You should consider the following points when you are selecting young gilt pigs to be kept for breeding purposes. Selection should be done when the pigs have reached bacon weight, so that the breeding gilts can be moved out of the fattening pens, and the remainder sold as baconers.

  • Health and Longevity:  Select from strains or families in the herd that have reared two good litters a year for three or more years in succession.
  • Prolificacy:  Strains or families that have produced good litters of strong healthy pigs.
  • Mothering Qualities:  Which depend on the temperament and milking qualities of the sow. Some breeds are better mothers than other breeds, an example being the Essex breed which are good mothers. Temperament has a fairly high heritability so that a quiet sow can pass this trait onto her offspring. Good milking capacity can be affected by the breed of pig but is affected much more by the feeding and management of the sow while she is feeding her litter.
  • Good Food Converters:  Select from strains or families that are good con­verters of food into meat. This quality is measured by the food conversion ratio (e.g. 1kg of live-mass gain for 2,8kg of meal eaten) and by the number of days required to reach bacon weight.
  • Good Carcass Qualities or Good Conformation: 
  • At least 12 well-spaced teats.
  • Good Length – a nice long pig for bacon production.
  • A fine shoulder, not too broad across the top.
  • Fine, silky skin which is a sign of good health.
  • Good, strong legs and feet.
  • No abnormalities.

All the above qualities should be judged under conditions of good management and feeding so that the full genetic potential of the growing pig can be seen.


Breeding gilts are selected at bacon weight (90kg live weight) and up to this stage they should be fed in the same way as the other fattening pigs in the pig unit. The table below shows the amounts of feed given to pigs up to bacon weight under two different systems.

With one system the pigs are housed indoors and fed only meal and the other system is for pigs being allowed out onto good pasture grass.

Live-massMeal OnlyMeal and Grazing
Up to 45kgAd lib1.5kg

After selection for breeding, keep the gilts at this level of feeding, but do no allow them to become too fat. Gradually switch them from bacon meal to sow meal.


Once the gilts have been selected for breeding they should be removed from the fattening pens and either run together in well-fenced, grass paddocks or run in yards. Gilts from different litters should be put into paddocks or yards all at the same time. Never introduce a few gilts into a mob of strangers otherwise they will be bullied and attacked. This period should be used to ‘harden off’ the gilts, giving them time to get used to exercise, and to living with strange gilts from other litters.


Bought in gilts need special care and attention, firstly because they have come to a completely new home with different systems, feeds, etc., and secondly, because in most cases they encounter a new bacterial environment. Every pig unit has its own type of bacterial population, and the stock bred and reared on a farm will have a built in immunity to many of the bacteria and viruses present. Unfortunately, the immunity acquired on one farm will often not protect the pig if it moves on to another farm. A period of ‘integration’ into the herd is therefore essential in the case of bought in gilts, so that the gilt will be immune to infertility viruses, to viruses connected with abortion, and to the coliform organisms that cause trouble at farrowing time. Experience has shown that the following management practices are well worth while.


Oetstrus: a period when a female animal will accept a mate.

The time of mating will depend on the size of the gilt rather than her age, but provided she has grown well and is the normal size for her breed, the gilt can be mated at 7-8 months old weighing about 130kg. At this time the gilt should be moved from the paddock or yard to the service pen within sight and smell of the boar. Oestrus is manifested in several ways, i.e. keen interest in the boar, swelling and reddening of the vulva, restlessness and possible mounting her companion gilts. To ensure that the gilt is fully on heat a ‘riding test’ can be given by putting the weight on the gilt’s back and if she is fully on heat she will stand firmly, with the handler sitting on her back. Oestrus lasts for 50- 60 hours and the optimum period for fertility lasts for 24 hours. The boar should serve approximately 12 hours after heat detection, i.e. if the gilt is on heat during the afternoon, she is served the following morning and again in the afternoon. The service should be observed and care taken that the service is completed before recording details of sire etc. Use a young boar which is not too heavy for the gilt.


Farmers sometimes find that 7 – 8 month old gilts for some unaccountable reason do not come on heat, for perhaps several weeks. When this occurs, a good tip is to sprinkle 100gms fish meal on to their morning feed each day. Keep it up for three weeks and more often than not, the gilt will come into season. If this does not work, try putting the gilts into a trailer and taking them for a run. Very often they will come onto heat within a day or two afterwards. Why such practices work is not known, but they are well worth trying when the problem exists.


Continue the integration of the gilts into the herd by housing the gilts with the sows as soon as possible. In a cubicle or stall system keep them side by side with sows. In a yard system, a gate between groups of gilts and sows is sufficient.

At oestrus the female pig will shed up to 20 eggs which are fertilized by the boar. How many of these fertile embryos survive to be born as live piglets will depend very largely on the feeding and management of the pregnant gilt or sow.



