Sow mortality can cause significant animal welfare and economic costs on Canadian farms.
As well, the loss of a productive sow brings significant opportunity costs. If we consider the loss of a pregnant sow, when you include the replacement cost of a gilt, investment in annual vaccinations, lost opportunity in the piglet litter that will not be sold and the lost opportunity to sell the cull sow, the cost to the farm is more than $1,400 per sow.
Another less obvious and more practical economic impact is the cost of carcass removal, compost or burial.
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On some large sow farms, it is not uncommon for the removal of a dead sow to take two people more than an hour to accomplish without breaching biosecurity to deliver it outside of the building. When it is almost industry standard to be short of farm help, excess sow mortality creates a problem.
Sow mortality is variable across Canada depending on the animal’s health status, parity structure and many other factors. Recent mortality has been reported to be 9.6 percent on average but ranging from 5.4 percent to 15.5 percent. This is based on a PigCHAMP Benchmark summary from 2021, which can be found at www.pigchamp.com/benchmarking. For a 1,000 sow farm, the sow mortality could cost $134,000 per year.
Like all other livestock enterprises, there is an expected and accepted level of mortality, but if we can develop strategies to lower sow mortality on pig farms, we can realize savings approaching $14,000 per percentage point reduction.
A common contributor to sow loss on farms is the incidence of pelvic organ prolapse (POP). The swine sector has adopted this terminology, which may be different than other livestock sectors, because it is common to find sows that develop rectal, vaginal, uterine and various combinations of these prolapses when the muscle integrity or other factors result in the expulsion of those pelvic organs.
Unlike cattle and other species, replacement of the prolapse or surgical repair is not possible in a sow and these sows are euthanized at the farm.
A large collaborative study has been undertaken by researchers in the United States to evaluate risk factors that contribute to POP. Visit piglivability.org/pelvic-organ-prolapse for more information.
Identifying risk factors for prolapses on the farm will lead to further research into mitigation of POP and therefore reduction in sow mortality.
More than 400,000 sows were included across 104 herds with average sow herd total mortality determined to be 12.7 percent and sows dying or being euthanized due to POP ranging from 0.3 percent to 10.3 percent, for an average of 2.7 percent. That equates to one in every five dead sows as having a prolapse. The study evaluated more than 100 parameters that have been hypothesized to increase or decrease the incidence of POP.
Preliminary findings of the study require more research into these risk factors:
- Farms that treat drinking water (use chlorine or peroxide treatments) had lower POP incidence. In fact, POP was higher in farms using untreated well water compared to farms using untreated pond/surface collected water.
- Thin sows prolapse twice as much as adequately conditioned sows and four times more than over-conditioned sows. Furthermore, farms that bump-feed (provide additional feed each day for the last three weeks of pregnancy) had a lower incidence in thin sows.
- Dietary fibre is negatively correlated to POP. Farms feeding higher levels of fibre in gestation and lactation diets have lower incidence of POP.
- Perineal scoring was undertaken to assess sows that have varying degrees of “bulging” of the perineum (area around the rectum and vulva). Sows were assessed as they were lying down for how the perineum protrudes and how swollen the vulva appears. About one percent of sows with a score 1 (little to no bulge/swelling) went on to prolapse while 7.2 percent of sows with a score 3 (moderate to severe bulge/swelling) would eventually prolapse.
Other parameters assessed between these 104 farms that had weak associations (or the sample size of this study was not sufficient to detect a statistical relationship) include antibiotic use, feed mycotoxins, dietary fat levels, genetics, sow housing type (pens versus stalls) and the size of replacement gilts at first mating.
The parameters with a low or non-existent relationship to POP included farm size, hormone use for inducing birth, water delivery systems, insemination technique, farm hygiene, wet versus dry feed, particle size of the feed (how coarse or fine the grind is), tail length and herd level of farrowing assistance. Farms that have people attend most farrowing events were no different in POP incidence than those farms that leave sows to farrow on their own.
This study was limited by design to only describe trends in POP between farms rather than causation of prolapses. There is ongoing research into several areas identified in this initial study, including a focus on the perineal scoring and other physiologic differences in sows with varying degrees of perineal bulging.
Blaine Tully is a veterinarian and owner of Swine Health Professionals Ltd. in Steinbach, Man.
