Reproductive Statistics for Swine
Age of puberty
4 to 7 months
150 to 175 pounds
Avg. 21 days
2 to 3 days
Standing when hand pressure placed on back
12 to 36 hrs from onset of standing heat
Age of puberty
150 to 175 pounds
1 boar : 25 sows
One of your biggest problems with your breeding program will be underweight or overweight pigs. Your boars should
be kept fit but not overweight, they can insure the sows. Your sows should not become overweight, it will affect their
ability to produce. Just like humans, they need to be fit.
Your boar is extremely important!
A boar must possess both the genetic potential to improve the performance of his progeny, and the physical soundness
to remain an active breeder. So far as overall improvement is concerned, a boar has far more influence in a herd than the
average sow. Because a boar has such a tremendous influence within a herd, careful consideration should be given to his selection,
management and replacement.
The development of a young boar's confidence is vital. Intimidation by a group of gilts or sows,
or even an attack by a large sow can be a devastating experience for a young boar. Reluctance to work is the usual result.
To develop his confidence a gilt or preferably a small quiet sow, of similar size, on ‘standing heat’ should be
used for the first few services. If the gilt or small sow does not stand for the boar it can lead to frustration, injury or
disinclination to work. Boars reluctant to work or lacking libido are a nuisance. They upset mating programs, resulting in
the overuse of other boars or the need to run extra boars.
Time of mating
Mating is best carried out in the early morning before feeding. Serving on a
full stomach can impose unnecessary strain. Also, the boar is more active in the early morning, particularly during hot weather.
The actual number of services and their timing is dictated by whether oestrus detection is carried out once or twice
daily. Two services 12–18 hours apart usually give better results than either a double service 24 hours apart, or a
single service. Triple services can be used if litter size is considered to be low. Plan the third mating for about 12 hours
after the second.
It is preferable to take the sow to the boar, as she normally
assumes the major role in searching out the male. This initial contact is important in replacing the social contact behaviour
with the sexual behaviour sequence.
Also, shifting the boar can excite him and make him difficult to control. However,
if a specialised mating pen is made available, the boar will become accustomed to the routine, but ensure that the boar is
placed in the pen and the sow is brought to him. Service crates can be used where small sows or gilts have to be mated to
a much heavier boar, but their success varies and depends a good deal on the attitude of the boar.
When a sow is introduced to a boar, the boar will approach her, emitting characteristic grunts.
She may run from him and he will follow, continuing to grunt, grinding his teeth and producing foaming saliva. He may urinate
frequently. He attempts to make contact with her and if she stops he may nose her flank quite forcefully, sniff the ano-genital
region and her head, and then attempt to mount.
If the sow responds by adopting the mating stance (standing immobile,
back arched with ears cocked), it is a signal to the boar that she is receptive and he will mount and copulation will occur.
Ejaculation is signalled by tightening and relaxing of the anal sphincter and should last at least 3 minutes. If any less
than that, the mating should be considered doubtful. The boar signals the end of copulation by dismounting.
This is easily overlooked but there is nothing that will give more trouble than a rough or slippery floor.
It is particularly common when the pen is used to house the boar and doubles as a service area. During mating, if the floor
surface is slippery, a sow may have difficulty standing for the boar. She could easily slip causing severe injury to herself
or to the boar. When a boar mounts a sow, his hind feet are often placed level with or in front of the sow’s feet. As
he thrusts, he gains leverage from his feet. If he happens to slip, he could easily injure himself. During ejaculation the
boar is immobile but if the floor is slippery, he may fail to complete the service and become frustrated. The floor should
be hard and well finished but not slippery. Providing a service area covered with sawdust, rice hulls or similar material
provides excellent mating conditions.
A common cause of a reluctance to work is the overuse of a boar or the abuse and overuse of young boars. It is important
to emphasise the need to supervise a young boar’s first services, to make sure they are successful and that he is in
no way injured or frustrated. This initial period will influence his subsequent mating behaviour. Boar mating sheets should
be used to keep a record of the services performed by individual boars. Used properly, they should prevent overuse of boars
and help detect sterility.
Make sure boar pens are positioned next to newly weaned sow pens, to maintain interest and activity.
Overfeeding, besides being wasteful, limits the usefulness of a boar and makes him lazy. This can be exaggerated during
periods of high temperatures. High temperatures do affect libido and stamina, and provision of wallows, sprinklers or cooling
should be provided. Infection or injury can also lead to a reluctance or inability to work. Sore feet and injury to the muscles
or ligaments of the back are not uncommon. ‘Rest and test’ should be the order of the day.
The useful working life of a boar can extend to about 3–4 years of age, but by then he becomes too heavy to mate
anything but old sows. He is more prone to leg weakness and his breeding ability and value is doubtful. In order to maintain
young active boars that are easy to handle, boars should be culled when they reach 3 years of age. As far as genetic
progress is concerned, it is more desirable to replace boars when they are 18 months of age. Where possible, boar replacements
should be planned in advance. Far too often young boars are brought in and expected to immediately perform like a mature boar.
A boar has a tremendous influence on a farm’s productivity and profitability. In order to maximise the herd’s
performance and throughput, boars should receive careful attention.
Farrowing or Parturition - Initiation of Farrowing
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.
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
Delivery of Pigs
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.
Lactation and Post-Farrowing Problems - Lactation
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.
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.
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.
|Table 3. Recommended Farrowing Management Plan* |
|Days after breeding
||Treat for lice and manage (refer to External Parasite bulletins for approved insecticides).|
||Deworm with dichlorvos, fenbendazole, levamisole or other broad spectrum dewormer|
||Move clean sow into farrowing crate, feed 4-6 lbs. laxative farrowing ration |
||Increase observation of sows, check for presence of milk and assist with farrowing|
|Days after farrowing
||Limit sow feed intake to 3-4 lbs.|
||Check udders for signs of lactation failure or mastitis. Equalize litters by transferring pigs of same age into smaller
||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.|
|*The sow health-vaccination program must also fit into the management plan. Each producer must
develop this program with veterinary assistance. |