How to Reduce Piglet Mortality in the Farrowing Unit
The productivity of a pig herd is measured in terms of pigs (or kg) produced per sow per year. Piglet mortality saps your farm’s productivity right from the start. Furthermore, mortality in the farrowing unit remains the highest in the industry, compared to other stages. Pre-weaning mortality in piglets ranges from 10% to 20%, whereas it is 2.5% in the finishing stages (Muns et al., 2016).
Even small reductions in piglet mortality translate into significant productivity improvements later on. In this article, we will take an in-depth look at how to prevent piglet mortality, starting with its causes, general measures to avoid it, and specific prevention strategies.
Read also: How to minimise Piglet Stress
Causes of mortality in piglets
In the womb, piglets are protected from a hostile environment; not even the best-designed farrowing pen can compete with the comforts of prenatal life. After farrowing, piglets need to adapt to completely new circumstances: temperature, suckling, competing with littermates, and a host of pathogens that attack their immature immune systems.
Learn MoreFailure to adapt quickly leads to death. With so many pressures, piglets usually die not from a single factor, but from a combination of causes. A subtle cause usually leads to a more evident one; for example, chilling leads to crushing. This is an important point because it is natural to want to address a visible cause while neglecting the underlying ones. However, piglet mortality should be understood as a whole.
Causes of pre-weaning mortality from necropsy findings (adapted from Vaillancourt et al., 1990).
Sow crushing
By far, the most important, non-infectious cause of piglet mortality is sow crushing. Crushing occurs when the sow changes position. The most important sow behaviour that leads to crushing is rolling, followed by sit-to-lie and stand-to-lie repositioning. Crushing can also occur when a sow steps on a piglet and savaging has also been reported (Nicolaisen et al., 2019; Muns et al., 2016).
Maternal ability is an important sow factor in crushing. Because sows crush their piglets consistently over farrowing (Jarvis et al., 2005), records should be kept to inform culling and breeding decisions.
Piglet factors also influence crushing. In normal circumstances, piglets simply get out of the way of the sow. However, piglets that are failing to adapt will likely be torpid due to hypothermia, starvation, and lack of energy. Crushing is the result of a complex chain of events.
The environment also plays a role in crushing. The most obvious factor is the housing system. It is a well-established fact that farrowing crates that restrict the sows’ movements significantly reduce crushing when compared to loose and group housing, and free-ranging (Hales et al., 2014). Nevertheless, sow crates have been one of the most controversial topics of debate in the pig industry. As sow welfare and ethical concerns come to the forefront, there is a push toward less restrictive housing systems. Nicolaisen et al., (2019) recently observed that most crushing deaths occur during the first 3 days post-farrowing.
Coccidiosis and scours
Within the infectious causes of pre-weaning piglet mortality, scours are by far the most significant. Piglet scours can be caused by viruses, bacteria, parasites, or a combination of the three.
Rotavirus is practically ubiquitous in pig farming. However, it has low mortality. On the other hand, Transmissible Gastroenteritis (TGE) and Porcine Epidemic Diarrhoea (PED) can devastate a farm. TGE can cause 100% mortality in piglets from naïve herds!
The most significant bacteria that cause scours in the farrowing unit are Escherichia coli and clostridia. E. coli, the causative agent of colibacillosis, is probably the most common cause of scour in piglets. If treated, mortality is low, otherwise, it quickly leads to dehydration and death. Clostridiasis has a very high mortality rate; however, infections usually happen when there is poor management.
Coccidia (Isospora suis) is probably the most economically significant pathogen of piglets. It causes scour and usually has low mortality. Nevertheless, it leads to significant losses throughout the production process and, because it damages the gut lining, leaves the door open for the deadly clostridia.
Coinfections are quite common. We have already mentioned how coccidia and clostridia can help each other aggravate disease. Another common pathogen association is that of viruses and E. coli.
Neonatal diarrhoeas (scours) affect piglets at different times. To assist in diagnosis, it is crucial to know the timing of the scour and also develop an eye for the characteristics of the diarrhoea. We take a deep dive into piglet scours in this article.
Passive immunity transfer failure
Because of the type of placenta that pigs have, sows cannot transfer antibodies to their piglets while they are in the womb. Therefore, piglets are born into a hostile environment… without any defences against deadly pathogens! To overcome this vulnerability, sows produce colostrum, a special ‘milk’ that is packed with antibodies and energy. During their first 24 to 48 hours of life, piglets’ guts are permeable to immunoglobulins: the antibodies they drink can pass into the bloodstream. This is called passive immunity transfer.
However, piglets’ capacity to absorb antibodies quickly declines after the first 6 hours of life! If piglets don’t drink enough colostrum as soon as possible, they will not have immunity and, most likely, will readily succumb to all and any pathogens. This is called ‘passive immunity transfer failure’.
