Profiling growth performance, insulin-like growth factors, and IGF-binding proteins in rainbow trout lacking IGFBP-2b

Knocking out IGFBP-2b in rainbow trout improved food intake, growth performance, and feed conversion ratio and reduced serum IGF-1 by 0.5- to 0.8-fold, without changes in the concentration of free serum IGF-1. Based on these findings, we propose that, in addition to IGFBP-2b, the 32-kDa IGFBP (putative IGFBP-2a) also serves as a major carrier of circulating IGF-1 in salmonids.