Batch farrowing

Considerable advantages can be gained through the use of all-in all-out pig management systems, even within herds of minimal disease status. A key to this strategy, in which groups of similarly aged pigs are protected from contact with older groups throughout their weaning to market period, is the establishment of a batch farrowing system. Instead of sows continually entering and leaving the farrowing room individually, they arrive together to fill an empty farrowing room, farrow within a day or two of each other and leave together after weaning; ready for the room and crates to be cleaned thoroughly before the next group arrives to use the pens.


More efficient use of time and improved pig management may be achieved by dividing your breeding females into groups, each group being large enough to fill the farrowing accommodation, and then synchronising the farrowing within each group. Incorporating an all-in all-out system with batch farrowing has been proven to result in lifetime growth rate increases of 100 g per day and more.


It is not necessary to run a batch farrowing herd as an all-in all-out operation between weaning and marketing, but to do so would help maximise the advantages of both technologies.

Batch farrowing systems will not suit all producers and are probably more suited to the smaller family run herd of 300 sows or less, where time between the busy weeks could be spent with family or working on other enterprises.

It is a system well suited to operating cooperative ventures between producers. For example, three producers may decide that one of their farms should be converted to a batch farrowing unit, another could become a weaner unit, and the third would serve as a grower or finisher unit. This arrangement produces the health benefits and management efficiencies of all-in all-out and multi-siting.

Alternatively, four producers, each with 45 farrowing crates and using the four-week cycle (i.e. weaning at three weeks), could supply a common grow-out site with a month's supply of weaners every week. In effect, the four producers would produce the output of a 1000-sow herd.

Batch farrowing allows you to limit the number of times the pigs are moved, which reduces growth setbacks associated with stress and fighting. Ideally, pigs would only move twice at most; once from the farrowing house into weaner accommodation, and once more into finisher accommodation. If you are worried that weaners going into finisher pens will be too cold during the cooler months, leave some pens empty and raise density in others for a fortnight or so. When the weather permits, weaners should occupy finisher pens or shelters at the stocking rate recommended for their final liveweight (example 0.66 m² per 100 kg pig).

Batch farrowing is also the best way to produce pigs for deep-litter systems, where a group of up to several hundred pigs of equal age might spend its entire growing and finishing period together.


  1. Ideal for the all-in all-out pig management system, which is known to reduce the effects of production-limiting diseases and increase growth rates.
  2. Management of breeders, weaners, porkers and finishers in groups results in more efficient use of time (e.g. pregnancy testing, litterwork), materials (e.g. iron dextrose, vaccines, withholding period medications) and feed.
  3. Room environments can be finetuned to suit particular age groups without disadvantaging older or younger pigs.
  4. With pigs managed in distinct age ranges, you can progressively adjust diets through the grower/finisher period (phase feeding), knowing that feed can be specifically formulated for entire grower/finisher populations. This also eliminates the need to have all grower-herd diets stored and available at all times, as is the case in continuous-flow herds.
  5. Pig movements and management practices can be more easily planned and predicted. Busy and slow periods can be plotted months in advance.
  6. Mating targets are more efficiently met. For example, if there are 24 crates to be filled, the producer may be reasonably confident that 28 good matings in the monthly mating week will meet the pregnancy target, leaving four females to be culled or held over each month. In a continuous 24-crate system, six crates must be filled every week, and assuming comparible fertility to the batching herd, at least eight matings will take place every week, producing a minimum of eight culls or held over females each month.
  7. There is more incentive to meet mating targets as failed matings result in empty crates. These daily reminders of inefficiency are more easily hidden in a continuous-flow system, in which a sow with a low-weight litter can be left in a crate for an extra week or two.
  8. In a system where matings are concentrated into a set period, such as one week per month, artificial insemination (AI) is highly appropriate. Not only will AI introduce genetic improvement and safeguard herd health, it is generally quicker than natural mating and grouping the inseminations together will reduce freight costs for semen transport. A further saving can be made through the reduction of boar numbers, although keeping a few boars around to stimulate oestrus is always advisable.
  9. It is possible to market larger groups of uniform animals. In the US this has enabled producers to secure better prices and reduce contract freight costs.
  10. Even where all-in all-out systems are used, it is possible to selectively market finishers over a few weeks. For example, if a group of pigs enter a finishing room for an eight-week period, the 'top' pigs will be ready to go in about six weeks, followed by the 'middles' a week later, and then all others would go to market the next week, leaving the room ready for cleaning and re-use.
  11. Cross fostering is easier, with more foster mothers to choose from, especially when colostrum is needed.
  12. Busy weeks (mating, farrowing, weaning and cleaning) alternate with less active times (feeding and marketing), allowing more economical use of casual labour and better management of time.
  13. Being able to spend more time in the farrowing room should result in earlier detection of problems such as blocked feeders and drinkers, sick sows, trapped or wounded piglets, or farrowing problems etc.
  14. Regularly emptied facilities can be more thoroughly cleaned and maintained.


  1. Gilts and 'stale' sows can fail to cycle within the required period, meaning that extra females need to be mated to avoid empty crates. This could lead to an oversupply of pregnant females.
  2. If you choose not to use AI, boar demand would alternate between heavy and light.
  3. Late farrowing or small piglets cannot be held back for extra time on the sow as their farrowing pen is required for the next batch.
  4. Unpredictably late and early farrowing within a group will extend the age and weight ranges of weaner groups.
  5. Workload is particularly heavy for one week per batch, when weaning is closely followed by cleaning, disinfecting, filling crates, new farrowings, litterwork and heat detection and matings of the most recently weaned sows.

