Principles of pig production FAQs

Our Principles of Pig Production FAQs is designed to equip the pig industry on the different stages of pig production, from breeding to farrowing. Explore the links below for practical advice.

The following questions have been answered by Adrian Cox and Christina Huelsmann-Diamond from Farm Vets. If you have a question you'd like answered, please email Tony Bayles, AHDB's Pork Knowledge Exchange Relationship manager (North):

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Porcine reproductive and respiratory syndrome (PRRS) is a virus which can affect reproductive performance of sows and gilts.

This can vary from sow to sow, but generally within 10 days pre-farrowing sows should start to show enlarged udders, but you can’t express milk (colostrum) until 24 hours prior to farrowing.

Single-parity herds are less common and are unlikely to be as productive as multi-parity herds long term. The benefit is that following the initial herd set-up, there is no introduction of new animals to the herd and thus less risk of a disease breakdown.

However, it also results in poor-performing sows being retained within the herd or herd size decreasing through culling. Generally, sows do not become profitable in terms of productivity until parity 3, and above parity 5, they no longer produce piglets as well as the younger sows (i.e. they generally have lower litter sizes and often do not rear as many piglets).

Outdoor Small Scale Producer example: Pigs can legally be weaned after 28 days of age. With a veterinary derogation, it is possible to wean the pigs as early as 21 days old, if there is a welfare risk to the sow/gilt and as long as there is adequate specialist accommodation for the piglets to be weaned into.

Measuring backfat in this environment would be difficult. It would be better to select on size, foot condition, udder condition and body condition. Stock needs to be restrained adequately so it is still, and a probe placed in a specific area of the animal’s back to assess backfat levels.

This depends on the individual unit and what they are trying to achieve.

Generally, AI is used to improve the genetic line of the piglets, either for replacement but also for a certain breed of progeny. Therefore, if you are paying for this AI, you want the piglets from these lines, rather than the boars, on the unit. Obviously, if you mix natural mating and AI, you cannot guarantee that you are getting what you are paying for essentially.

To rely solely on natural mating on a unit, a lot of boars would be required and care should be taken that no in-breeding is occurring.

Using natural service to ‘mop up’ returning sows is more common and some units find this helpful. I recommend if this is something you are considering that this is discussed on an individual basis with your vet to ensure you get the best outcome.

Unfortunately, this depends on the individual being trained and their willingness to learn.

I would recommend that, as well as on-farm training, any trainees are signed up to courses, e.g. the stockmanship courses run by AHDB, or potentially your vet may be able to offer specific breeding courses as well.

Breeding closely related stock can be used to select for desired traits (line-breeding) but may also result in non-desired traits developing. This would be classed as in-breeding and if noted would therefore not be advisable. It would be considered poor welfare to breed pigs in this way knowing there is a high risk of these problems.

A dry sow is a sow which is in pig, i.e. a sow which is not lactating but pregnant.

Commercial gilts are generally served for the first time at 7–8 months of age and, as a general rule, they should be around 120–140 kg at that time.

Individual genetic lines from different genetic companies may have slightly different individual recommendations, so it is always good to check with them and your vet.

For ‘rarer’ breeds, mating from about 8 months of age would be acceptable.

Boars tend to be used for breeding from 7–8 months of age, although it is important not to overwork a young boar and so it is often best to allow him to be 10–12 months old before becoming a stock boar on gilts.

On commercial units where boars are used for natural mating, they are normally culled after approximately two years of working life. However, if small enough to avoid injuring sows, there is no upper age that would stop a boar working and the reason to cull him would be dictated by his size, temperament, potential leg issues/arthritis, as well as potentially deteriorating semen manifesting as more returns to sows served by him.

Following service, I would ideally leave animals for five weeks prior to further movement in order to reduce the risks of early pregnancy failure, but if a gilt loads onto a trailer easily and is correctly travelled, there should not be too great a risk of movement the day following service. It is not legal to transport animals late in gestation and this should be considered.

Many things influence farrowing rate, including conception rate. Stockpeople have a direct effect on conception rate generally if using AI – so AI technique, handling around service, etc. all affect farrowing rate. Similarly, handling of sows in the dry sow period, e.g. moving and mixing, may affect stress levels of sows, which can impact upon farrowing rate.


In an ideal world, all piglets would receive creep while in the farrowing area (both indoor and outdoor). Creep is important for gut conditioning and allows for better growth and often less post-weaning scour if fed earlier.

