Pig breeding

Credits:Biovision-Infonet

Choice of Breed

Large white is robust, adaptable and of higher performance than most other breeds. It is preferred by most pig farmers in the tropics. The breed is known worldwide and there are no problems obtaining breeding stock from a variety of sources. It is used for the improvement of other breeds e.g. Landrace.

Duroc – Jersey also has good attributes for both rearing and growth in the tropics. Traditionally Durocs have been use as terminal boars. 

Landrace pigs have been widely used for crossbreeding purposes in the tropics. They do well under close confinement feeding but must be well managed and fed.

Selection of Breeding Gilts

• Gilts selected to have at least 12 teats so as to accommodate a large litter
• Gilts to be selected from sows, which wean 9 -10 or more piglets per litter and are known to be good mothers.
• Select breeding gilts at weaning period, further selection should be done at 5 – 6 months of age.
• Select fast growing weaners. These will likely consume less feed per unit live weight gain and are thus less costly to keep.
• Select gilts which have well developed hams and comparatively light heads.
• The selected gilts should have good body conformation i.e. strong legs, sound feet etc.
• Select gilts from saws that can stand the conditions on the farm (housing, feeding, management).

Selection of Breeding Boars 

It is extremely important to select a good boar since it contributes half the quality of the herd. Areas to consider:

• Boar to have sound feet with good, full hams, uniform curve at the back and of good length.
• Boar to have at least 12 nicely placed rudimentary teats so as to pass on this characteristic.
• Selection to be done before castration i.e. at 4 weeks.

Pure-breeding: mating purebred individuals of the same breed. The progeny has the same genetic makeup. The major objective of pure-breeding is to identify and propagate superior genes for use in commercial production primarily in crossbreeding programs as well as to propagate and identify superior females for maintaining valuable genetic material. Furthermore crossbreeding will not be worthwhile unless superior pure bred individuals are used.

Cross breeding: mating two individuals from different breeds thus introducing into the progeny a gene combination that is different from that existing in either parent or in the breed of either parent. Cross breeding can involve two or more breeds, depending on the desired result. The sole purpose of cross breeding is to take advantage of the observed improvement in performance of the progeny above that of either parent. This is known as hybrid vigour or heterosis.

Out breeding: mating individuals of the same breed but which are less closely related than the average of the breed. There should not be a common ancestor for at least four generation back in the pedigree of the boar and the females with which he is mated. It is a useful mating system in purebred individuals.

In breeding: mating individuals of the same breed but which are more closely related than the average of the breed. This could be between such close individuals as those from the same litter or a boar and his daughter. Inbreeding is rarely practiced because it can cause problems such as a decrease in litter size and increases mortality. Inbred sows are inferior in milking and mothering ability. It delays sexual maturity in gilts and boars. Inbred boars have less sexual libido. Inbred gilts have fewer eggs during oestrus and farrow smaller litters than those out bred.  

Breeding Strategy

Breeding is a complex science that requires skill and knowledge. It also requires thorough record keeping. To achieve genetic improvement the following methods can be used:

• Selection: select the best individuals in the herd for breeding, looking at their performance in various characteristics e.g. litter size, growth rate, feed conversion ratio, disease resistance e.t.c
• Retire: remove the individuals that do not perform well.
• Practice cross-breeding – it has at least two advantages: you can combine animals which have different characteristics, which you like. Secondly, it makes the animal stronger to cross animals which are genetically different (heterosis). 

Practical cross breeding 
As mentioned above crossbreeding has two advantages:

• It exploits heterosis, this occurs when two breeds which are genetically different are crossed.
• Ability to combine two or more individuals that have desirable characteristics.

Management of Breeding Stock

a) Boars 

A boar can start serving when it is above 8 months of age. During the first two months of service, the boar should serve only twice per week. After this it can be used up to six services per week. The boar should be kept in its own pen to avoid fighting. Remember that in organic agriculture, it is not acceptable to keep animals indoor at all times, so boars should also have outdoor access regularly. When mating, transfer the sow to the boar (not vice versa).

