Changes in Plasma Insulin-like Growth Factor (IGF)-1, IGF Binding Protein (IGFBP)-2 and IGFBP-3 during Fasting in Holstein Adult Steers and Calves

This study was conducted to investigate the effect of fasting on plasma insulin-like growth factor (IGF)-1, IGF binding protein (IGFBP)-2 and IGFBP-3 in two different growth stages of Holstein steers. Eight 4 month-old Holstein steer calves were treated with normal feeding and fasting for 3 days and four 18 month-old Holstein adult steers were treated 6 days. Plasma IGFBP-2 and IGFBP-3 were determined by western immunoblotting using the rabbit anti-bovine IGFBP-2 and-3 following SDS-PAGE electrophoresis. The immnunoblotting analysis demonstrated that the plasma IGFBP-3 band appeared at 38-43 kDa and plasma IGFBP-2 was localized at 34 kDa in plasma of adult and calves. Plasma IGF-1 and IGFBP-3 levels were higher in adult steers than calves (P