Juvenile IGF-I Response in INRA RFI Selection Lines Partly Reflects Changes in Post-Weaning Attributes

Performance data were recorded at INRA in two lines divergently selected for residual feed intake (RFI) for eight generations (G0 to G7). A subsample of piglets were bled shortly after weaning to establish concentrations of juvenile IGF-I. The line effect was clearly detected for juvenile IGF-I, confirming previous studies which found that juvenile IGF-I is an indirect early predictor of efficiency. The line difference in juvenile IGF-I was partly explained by differences between the RFI lines in their growth immediately after weaning, but remained significant after post-weaning growth was accounted for. Selection for efficiency has implications for postweaning management to limit feed deprivation and growth delays during the post-weaning period.