• One boar can serve up to 15 sows
• Considerable exercise is necessary to prevent the development of leg weaknesses. This can be ensured in a good outdoor run.
• The boar’s feet should be trimmed regularly as deemed necessary.
• Boars should be washed with soap and water every 4 months, and sprayed for the lice and mange if they show any symptoms of this.
• A high level of hygiene is necessary. It is recommended to keep the walls, and in case of lice or mange, a suitable disinfectant should be used.

b) Gilts/sows 

• Provide enough exercise as some sows will tend to fatten if not exercised. A fat sow takes longer to come in heat. It is also more likely to crush her young piglets.
• First service for gilts should not be until the age of 7 – 8 months and the weight to be 100 – 130 kg, depending on the adult weight of the breed or cross. Sexual maturity occurs as early as 4 – 5 months. Reproductive life of a sow is 4 – 5 years.
• Keep about 3-4 gilts/sows per (outdoor) pen of 9 – 10 square metres (organic pigs should have outdoor run at least) which should be kept clean (change bedding regularly). The pens of sows/gilts should be next to the boars to stimulate them to come on heat.

Breeding Cycle. The normal heat period lasts for 3 – 5 days

Heat signs:

1^st stage: Early heat signs 

• General restlessness
• Vulva turns red and is swollen
• White mucus discharge

2^nd stage: Service period signs

Real Oestrus lasts for 40 – 60 hours

Vulva becomes less red and swollen

Slimy mucus discharge

Tendency to mount and be mounted by others.

The sow or gilt will stand still when pressure is applied to her back (can accept a man’s weight sitting on her. Thus the right stage to send her to the boar).

3rd stage: Post Oestrus-period signs

• The sow/gilt will not stand still when pressure is applied to her back.
• The swelling of the vulva disappears.

The usual length of oestrus cycle is 3 weeks (21 days) but shorter or longer periods may be seen in the range of 18-24 days. 

Serving or insemination

Artificial Insemination (AI)

Artificial insemination is becoming popular in pig breeding. It is not a difficult procedure and, provided the basic guidelines are followed, it can be highly successful. The principles of oestrus detection, timing and frequency of insemination do not differ from those employed when using natural mating. However it is important to ensure that:

• Suitable equipment is used
• Suitable insemination environment
• Proper insemination techniques.
• Well stored and viable semen.

Moment of serving / Insemination 

The length of heat period is very variable among sows/ gilts. Ovulation always takes place when 70% of the length of a heat period has passed. Knowledge of the specific heat period of a particular sow is necessary so as to optimize the moment of insemination/service.
ADVICE: Serve or Inseminate 24 hours before ovulation.

Recommended practices:

Usually only a few of the signs will be seen

• Put the sow with the boar for a short period every day when the heat is expected.
• Always take the sow to the boar. This is less upsetting for him.
• Put the sow and boar together just before feeding.
• Allow the boar to serve twice, with an interval of about 12 hours between services. If the sow doesn’t conceive, she will return on heat in about 3-week’s time.
• 10 days before service, give the sow/gilt 1 – 2 kg of extra feed extra per day. Continue this for one week after service.
• During the last month of pregnancy, give 0.5 kg extra feed per day but decrease this gradually one week before farrowing. Provide plenty of water to help prevent congested gut during farrowing.

Stimulating regular heat

• Remove the sow from the piglets after 6 weeks of age all at once.
• Take the sow to a house with dry sows.
• Put the sow close to a boar, in a way that allows direct contact by hearing, seeing and smelling
• The sow should not be given any feed on the day of weaning.
• The next day feed about 4 kg/day. This is called flushing and should be done for a maximum of 10 days or until the service takes place.
• Put the sows in groups (stress stimulates heat)
• If there are heat problems, change the type of feed for a few days.
• Maintain a good climate; see to it that there is sufficient light in the house. In organic agriculture natural daylight is favoured.
• Sows should not be too fat or too thin when they are served. It is important to keep this in mind when determining the ration during the suckling period.