Colostrum intake depends on the ability of the sow to produce high-quality colostrum, but also on the piglets’ capacity to compete for a teat, suckle, ingest and absorb it. Declerck et al. (2017) conducted a large study to determine which factors most influence colostrum intake in individual piglets; some of the most significant are oxytocin use, large litters, and body weight within the litter. Some factors, such as stillborn piglets, also influence the variation of colostrum intake among littermates —which increases the risk of passive immunity failure for the lighter, weaker piglets.
Low viability
Some piglets are born underweight, weak, and have a low chance of survival if no measures are taken. In the past, there was a cut-off of around 900 g bodyweight at birth to classify underweight piglets. However, we have learned that viability is a more subtle concept, because it is also relative: an 850 g piglet might fare better around similar-sized littermates than a 1,200 g runt in a very heavy litter.
Weight at birth is not the only factor that influences viability. For example, placental infarction, umbilical cord rupture, and poor sow nutrition lead to less viable piglets. Sow prolificacy (the main genetic trait influencing litter size) has been one of the major breeding objectives in the industry. This has led to the unintended consequence of less space in the womb for all the piglets, which can cause a higher rate of unviable piglets (Tucker et al, 2021).
Dystocia, or difficulty during farrowing, can lead to asphyxia, hypoxia, brain damage, bleeding, and trauma, resulting in less viable piglets. The same could be said for longer farrowing.
Another important aspect of modern pigs is that, because of their fast growth rate, they quickly outrun their iron supplies and develop anaemia, which also leads to weakness and low viability.
Low viability also puts piglets at a much greater risk of crushing.
Deformity
We should consider deformity as a subset of low viability. The most common deformity in newborn piglets is splayleg. Splay-legged piglets have low muscle tone or development so they cannot keep their legs upright. Because splaylegs cannot get away from the sow, they are very prone to death by crushing. This condition affects the hindlimbs, the forelimbs, or both (also known as ‘stars’, with an extremely low survival rate).
Most deformities, such as atresia ani (absence of anus), cardiac abnormalities, and extreme teratogenic events are fatal and result in death during the first hours or, at most, days. Others, such as hernias, could be corrected surgically, depending on the severity of the problem.
Deformities can be caused by genetic, infectious, and chemical factors (such as toxins or medicines). These problems tend to be sporadic, so, if they are becoming common on a farm, there should be a thorough investigation to determine and correct the cause.
Starvation and exposure (chilling)
Neonatal piglets prefer a temperature of 35 °C. However, this is just too hot for sows, most comfortable between 15-20 °C. Piglets with lower core temperature quickly become lethargic, so they nurse less; consequently, they have less energy to move and to keep their temperature up, leading to less activity and less willingness or ability to nurse. This is a vicious cycle that can cause death on its own or lead to crushing.
Pigs are especially susceptible to chilling because of their characteristics at birth. Their high surface-to-volume ratio means they lose heat quite fast (Tucket et al., 2021). Because they are born wet, they can quickly become hypothermic if there are drafts in the farrowing unit. Furthermore, unlike other mammals, pigs don’t have brown fat, which helps juveniles from other species maintain their body temperature, even in adverse conditions.
Agalactia
When sows fail to produce colostrum or milk, piglet mortality increases dramatically. Agalactia can result from infections, such as the Porcine Respiratory and Reproductive Syndrome (PRRS), caused by a virus.
However, agalactia is often bacterial in origin, and it rarely comes alone. Therefore, veterinarians speak of a post-partum syndrome that includes metritis (infection of the womb), mastitis (infection of the mammary glands), and dysgalactia (reduced or absent milk production). The most common term today is Post-partum Dysgalactia Syndrome (PDS), but you may also know it as lactation failure, agalactia complex, or postpartum agalactia (Kemper, 2020).
Sow malnutrition and poor body condition can also lead to agalactia.
Read also: Organic Diet for Organic Pigs and Poultry
Creating the right farrowing environment
As we have seen so far, the causes of piglet mortality are many and they interact in complex ways. Therefore, focusing all your energy on just one apparent cause is usually not the best long-term strategy. The best way to reduce piglet mortality rate is to create the right farrowing environment. Favourable conditions will eliminate most of the specific causes and, should a problem arise, it will be easy to detect and root out.
The first step to create a good farrowing environment is to keep an open mind and not overlook the obvious. A simple walk around the farm, with a critical eye, will reveal the major areas of opportunity: do we have a drafty farrowing pen? Are there rodents or other vermin present on the premises? Did we formulate a diet for the sows? Are the farrowing crates clean?
Spending a few minutes drawing a diagram of the complete production process is also a useful exercise. This will reveal some of the most impactful mistakes: are we mixing age groups? Are we skipping the gilt quarantine period? Are we skipping the gilt acclimation period? Are we weaning too early or too late? Are we cross-fostering too much or not enough?
The next step is to create a checklist for the farrowing unit. Even though it is an integral part of the farm, the farrowing unit should be managed as an almost separate entity. Because even small mistakes during farrowing will have a big impact on herd productivity, it is important to have a farm policy and to have a systematic approach to management.
We have created a guide that will take you step by step in the creation of a checklist for your farrowing area, from gilt selection all the way to stockmanship.
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