Sow mortality has been an increasing issue in pig production. Pelvic organ prolapses (POP) are one component of sow mortality and can include vaginal, uterine, rectal, or combinations of prolapse. The incidence of POP has increased in the USA since 2015. Pittman (2017) reported the annual average removal reason due to prolapse as 6% from 2013 to 2016, with an increase to 12% from 2016 to 2019. Ross (2017) summarized multiple factors on the farm level and individual sow level that could affect the incidence of POP. Ross identified four potential risk factors for prolapse incidence: water treatment and bump feeding strategies on the farm level, and perineal score and body condition on the sow level. Genetic factors have also been proposed. Unfortunately, there is less information available on the genetic parameters of prolapse. What little genetic data that has been available has been collected for purebred sows from a relatively small number of purebred herds located in the USA. The levels of heritability for POP appear to be quite low.
These U.S. researchers wanted to investigate genetic parameters for sow pelvic organ prolapse in both purebred and crossbred herds. Purebred prolapse and crossbred prolapse were considered two separate traits for analysis. Pelvic organ prolapse was recorded as normal or prolapsed on the individual sow level across 25 purebred and 8 crossbred farms located in both North and South America. Some Canadian herds were included in the data. In total, 18,415 purebred Landrace sows from a single maternal line were recorded between 2013 and 2016. Prolapse data from 43,838 commercial two-way crossbred Landrace × Large White sows was collected between 2015 and 2016. There were 204,513 animals included in the total pedigree.
The researchers found the following:
- The average POP incidence rate for purebred sows was 3.13%.
- The average POP incidence rate for commercial crossbred sows was 6.56%.
- Estimates of heritability in the observed scale were 0.13 (±0.03) for purebreds and 0.14 (±0.01) for crossbreds.
Take-Home Messages
- The researchers suggested that including data from both purebred and crossbred herds is helpful in genetic selection processes aimed at reducing the incidence of prolapse.
- The researchers further suggest that in the battle to reduce the incidence of prolapse, it will take a great effort to pull together the databases that are needed to shed light on genetic heritability. Reducing prolapse incidence rate can be achieved to some extent through genetic improvement, but it is most likely that the most effective gains will come by addressing sow management factors.
