooring causes injuries and may discourage sows from attempting to get up, eat and move about. The "downer sow"syndrome is caused by breaks in bones (especially in the pelvic area) weakened by poor mineral or vitamin nutrition. These breaks and lamenesses often occur after weaning but may happen in the farrowing house. In rare cases, lameness or complete rear leg paralysis is caused by injuries received in delivery of extremely large pigs. This lame condition may be short-term, but sometimes the sow will not recover. Many of the sows may not recover sufficiently to salvage any market value.
Observations of the general activity level of the sow can indicate discomfort and the potential for poor sow performance. Excessively active sows may not allow adequate nursing and may be prone to stepping or laying on pigs. Mange, lice and the presence of stray voltage may contribute to excessive activity. Sows which rarely get up or eat and drink may be sick or lame and often do not produce adequate milk yields. It is a good idea to make sure that all sows get up every time you feed them.
A workable farrowing house management plan must be developed for each swine operation. Due to differences in facilities, breeding programs, management abilities and disease conditions, a standard management plan will not work. Constant evaluation of new ideas, management techniques and new products and equipment is required to develop the best possible management plan for an operation. The key to making this plan work is scheduled farrowing through a well organized production system.
The management plan in Table 3 summarizes recommended practices for good performance, health and comfort for the sow. These practices, along with good management of the litter, should result in increased litter size and weights at weaning and improved profitability. For information on management of the litter from birth through the nursery stage of production, see Extension Bulletin 871, Management of Young Pigs.
The Sow -- Improving Her Efficiency. English, P.R., W.J. Smith and A. MacLean. Farming
Press Limited. 1977.
|Days after breeding|
|100-109||Treat for lice and manage (refer to External Parasite bulletins for approved insecticides).|
|Deworm with dichlorvos, fenbendazole, levamisole or other broad spectrum dewormer|
|109||Move clean sow into farrowing crate, feed 4-6 lbs. laxative farrowing ration|
|113-116||Increase observation of sows, check for presence of milk and assist with farrowing|
|Days after farrowing|
|1||Limit sow feed intake to 3-4 lbs.|
|1-2||Check udders for signs of lactation failure or mastitis. Equalize litters by transferring pigs of same age into smaller litters.|
|2-7||Gradually increase sow feed intake by 2 pounds per day as long as the sow continues to increase intake|
|Check sows for appetite, rectal temperature, constipation and milk flow (observe nursing of pigs)|
|Reduce feed intake to 4-6 lbs. except in extremely thin sows.|
|Deworm and treat for lice and mange.|
Bulletin 872/March, 1986
The University of Georgia and Ft. Valley State College, the U.S. Department of Agriculture and counties of the state cooperating. The Cooperative Extension Service offers educational programs, assistance and materials to all people without regard to race, color, national origin, age, sex or disability.
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