The Effect of Breeding Herd Parity Structure on Genetic Improvement of the Sow Herd

This study focuses on the value of the genetic lag associated with maintaining sows for additional parities in a commercial swine herd. Three traits were included in this study: number born alive (NBA), 21 day litter weight (W21), and days to market (D250). The economic values assigned to these traits were $22.00/pig, $0.70/lb., and $0.17/day, respectively. The genetic improvement per generation made for each trait was assumed to be 0.3 pigs, 3.0 lbs., and 3.0 days, respectively. It was estimated that the value of the genetic lag associated with retaining a sow to P3, P5, and P7 was $24.80, $46.89, and $73.97 in a herd whose seedstock supplier has a generation interval of 1.5 years. This minimal loss does not justify the costs of developing a gilt and decreased P1 production. Therefore, sows should remain in the breeding herd until culling for non-voluntary reasons or inferior production becomes necessary