When, in a sow's life, does litter size start to decline?

Litter size in sows typically begins to decline after a certain number of litters due to factors such as age, reproductive efficiency, and health status. Research has shown that the most significant decline in litter size usually occurs after the sixth litter. This is primarily because, as sows age, their reproductive performance tends to diminish. This decline can be attributed to factors like increasing age-related physiological changes and potential accumulated effects of breeding and farrowing stress over time.

The earlier litters often benefit from more favorable conditions and a more youthful reproductive system, which is why litter size remains relatively stable before that sixth litter. Beyond the sixth litter, producers may notice a more consistent decline which often leads to decisions regarding culling or replacement of sows in their breeding program to maintain overall productivity.