Genetic variation in growth patterns is associated with sow lifetime performance

Longitudinal data for weight and fat from up to 19 recording events were used in random regression (RR) analyses to generate estimates of additive genetic and permanent environmental effects for sow development attributes up to parity 5. Sows (N=3324) were then ranked in quartiles using solutions from the RR for additive genetic effects which separately describe intercept and slope, generating 16 combinations (intercept x slope) for development trajectories within trait. Lifetime productivity of sows was compared between these groups. Genetic variation in development trajectories was evident, but similar phenotypes can arise from different trajectories. Differences in lifetime productivity, measured as the total number of piglets born (LTB) or litters produced (LPL) prior to culling, was significantly associated with genetic differences in development patterns. While sows survived and reproduced over a wide range of body weights and adiposity levels, generally heavier and fatter sows were more likely to enter the breeding herd successfully. However, sows with low rank for intercept combined with high rank for slope, putatively representing a "later" development pattern that should increase competition for limited resources in the breeding sow, had significantly (P<0.0001) reduced LPL and LTB in particular. This outcome suggests that associations between traits like body weight and fatness with sow lifetime performance are not independent of the timing in body development relative to the physiological demands of reproduction.