Domestication and intense genetic selection in chickens have resulted in highly efficient meat (broiler) and egg-producing (layer) breeds. The work reported in this dissertation explores differences between hens with different egg-laying rates in two breeds of chickens and factors involved in follicle development. Intense selection in broiler hens has caused suboptimal reproduction, which can be alleviated by restricting feed intake. In the first study, using RNA-sequencing, we investigated transcriptional differences in granulosa cells of 6-8 mm follicles from broiler breeder hens fed at different levels. RNA-sequencing analysis revealed genes involved in steroidogenesis and FSH regulation were upregulated in broiler breeder hens fed ad libitum. IGF1 and FSH were identified as upstream regulators of these genes that could influence genes involved in follicle development. A second study investigated the role of IGF1 treatment in vitro in the presence and absence of FSH in granulosa cells of prehierarchal follicles. Several genes upregulated in broiler breeder hens fed ad libitum were increased by IGF1, and FSH enhanced the expression of some genes. Laying hens are extremely reproductively efficient during their first year; however, the average egg-laying rate of a flock decreases after the first year, leading producers to cull hens. Within this average are hens that continue to lay at a high rate and hens with a marked decline of egg-laying rate. Hens exhibiting persistent laying rates (PL, 100% egg-laying rate) and nonpersistent laying rates (NPL, ~80% egg-laying rate) were selected for retrospective and ovarian analysis. PL hens had higher body weights and egg-laying rates earlier in life. At the ovarian level, PL hens had more follicles, lower rates of atresia in <100 µm follicles, and higher AMH and BMP15 mRNA expression. The final study investigated the regulation of AMH by FSH and the functional role of AMH using RNA-interference in granulosa cells of 3-5 mm and 6-8 mm follicles. FSH decreased AMH mRNA expression in 3-5 mm but not 6-8 mm follicles. AMH did not affect mRNA expression of follicle development markers examined in the presence or absence of FSH. The work in this thesis provides new insights into the physiology underlying follicle development and egg-laying rates.