Why do sows habitually crush their piglets to death?
Some sows habitually crush their piglets to death
(Agricultural Wealth Network) Translated by Chen Fusheng from Pig Progress 2002, Vol.18, No.13
Research shows that some sows habitually cause the death of their own piglets. This information helps us formulate culling strategies and suggests that we can improve sow mothering ability through genetic selection.
Pre-weaning piglet mortality has always been one of the important causes of economic loss in the pig industry, and picking up dead piglets is also distressing for any stockperson. The types of mortality also vary greatly among different rearing systems: in loose-housing and outdoor rearing systems, crushing is more serious; for sows kept in farrowing crates, stillbirth and sow savagery are more serious.
The relatively high mortality rates in many loose-housing systems show that many pig farms have been struggling with this. In one production system, it is common to see some sows perform well while others perform terribly. For example, in a small study observing 46 gilts farrowing in pens, three-quarters of piglet deaths (mainly crushing) occurred in only one-third of the sows. We wanted to find out whether the extremely poor mothering performance of some gilts could be a characteristic of a sow, so that the sow would continue to repeat this behaviour in the future.
To find out whether a sow's piglet mortality situation remains the same in subsequent litters, we analysed the production records of a commercial pig farm over 11
years. The farm used farrowing crates for farrowing sows, and we analysed the records of 125 Large White x Landrace sows from parities four to nine. For each litter, we determined the number of live-born piglets and stillborn piglets (excluding mummified piglets) as well as the total weight of live-born piglets. For pre-weaning deaths, the date of death and cause of death were analysed.
The results presented a depressing and familiar picture. In our statistics, 6.5% of piglets were stillborn, and another 14.3% died before weaning. These deaths were mainly due to crushing (6.8
%) and low viability or starvation (4.4%). Savagery was relatively rare in our analysis (<0.2%), but this may be because savage gilts are often culled and therefore do not reach parity four.
Risk factors
Our analysis focused on the three main causes of death (stillbirth, crushing, low viability/starvation), and also analysed the total number of live-born piglet deaths (regardless of cause). The risks of death from all four causes were greater in large litters and in litters with relatively low birth weights. Large litters have a longer farrowing process, which more easily causes piglet hypoxia and leads to stillbirth. Competition for teats increases the nutritional stress of piglets in large litters, thereby increasing the possibility of starvation, and lighter, starving piglets will stay near the udder for longer periods, so when the sow lies down they face a greater risk of being crushed and lack the strength to escape.
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Most types of mortality increase with parity (Figure 1). Older sows have more stillbirths, possibly because weakened uterine muscles prolong farrowing. Deaths from any cause among live-born piglets also increase with parity. Crushing in particular increases with parity, and there may be multiple reasons for this. As the sow's body and age increase, her agility and her ability to respond to the screams of crushed piglets may decline, so the incidence of crushing events increases. A sow's responsiveness to piglets declines with age and experience. Unexpectedly, deaths due to low viability/starvation were not affected by parity, even though older sows have relatively lower milk production.
Figure 1 The mortality rate of live-born piglets as well as the incidence of stillbirth and crushing all increase with parity, and deaths due to low viability and starvation show the same trend (figure omitted)
Overall, this analysis of mortality risk factors shows that selecting for live-born litter size at the expense of piglet birth weight increases the risk of pre-weaning piglet mortality.
Sow consistency
After taking into account the various factors affecting piglet mortality, the situation remains that some sows cause a large number of piglet deaths. For the same sow across her parities, the risks of stillbirth and crushing of her piglets are consistent, and the overall risk of piglet death after birth (death from any cause) is also fairly consistent to a certain extent across parities. For the same sow, stillbirth and crushing across her parities are highly repeatable. This may not be surprising, because this is likely directly related to the sow's reproductive physiology and anatomy (stillbirth), and also directly related to the sow's maternal behaviour (that is, crushing, although piglet viability and behaviour also play a role). In some sows, piglet deaths caused by low viability are not consistent across parities. Differences caused by different boar genotypes may be one of the reasons for this phenomenon.
Is it a genetic trait?
The measured repeatability values correspond to those of other reproductive traits, indicating that selection for low piglet mortality is possible, but larger genetic studies are still needed for this. However, what is encouraging is that the huge differences among individuals in this study indicate that if these traits are heritable, genetic progress is very likely to be achieved. Looking at the various causes of death, the best sows in this study never caused piglet deaths from this cause throughout their entire reproductive career. On the other hand, there are also "terrible" sows; for example, one sow lost 45.8
% of her live-born piglets to various causes during her lifetime, while another sow crushed 30.8% of the piglets she produced.
For pig producers, the consistency of a sow's performance across her parities means it is necessary to check her piglet mortality records when deciding which sow to cull (or when deciding which sow to mate). Further research is needed to determine whether sow traits affecting piglet mortality can be improved through genetic selection. In the past, breeding companies have succeeded by increasing live-born litter size. Selecting for good mothering ability may be another feasible approach, which can be used to increase the number of weaned piglets without increasing mortality, so as not to harm pig welfare or the evaluation of stockpersons.
In our study, the protection of farrowing crates very likely masked the differences in piglet crushing rates that sows would otherwise have shown under loose-housing conditions, because under such conditions sows' freedom to express their good or poor mothering ability is restricted. Nevertheless, we still found differences among individual sows in piglet crushing rates under loose-housing conditions, and differences in piglet crushing rates under loose-housing or outdoor rearing conditions. Under loose-housing or outdoor rearing conditions, selecting for individuals or genotypes with good mothering ability is likely to be even more important.
