Estimates of Genetic Correlations between IGF-1 recorded at 4 weeks of age and individual piglet weights at birth and 14 days, along with lifetime growth rate and backfat

Insulin-like growth factor-1 (IGF-1) was recorded for 9990 pigs at four weeks of age. These data were used to estimate genetic correlations between juvenile IGF-1 and performance traits recorded on the piglet or at later ages. Estimates of heritability and litter effects for IGF-1 were 0.24±0.03 and 0.13±0.01. The genetic correlation between juvenile IGF-1 and piglet weight at birth (IPWB) was -0.33±0.19. In contrast, juvenile IGF-1 had a low positive genetic correlation with piglet growth rate from birth to 14 days (ADG14). A similar pattern of genetic correlations was observed between backfat (BF) and piglet traits. Backfat had a negative genetic correlation with IPWB (r_g: -0.43±0.17), but a positive genetic correlation with ADG14 (r_g: 0.15±0.19). Further, juvenile IGF-1 had a strong positive genetic correlation with BF (r_g: 0.46±0.08). These genetic correlations support a downward selection strategy for juvenile IGF-1. It is speculated that these results, in combination with those from other studies, provide clues as to why juvenile IGF-1, in contrast to IGF-1 measured in finishing pigs, is an appropriate selection criterion for improving the efficiency of lean meat production.