mRNA expression of components of the IGF system and of GH and insulin receptors in ovaries of broiler breeder hens fed ad libitum or restricted from 4 to 16 weeks of age.

An evaluation of the insulin-like growth factors (IGF) system in the ovaries of heavy breeder hens during the growing phase was performed to measure the effect of feed restriction. The transcripts of IGF-I, IGF-II, IGF receptor (IGF-R), two IGF binding proteins (IGFBP-2 and IGFBP-5), GH receptor (GH-R) and insulin receptor (I-R) were measured by RT-PCR at 4, 8, 12 and 16 weeks of age in the ovaries of ad libitum fed and feed restricted hens. The transcripts of all genes screened were detected in all feed regime groups and at all ages sampled. However, no significant overall effects of feed restriction on these transcripts were found despite the marked difference in body growth (200% at 16 weeks of age). Similarly there were no significant age effects except for the expression of GH-R-that showed a decrease after 8 weeks of age (P<0.01). Although feed restriction seems to have a relatively limited effect on the expression of these components of the ovarian IGF system in juveniles, a more detailed determination is necessary to determine possible changes nearer to sexual maturity (16 weeks of age onwards). It is concluded that components of the IGF system, GH or insulin may not be involved in the mechanisms that, through restricted feeding, alter ovarian development and function during growth to enable better reproductive performance during lay.