The boar is the most important single animal in the herd because half his genes will be carried by all his offspring. When selecting a boar, pay attention to the following points:

  • The boar must have a good conformation for the breed, and pay particular attention to his feet and legs.
Prepotent: a breeding animal that shows great effectiveness in transmitting hereditary characteristics to its offspring.
  • He must have at least 12 even and well spaced teats.
  • Always use boars that have been performance tested and in the case of an older boar, one that has been progeny tested. Try to find a boar that is prepotent.

On arrival a boar newly arrived from performance testing will need careful attention. He will probably be missing his companion in the testpan and needs quiet handling and observation whilst settling into his new surroundings If the boar arrives straight from the test at 5 ½ – 6 months, he should be housed on his own for the first month and to avoid frustration, sows and gilts on heat should not be adjacent. He should be wormed and a mange wash or spray used on arrival.


Care with the first few feeds is necessary and encouragement to get him eating his new food together with his bowels working correctly is essential particularly if he has travelled a long distance.

2.0 – 2,8Kg of a sow and weaner ration daily in two feeds is the normal recom­mendation and wet feeding will usually tempt him rather than dry meal. Keep him in hard active condition and do not allow him to become fat and sluggish.


The minimum area for lying, feeding, and dunging and exercise is about 30sq metres, but daily exercise during the first few weeks is recommended and during this time his handler will be able to get to know him and vice versa. Some time spent in handling him will be an advantage later in his life. The boar should be ready for service at 7.7 months. He should be within sight and smell of the gilts, preferably in a cubicle house. The area where the services are to take place should be free from any projections which could cause injury. The floor, if concrete, should be of wood float finish to prevent slipping and should not have a rough or flinty surface. Bedding is advised. If service takes place outside, the ground surface should be free from loose stones and not slippery.


The boar must never be introduced to a group of females and his first service should be preferably with a small sow or gilt well on heat, and standing firm, and this will prevent frustration which can arise when the gilt will not stand and constantly moves about.

Care must be taken to see that correct entry is made and guidance is sometimes necessary. The young boar must not be overworked and no more than two services per week should be the rule for the first few months of his breeding life.

If an abnormality is present or the boar is lacking libido when the females are standing well on heat, then veterinary advice should immediately be sought. It should be borne in mind, however, that most problems arise when the initial settling in period of the boar’s life has been neglected, or one or more of the management points overlooked.

A boar’s active breeding life can be extended by keeping him in a lean fit con­dition; however, replacement boars should be ordered well in advance to avoid buying in haste or using the new boar prematurely because of a sudden collapse in the established breeding programme involving the older stock boars.

Summary of Management Points for Boars

  • Rear up to 90kg live-mass in the same way as for bacon pigs. This is the performance testing period. After reaching 90kg live-mass, boars should be kept on their own to prevent fighting. Change the ration from bacon meal to sow and weaner or sow meal, and introduce some green food. This change of ration should be done gradually. Allow plenty of exercise, and up to 3,5kg of meal for a large boar each day, fed either wet or dry and in two feeds a day.
  • Boars can be housed indoors, or run outside in a pen or paddock with the dry sows. With indoor housing the dry sows should be kept in a pen next to the boar pen so that he can see and smell the sows as they come on heat. This is the best way to avoid being missed for service when they come on heat.

Boars running outside with dry sows in a pen, or paddock get plenty of exercise and should serve the sows as they come on heat and are ready to stand for service. Problems with this system are that two or more sows may be on heat together, and the boar will serve only one of them. It is also difficult to keep accurate records of service dates for all sows.

Progeny Test: evaluation of the breeding value of an animal by examining the performance of its progeny

A young boar can start serving at 7-75 months ld and gradually be worked up to full use at 18 months old. The sooner a boar is used, the sooner his offspring can be inspected and tested – in other words, the boar’s Progeny Test can be carried out.

An adult boar can deal with twenty sows a month, serving each sow once daily. If farrowings are spread evenly throughout the year, one boar can be used for 40 – 50 sows, being used about once a week.

In practice,

1 boar is worth keeping with over 8 sows in a herd

2 boars are worth keeping with over 30 sows in a herd

  • Boars can be kept for up to four years, but often have to be replaced earlier. Reasons for replacing a boar are:
  • He is having to be used on his own gilts.
  • He has become too fat and heavy to serve younger and smaller sows and gilts.
  • He has gone off serving, or is taking too long to serve his sows.
  • He has become bad tempered and savage and is too dangerous to keep any longer.


