Animal Welfare

Lame Sows Culled Most Often

Highly productive, lame sows are more likely to be culled and removed from the herd shortly after farrowing than other sows in the herd, according to research from the University of Minnesota.

After reproductive reasons, lameness is the second-highest reason for culling sows.

Research indicates that this problem plagues first-litter sows due to a higher risk of locomotor problems.

By reducing the number of sows culled for lameness, the proportion of sows of higher parity would rise in the herd, enhancing sow longevity and bringing with it the associated advantages of litter size and farrowing rate, the Minnesota researchers surmise.

The Minnesota study characterized sow removals from breeding herds based on cumulative results for culling, death and euthanasia for 120 days postfarrowing. The study analyzed the association between culling due to lameness and sow productivity traits among the sows culled. Data was obtained from PigChamp records for removal of 51,795 sows from 11 Canadian farms during January 1991 to December 2002.

The data supported the position that the proportion of deaths (euthanasia and natural deaths) among removed lame sows during lactation was higher than the culling proportion, the researchers noted.

For the sows removed, 49% of deaths and 45% of euthanasia occurred by 20 days postfarrowing, whereas by this time only 14% of normal culling was done.

In breaking down sow culling rates postfarrowing for Parity 1 lame sows, 20% of the deaths occurred by 10 days postfarrowing, and the proportion of deaths increased to 38% in the next 10 days.

By 20 days after farrowing, 40% euthanasia for lameness had occurred for Parity 1 lame sows, compared to a cumulative culling rate for lameness of only 24% for the herds reviewed.

For lame sows of Parity 2 and greater, 45% of the deaths and 41% of the euthanasia occurred within 20 days of farrowing. That compared to a cumulative culling rate due to lameness of only 25%.

Sows culled due to lameness were more likely to have been culled in non-summer months, when odds were greater that sow production was higher.

Likewise, chances of culling due to lameness declined for Parity 1 sows when average number of non-productive sow days increased.

In lame sows greater than Parity 2, the odds of being culled were higher for Parity 2-5 sows than for sows greater than Parity 5.

In short, highly productive sows were more likely to have been recorded as lame as a reason for culling. Highly productive sows are more susceptible to conditions such as osteomalacia (related to calcium deficiency), because there are physical limitations on the amount of feed a sow can eat to replenish minerals secreted during lactation.

Pregnancy or lactation may affect the decision to cull, even if the sow is lame.

The Minnesota research team concluded that lameness should be either prevented or treated.

Once a sow is identified as lame, and when treatment is not an option, it should be culled/euthanized without delay to avoid further pain for the animal.

Researchers: Sukumarannair S. Anil, DVM; John Deen, DVM; Leena Anil, DVM, University of Minnesota. Contact Deen by phone (612) 625-7784; fax (612) 625-1201; or e-mail deenx003@umn.edu.