Introduction Historically, pig breeding programs have focused on a limited number of traits. Often growth rate, back fat and a measure of litter size at birth were the only traits considered. Genetic relationships with other unrecorded traits were ignored in this simple approach, although selection for these traits leads to correlated responses in feed efficiency, lean meat growth, carcase characteristics, meat quality, survival of piglets, disease resistance as well as characteristics of the sow such as mature weight, body composition and feed intake capacity. This long list of traits may seem daunting. However, ignoring (unfavourable) genetic associations between traits in pig breeding programs will lead to sub-optimal performance and ultimately impair health and welfare of pigs and sows (e.g. Rauw et al., 1998; Prunier et al., 2010).
Ten years ago, Jaco Eissen (Eissen, 2000) proposed selection for a higher feed intake during lactation as a strategy to overcome longevity and reproductive problems in sows, which were thought to be largely due to a widening gap between nutrients available from decreasing fat reserves at farrowing and nutrients required to meet increasing demands of litters. However, focus on a single trait is inadequate, given the complex associations between the physiological states of sows during transition from gestation to lactation and finally to mating following the weaning process. In addition, various physiological parameters of the sow may interact with the changing requirements of the litter during gestation and lactation.
Genetic and phenotypic relationships between sow weight and body composition, lactation feed intake, reproductive traits of sows and lean meat growth of growing pigs have been outlined in a number of papers presented at this workshop, as well as the previous workshop in 2008. In this paper we look at some common paradigms in regard to sow and piglet performance and try to place them in context with alternative management or selection choices that could be made.