During the period between weaning and farrowing the sow must be fed and managed so that she achieves the following:

  • Dries off quickly and stops producing milk completely;
  • Comes on heat, is mated and becomes pregnant as quickly as possible after weaning;
  • Releases a large number of ova for fertilization and retains the maximum number of these ova so that she produces a good litter of pigs and;
  • Is kept in a good, healthy condition during pregnancy so that she farrows down with a good litter and plenty of milk to feed her little pigs.


When a sow is weaned at 8 weeks, the udder becomes engorged with milk which, together with the removal of the suckling stimulus, is responsible for milk production ceasing. This, in turn, is then responsible for the start of the reproduction cycle. With 5 week weaning, however, the piglets are removed at the time when the sow’s milk yield is often at maximum, and the pig farmer must often step in to assist nature and to ensure that the sow suffers no discomfort caused through an excess of milk.


To cut down the daily feed over the last few days of suckling unless the sow is in poor condition. On the day of weaning move the sow to another pen, give her no food and only a little water for 24 hours. After 24 hours allow free access to water and feed 3,6 kg of sow meal a day until the sow has come on heat and been served.


Keep up full feeding until the day of weaning. Move the sow to another pen away from her little pigs, starve her for 24 hrs and restrict the water. If she shows signs of producing milk on the second day after weaning, add 1 tablespoon of epsom salts (magnesium sulphate) to her water to reduce milk production. As soon as her udder goes down, allow free access to water and feed 3,6 kg of sow meal a day.


Sows will come on heat 3 – 7 days after weaning. As soon as the sow has dried off, she should be move into a pen near the boar, or into a yard or paddock running with the boar. Feed. 3.6 kg of meal a day to bring the sow onto a rising plane, of nutrition before she is served – this is known as ‘flushing’ the sow, and helps her to produce the maximum number of ova at ovulation. The number of little pigs in a litter is established when the sow is served.

The period of oestrus or heat lasts for three days and during that period the sow will actually stand for the boar over a period of two days. Standing can be tested by placing the flat of the hand on the sow’s back and pushing. If she is not ready for service she will walk away, but if she is firmly on heat she will stand firm. The normal signs that a sow is in oestrus are:

  • The vulva will, in most cases, become swollen and turn a bright red. Keep in mind what has been said about the timing of the service, as it is not uncommon for stockmen to rush for the boar as soon as this sign is noticed.
  • It is quite usual for the sow to be off her feed during this period.
  • Some sows tend to get extremely restless during oestrus and if not housed in a well-constructed pen, will break out in an attempt to reach the boar.
  • Previous mention has been made of the sow ‘standing’ and she will accept what is called a ‘riding’ test; both of these mean that when pressure is applied to the sow’s back she will stand quite still and as a rule arch her back as if accepting the weight of the boar.

The period of peak ovulation begins about 36 hours after the beginning of oestrus and it is important not to serve the sow too soon. The best system is to serve the sow 12 hours after she will stand for the boar, and gives her a second service 12 hours later. It is important to watch the boar and sow during service to make sure that she has been served properly, and after the first service remove the sow to a nearby pen, where she can be alone until the second service 12 hours later. Even after the second service it is a good idea to keep the sow in a single pen for 2 – 3 days to give her time to settle down, before putting her into a pen or paddock with other dry sows or into a sow stall.


Once the sow has been served, her meal should be reduced from 3,6 kg a day to 2 – 2,5 kg depending on her condition. During the last 3 weeks of pregnancy the meal should be increased to 2,5 – 5,5 kg depending on the size of the sow. As a guide, a sow should gain 10 – 15 kg in weight between each litter, at least for her first 3 – 4 litters. The following table is a guide for feeding dry sows under different conditions:

Good environment, individual feeding2 – 2 ½ kg (4 – 5lb) per day
Good environment, group feeding2 ½ – 3 kg (5 – 6lb) per day
Poor environment, individual feeding2 ½ – 3 kg (5 – 6lb) per day
Poor environment, group feeding3 – 3 ½ kg (6 – 7lb) per day

With regard to the feed itself, it has now been proved without a doubt that dry sows will perform just as well on a 12 – 13% protein feed as compared to the more traditional 16%. The feed MUST be changed to a 16% protein food before lactation starts. This is a snag on many farms, but on larger farms where the management system allows it, low protein feeding during pregnancy certainly cuts costs.


Once sows have been served, they can be housed under one of the following systems:

Run in groups in paddocks. The paddocks must have a good supply of water and be well fenced. Electric fencing is ideal for use with pigs. Each paddock should have individual sow feeders and shelters against sun and rain.

Run in groups in yards which can have concrete floors that are cleared out each day or a deep litter system of straw or stove bedding. Yards should have individual feeders for the sows to avoid fighting and bullying at feeding time.

Figure 1: Sow stalls which provide an individual stall for each sow – see Lecture 5 on Housing.

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