Genetic correlations of growth, backfat thickness and exterior with stayability in large white and landrace sows

Backfat thickness, daily gain, and five exterior traits were measured in 36 814 Large White and Landrace gilts from nucleus and multiplier herds. Functional stayability, defined as survived (1) or not (0), from first to second (STAY12) and from first to third litter (STAY123) was available for 13 760 of these animals in a commercial multiplier environment. Heritabilities and genetic correlations of longevity and growth performance and exterior traits were estimated by linear models. Heritability estimates for STAY12 and STAY123 in Large White were 0.08 and 0.10, and in Landrace 0.07 and 0.11, respectively. The corresponding genetic standard deviations for STAY123 were 0.118 and 0.126 in Large White and Landrace, respectively. Antagonistic genetic correlations were found between stayability traits and backfat thickness and daily gain. Estimates ranged from 2 0.06 to 2 0.32 for daily gain and from 0.11 to 0.27 for backfat thickness in both lines. Genetic correlations with leg score were about zero in Large White and positive (from 0.19 to 0.36) in Landrace, whereas genetic relationships with other exterior traits were near zero. We conclude that the selection for longevity is possible because of high genetic standard deviations of the stayability traits and that an antagonism exists between growth performance and longevity, whereas a better leg status decreases involuntary culling.  2000 Elsevier Science B.V. All rights reserved.