Expression of anti-Mullerian hormone in hens selected for different ovulation rates

In hens, the granulosa layer is the primary source of anti-Mullerian hormone (AMH), as it is in mammals. Small follicles express the greatest amount of Amh mRNA with less in the larger follicles. Laying hens have a distinct ovarian hierarchy of follicles while broiler breeder hens often have excessive follicle growth with a disrupted hierarchy. The objective of Experiment 1 was to examine Amh expression in two strains of hens differing in ovulatory efficiency. Amh expression was greater (P<0.01) in broiler breeder hens (n=6) as compared with laying hens (n=6). Experiment 2 was designed to examine whether alterations in follicular development due to diet, within the broiler breeder hens, were correlated with changes in the expression of Amh. Restricted feeding (RF) in broiler breeder hens promotes optimal follicular development. Egg production in broiler breeder hens on full feed (FF; n=8) was 78% that of hens on RF (n=9). The number of large follicles (P<0.05), total ovarian weight (P<0.01), and Amh mRNA expression were greater in FF hens as compared with RF hens (P<0.01). There was no difference in FSH receptor expression between the two groups. A direct nutritional effect was not supported because culture of granulosa cells with varying concentrations of glucose and insulin showed no effect on granulosa Amh expression. Finally, testis-conditioned medium resulted in a dose-related increase in granulosa cell proliferation, which could be inhibited by preincubation with AMH antibody. AMH may enhance granulosa cell proliferation through an autocrine or paracrine mechanism although excessive AMH may inhibit optimal follicle selection.