Number of batches

This depends almost entirely on litter age at weaning, which largely determines the interval between successive farrowing groups within the same farrowing pens. The most common farrowing interval is 28 days, which includes a 21 to 22-day lactation period, followed by a week during which the farrowing house is emptied and thoroughly cleaned and the next group of females is brought in a few days prior to farrowing. A 28-day lactation would result in a five-week interval between the farrowings of each batch.

Lactation 21 days, farrowing interval 20 weeks

A 28-day batching period is achieved by weaning at around 21 days. If the average weaned sow is mated five days after weaning, and has a 114-day pregnancy, she will farrow 140 days, or 20 weeks after her previous litter was born. This 20-week cycle requires five groups of sows, as seen in Figure 1. Group 1 sows are ready to farrow their second litters four weeks after the first farrowing of Group 5, which fits precisely with the 28-day turnaround period of a three-week lactation followed by one week to clean the room and settle in the next group.

Figure 1: 28-day farrowing turnaround.

An irregularity will occur with a 35-day farrowing pen turnaround, with an extra week appearing in the system after every four farrowing groups. This extra week is shown in Figure 2.

Lactation 28 days, farrowing interval 21 weeks

Figure 2: 35-day farrowing turnaround.

The longer lactation means that only four groups can share the farrowing pens as if there was a fifth group it would farrow just one week before Group 1 is ready to farrow again. It can be seen that the second farrowing of Group 1 (week 21) is six weeks after the first farrowing of Group 4 (week 15), instead of the usual five weeks (four-week lactation and one-week clean and preparation) between the other farrowing groups. This extra week comes along every 20 weeks.

A great advantage of having this spare week is the opportunity it gives to schedule holidays or maintenance. Fixing building structures or fittings can be done without pigs present. The spare week progressively 'moves' from farrowing to market, following the most recent batch of pigs through, enabling maintenance to be scheduled for all production areas.

Number of females in the herd

Each group would contain enough sows and gilts to fill the farrowing accommodation, with an appropriate buffer to allow for returns to service, or unexpected culls. Multiply the number of groups by the number of pens, add a buffer of around 10% and you have your number of female breeders.

However, before deciding the size of the female inventory, the producer must identify the area most likely to limit, or 'bottleneck' the farm's animal movement. For example, you shouldn't use every farrowing pen if your weaner (or grower or finisher) accommodation is not big enough for a full month's worth of weaners (or growers or finishers) arriving at once.

When considering the move to batch farrowing, it is useful to draw a simple pig-flow diagram such as the one below, in order to recognise any physical limitation imposed by your accommodation. This is particularly important if the herd is moving to an all-in all-out system.

Figure 3: Example of a pig-flow diagram.

In the above example, two weaner rooms are filled alternately every four weeks, to ensure that each batch has eight weeks of growth without other batches entering or leaving the same room. After the eight weeks, the batch is transferred to one of three rooms or shelters for their remaining 12 weeks.

Where separate rooms, sheds or shelters are unavailable, partition the area to create separate air spaces; this has proven to be of benefit to health and growth rates.

Getting them cycling together

Initially, each group of females must be carefully managed to ensure synchronous farrowing. This can be achieved in several ways, some of which will involve your veterinarian:

  1. Prostaglandin hormone injections between 10 and 35 days after mating will cause pregnant pigs to resorb their embryos and return to service three to five days later. If the gilts and non-lactating sows needed to form a group have been mated at least 10 days, they can be injected with prostaglandins at the same time the group's lactating sows are weaned, resulting in a uniform return to oestrus across the whole group. Careful use of prostaglandins can also induce farrowing two to three days early, helping to shorten the time range of a batch farrowing, as well as helping to avoid weekend farrowing. It should be noted that pregnant women, women of child-bearing age and people with asthmatic conditions should not handle these products.
  2. You could progressively wean sows together, over a range of litter ages. For example, if you normally wean at four weeks, the first weaning would involve all litters between the ages of three and five weeks. This means that a fortnight's weaning is done on the same day. It follows that a month's weaning result in two batches of breeder females cycling a fortnight apart. Once pregnant, they will then farrow two weeks apart, but be weaned together when the earlier group of litters is five weeks old and the later group is three weeks old. You now have a full month's females cycling together, and when all your females have had their second litters weaned, you have achieved the grouping of your females with the aim of filling your pens once a month. (See diagram below.)
  3. If weaned females are allowed to cycle but are not mated, prostaglandins can be used to advance the cycling of the more recently weaned sows, although the cycle appears to reduce by only five days or so.
  4. The simplest way to synchronise is by using a commercially available progesterone hormone (injected or in feed), which delays the onset of oestrus in weaned sows. When enough females have been weaned, hormone treatment can be stopped, and within five to six days around 65% of them should have returned to oestrus, with up to 90% returning within 10 days. This method is also the best way to synchronise incoming gilts with the sows they are destined to join.

Figure 4: Weaning two weeks of sows together at one weaning and again at the next, produces one batch.

When to wean

The farrowing interval should allow for how much time you can devote to piggery operations. The longer the lactation period, the greater the interval between the busy one-week periods that involve weaning, cleaning, oestrus detections/mating and new farrowing. A three-week lactation would suit producers dedicating most or all of their time to a piggery operation, while a four week or later lactation would better satisfy the producer who has other enterprises to run apart from the piggery, or who just prefers to wean at a heavier weight.

Weaning on Thursdays will generally result in re-mating on Monday or Tuesday of the next week, with most of the resultant farrowing taking place between a Tuesday and the following Thursday. This allows weaning to take place on a Thursday a number of weeks later.