Excellent Performance with Larger Litters in Free-Farrowing Pens

Since 2007, only free-farrowing pens may be used in Switzerland. Since then, litter size has increased significantly. Despite this, piglet mortality during the lactation period has remained stable over the years.

Since 2007, farrowing pens in Switzerland must be designed so that the sow can turn freely – unlike in other countries such as Germany or Denmark, where sows may still be kept in farrowing crates. Since then, litter size has increased significantly. It is therefore of interest for Swiss pig producers to know whether piglet losses in free-farrowing pens have increased with bigger litters, with negative economic consequences.
Researchers at the Centre for Proper Housing of Ruminants and Pigs in Tänikon investigated the trend in piglet losses in recent years, evaluating 9714 litters from 96 farms from 2003 as well as 331,820 litters from 255 farms from 2008 to 2017.

Piglet mortality stable despite larger litters

During this period – as in other countries – targeted breeding significantly increased litter size in Switzerland. Thus, in 2003 11.1 piglets per litter were born live, whilst the figure rose to 12.8 for 2017. As expected, with increasing litter size, more piglets died before weaning. This is because more low-weight piglets with a lower survival rate are born in larger litters.
Despite this, a comparison of piglet losses from 2003 and 2017 shows that there were no significant differences for any causes of loss (total losses, crushing losses and other losses). In 2003, an average 11.7% of piglets per litter died before weaning, whilst the figure was 11.1% for 2017.
From the 13th live-born piglet onwards, however, the number of piglets weaned per litter hardly increased further (Fig. 1), and the 14th and 15th live-born piglet had a likelihood of about 40% and 70%, respectively, of dying before weaning.

No point in further increasing litter size

This study shows that breeding for even larger litters is not recommendable. With additional live-born piglets, the increase in the number of weaned piglets per litter flattens out markedly. This is why since 2003, the Swiss pig-breeding organisation has weighted litter size less heavily, whilst the rearing performance of the sow as well as the percentage of underweight piglets have been taken into account as new breeding traits.