Original title: Sow consistency in crushing mortality (English) Original authors: Dr. Rick D'Eath and Dr. Susan
Jarvis (SCA, UK)
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Thanks for sharing, bumping this
--------------------------------------
Thanks for sharing, bumping this
Research shows that some sows habitually cause the death of their own piglets. This information helps us formulate culling strategies and suggests that we can improve sow mothering ability through genetic selection.
Pre-weaning piglet mortality has always been one of the important causes of economic loss in the pig industry, and picking up dead piglets is also distressing for any stockperson. The types of mortality also vary greatly among different rearing systems: in loose-housing and outdoor rearing systems, crushing is more serious; for sows kept in farrowing crates, stillbirth and sow savagery are more serious.
The relatively high mortality rates in many loose-housing systems show that many pig farms have been struggling with this. In one production system, it is common to see some sows perform well while others perform terribly. For example, in a small study observing 46 gilts farrowing in pens, three-quarters of piglet deaths (mainly crushing) occurred in only one-third of the sows. We wanted to find out whether the extremely poor mothering performance of some gilts could be a characteristic of a sow, so that the sow would continue to repeat this behaviour in the future.
To find out whether a sow's piglet mortality situation remains the same in subsequent litters, we analysed the production records of a commercial pig farm over 11
years. The farm used farrowing crates for farrowing sows, and we analysed the records of 125 Large White x Landrace sows from parities four to nine. For each litter, we determined the number of live-born piglets and stillborn piglets (excluding mummified piglets) as well as the total weight of live-born piglets. For pre-weaning deaths, the date of death and cause of death were analysed.
The results presented a depressing and familiar picture. In our statistics, 6.5% of piglets were stillborn, and another 14.3% died before weaning. These deaths were mainly due to crushing (6.8
%) and low viability or starvation (4.4%). Savagery was relatively rare in our analysis (<0.2%), but this may be because savage gilts are often culled and therefore do not reach parity four.
Risk factors
Our analysis focused on the three main causes of death (stillbirth, crushing, low viability/starvation), and also analysed the total number of live-born piglet deaths (regardless of cause). The risks of death from all four causes were greater in large litters and in litters with relatively low birth weights. Large litters have a longer farrowing process, which more easily causes piglet hypoxia and leads to stillbirth. Competition for teats increases the nutritional stress of piglets in large litters, thereby increasing the possibility of starvation, and lighter, starving piglets will stay near the udder for longer periods, so when the sow lies down they face a greater risk of being crushed and lack the strength to escape.
--------------------------------------
Most types of mortality increase with parity (Figure 1). Older sows have more stillbirths, possibly because weakened uterine muscles prolong farrowing. Deaths from any cause among live-born piglets also increase with parity. Crushing in particular increases with parity, and there may be multiple reasons for this. As the sow's body and age increase, her agility and her ability to respond to the screams of crushed piglets may decline, so the incidence of crushing events increases. A sow's responsiveness to piglets declines with age and experience. Unexpectedly, deaths due to low viability/starvation were not affected by parity, even though older sows have relatively lower milk production.
Figure 1 The mortality rate of live-born piglets as well as the incidence of stillbirth and crushing all increase with parity, and deaths due to low viability and starvation show the same trend (figure omitted)
Overall, this analysis of mortality risk factors shows that selecting for live-born litter size at the expense of piglet birth weight increases the risk of pre-weaning piglet mortality.
Sow consistency
After taking into account the various factors affecting piglet mortality, the situation remains that some sows cause a large number of piglet deaths. For the same sow across her parities, the risks of stillbirth and crushing of her piglets are consistent, and the overall risk of piglet death after birth (death from any cause) is also fairly consistent to a certain extent across parities. For the same sow, stillbirth and crushing across her parities are highly repeatable. This may not be surprising, because this is likely directly related to the sow's reproductive physiology and anatomy (stillbirth), and also directly related to the sow's maternal behaviour (that is, crushing, although piglet viability and behaviour also play a role). In some sows, piglet deaths caused by low viability are not consistent across parities. Differences caused by different boar genotypes may be one of the reasons for this phenomenon.
Is it a genetic trait?
The measured repeatability values correspond to those of other reproductive traits, indicating that selection for low piglet mortality is possible, but larger genetic studies are still needed for this. However, what is encouraging is that the huge differences among individuals in this study indicate that if these traits are heritable, genetic progress is very likely to be achieved. Looking at the various causes of death, the best sows in this study never caused piglet deaths from this cause throughout their entire reproductive career. On the other hand, there are also "terrible" sows; for example, one sow lost 45.8
% of her live-born piglets to various causes during her lifetime, while another sow crushed 30.8% of the piglets she produced.
For pig producers, the consistency of a sow's performance across her parities means it is necessary to check her piglet mortality records when deciding which sow to cull (or when deciding which sow to mate). Further research is needed to determine whether sow traits affecting piglet mortality can be improved through genetic selection. In the past, breeding companies have succeeded by increasing live-born litter size. Selecting for good mothering ability may be another feasible approach, which can be used to increase the number of weaned piglets without increasing mortality, so as not to harm pig welfare or the evaluation of stockpersons.
In our study, the protection of farrowing crates very likely masked the differences in piglet crushing rates that sows would otherwise have shown under loose-housing conditions, because under such conditions sows' freedom to express their good or poor mothering ability is restricted. Nevertheless, we still found differences among individual sows in piglet crushing rates under loose-housing conditions, and differences in piglet crushing rates under loose-housing or outdoor rearing conditions. Under loose-housing or outdoor rearing conditions, selecting for individuals or genotypes with good mothering ability is likely to be even more important.
Original title: Sow consistency in crushing mortality (English) Original authors: Dr. Rick D'Eath and Dr. Susan
Jarvis (SCA, UK)
--------------------------------------
Thanks for sharing, bumping this
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Thanks for sharing, bumping this