However, creep feeding in farrowing paddocks is sometimes difficult and impractical. In these cases, it is best to weigh up cost (time, labour, effort and likely wastage) vs benefit (mostly seen post-weaning). I would therefore suggest that this is a case-by-case decision.

Overall, creep feeding outdoors is far less common but can be accomplished by placing a small amount of creep within the arc for piglets to eat while the sow herself is out feeding, or even having outdoor creep areas that piglets can access that sows cannot. In a smallholder environment, it is certainly worth considering if it is practical.

The plastic balls on the springs in the picture are fixed to the floor and are a particular pig product sold. These are less common in the UK. Far more commonly for enrichment we see plastic on chains, soft wood on chains, straw and straw briquettes, etc. Obviously, we would not recommend using anything which could cause the pigs to choke.

If the water is already below pH 4 naturally, that is fairly unusual and I would certainly recommend further water testing in that situation, including minerals, etc. to see the potential cause. Any water samples should be analysed by your vet/water specialists.

Seek individual advice in this situation. It would certainly be worth discussing this with your vet, as at these low pH levels, water medications may not work and water treatment with chlorination may not work either.

Although possible, it would require very careful dosing and this would be much safer, easier and more accurate with an acid-resistant Dosatron.

Sow feeding and health during lactation certainly has a large impact on the quality of weaner produced and, as a result, this has an impact on the likely growth and performance in the weaning period. More information about management of sows around lactation can be found in the farrowing session.

Unfortunately, there will be some wastage from these feeders. I recommend using a rubber mat to catch some of the food. Round feeders or long troughs both allow social feeding, which is important for pigs. Ensuring there is enough feeding space is likely to be as important as the type of feeder. Often, long troughs allow for more pigs to feed at once.

Some medications can be given orally, so this could be discussed with your vet. However, particular antibiotics will need to be given IM. If this is necessary, restraint using a snare may be required. Ensuring you are using the right size needle is important, as is using a new needle every time (i.e. no blunt needles).

Little-and-often creep feed in the farrowing house is recommended. Start feeding a small handful in a shallow bowl as of about 5–7 days of age. And then slowly increase the amount of feed until it is ad lib by the time of weaning. Creep needs to be fresh to be palatable.

It has been shown multiple times that the piglet microbiota is affected by the dams through transmission in utero but also during the birth process. I think this puts more importance on ensuring the sows/gilts are adequately managed in the dry sow period, including environmental management, feeding, handling, etc.

Managing the sows during lactation will also be very important as further colonisation takes place at this point. This again includes environment management, as well as handling and nutrition. Further information on feeding sows adequately in these stages can be found throughout the Principles of Pig Production series and I would also recommend speaking to nutritionists on this matter.

Generally, the studies have been transition feeder compared with dry pellets and gruel feeding compared with dry pellets. Transition feeders may present as a less labour-intensive way to dispense gruel feed.

This would depend on system, age at weaning, previous creep feeding and feed type, but assuming a standard ration, around 200 g/per pig/d creep. Realistically, people are achieving around 150 g/per pig/d creep.

Growing and finishing

Ammonia is hard to measure and generally there is very little equipment to accurately measure on farm, so I would say as a crude measurement, if you would not want to be in the shed for a long period of time because of the poor atmosphere, then the ammonia levels are likely to be having a significant effect on the pigs also.

I would say in general dunging is very often related to temperature and presence of draughts. Pigs tend not to lie in a cold and draughty area (this may either be well lit or a dark corner) and this often becomes the dunging area. If things like kennels are used, these are often darker areas of the pen, but pigs are less likely to dung there due to the lids keeping the areas warm.

I would definitely recommend ventilation is checked regularly regardless. I would hope the basic functioning would be checked daily. Particularly in ACNV-type sheds where the inlet flaps often can get caught and they may be open different amounts within the same shed, this needs to be seen and rectified before problems materialise ideally. Ventilation should be serviced professionally at the very least yearly if it is automated.

The Welfare Codes do not stipulate light colour exactly. Generally, we would be seeing white light being used in sheds in the form of LED bulbs. There must be some respite from artificial light for pigs.

Light levels and ammonia levels need to be measured if incidences of vice are seen on farm, according to the welfare codes.

Principles of pig production Webinars

Catch-up on our four-part series with Adrian Cox and Christina Huelsmann-Diamond from Farm Vets, focusing on the different stages of pork production. It’s designed to refresh or provide new entrants with an overview of the breeding, weaning, finishing, growing and farrowing process.