Sow is in gestation when:

• After 21 days of serving she does not show heat signs.
• If practiced by the local veterinarian, it can be recommended to echo scan the sow to be sure that she is pregnant, 25-35 days after service.

Selling/Retiring

• Sows that are difficult to get in-pig (pregnant) or which only manage to rear small litters should be sold off or kept away from breeding activities.
• Boars which are infertile or moderately infertile should be retired and kept away from breeding activities.

Farrowing and birth management

Expected date of birth

On average pregnancy lasts 115 days after conception (3 months, 3 weeks and 3 days). In gilts the udder begins to develop after two months of pregnancy. In the last 14 days of pregnancy the udder will increase in size. It feels firmer, and the nipples stand out more towards the end of the pregnancy.  

Farrowing preparation measures and birth of piglets 

• Washed with soap and water. It can be considered to wash her with a mild disinfectant, but be aware that it is a disinfectant which is environmentally friendly and acceptable according to the organic principles.
• If there is a problem with parasites, she can be treated at this stage for worms, lice and mange, A good acaricide (cattle dip), which is acceptable and not environmentally damaging, can be sprayed on the sow or gilt to kill the lice and ticks. An ordinary sprayer can be used for spraying, following manufacturer’s instructions for mixing the dip with water. Consult your veterinarian to identify relevant treatments; some medicines may be less suitable for treating highly pregnant animals.
• Immediately after washing she should be put in a farrowing pen of her own. The pen should be disinfected before the pregnant sow is put in. Putting the sow in the farrowing pen a week before the birth will help her get used to the new surroundings. This increases chance of a quiet and smooth farrowing. It makes individual feeding of the sow possible.

• 2 days before farrowing, the sow and the pen should be washed. If relevant, it should be disinfected (again).
• Wash with soap and water and then rinse with a mild disinfectant. Water in which Jik or ordinary bleach has been added can be used as disinfectant.

Signs of farrowing

• Udder enlargement during the last 2 days.
• The udder will start to look much redder. 
• A white or clear fluid can now be extracted from some of the teats. 
• The sow will be livelier, alert, and restless and she may start to bite. 
• She scrapes the floor with her forefeet and sweeps the straw bedding into a corner with her snout to make a nest. 
• In group housing the sow may fight other sows.
• Just before delivery, the udder will swell and the sow will calm down. 
• Before the first piglet is born a bloodstained fluid comes out of the vagina. In gilts the fluid may be released earlier. 
• The sow will usually farrow during the night or evening.

Feeding before farrowing

Reduce the feed given to the sow by one third in the last 3 days. Give maize bran if available to act as a laxative. A laxative encourages bowel movement. On the day of farrowing the sow should not be given her normal food but only laxative food (green leafy material, or maize bran for example) to prevent constipation. Should the dung be too hard; some Epsom salt should be given.

Birth of piglets

The duration of farrowing may last 1-2 hours and could go up 12 hours. A few piglets are born in a short interval after which there is a longer interval. If this interval lasts more than 1-2 hours or the total birth lasts more than 5 hours, then it is considered abnormal.

Piglets are born head first. A piglet usually appears every 15 to 20 minutes. Very small piglets may be born very quickly, one after another. During the birth the piglets are still enclosed in a membrane which will usually break open as they are born. It is quite common that piglets are still attached to the umbilical cord when they are born. This cord can be left, as it usually soon breaks off on its own. 30 minutes or an hour after the birth of the last piglet the sow pushes out the afterbirth. The sow may suck blood from the afterbirth to build up her strength.

There are times when a piglet may be still born (born dead). Older sows have a higher tendency to have still-born piglets. Although there are normally very few complications at birth it is advisable for someone to be present.