Developmental changes in amniotic and allantoic fluid insulin-like growth factor (IGF)-I and -II concentrations of avian embryos

In the literature, IGFs in the developing embryo are usually determined by blood serum concentrations. For this study, IGF-I/-II was quantified in the amniotic and allantoic fluids of fertile commercial broiler chicken (Gallus domesticus) (n = 222), Pekin duck (Anas platyrhyncha) (n = 250), and turkey (Meleagridis gallopavo) eggs (n =  200) during incubation. Amniotic and allantoic fluids were collected from embryos starting at 6 days of incubation for chickens and 8 days of incubation for ducks and turkeys. IGF concentrations within the fluids were determined by radioimmunoassay. Chicken amniotic IGF-I concentration at stage 29 of development was significantly higher (P ≤ 0.05) than the duck or turkey. At stage 36 of development the concentration of IGF-II in the amniotic fluid was 2.8 times greater in the chicken versus the duck (P ≤ 0.05) and 2 times greater than in the turkey (P ≤ 0.05). Within species, chicken IGF-I concentration in the amniotic fluid had a cubic trend (P ≤ 0.001), duck IGF-I increased linearly (P ≤ 0.001), and turkey concentrations declined quadratically (P ≤ 0.001) throughout development. In all species, the IGF-II concentration was higher than the IGF-I concentration in the amniotic and allantoic fluids.