Feed restriction inhibits early follicular development in young broiler-breeder hens

Ad libitum feeding causes excessive follicular development and is associated with extensive metabolic changes in broiler-breeder hens. Restricting feed intake reduces excessive follicular development, but the mechanisms mediating this response are unknown. In the present study, the effects of feeding on follicular development in immature broiler-breeder hens were examined. There was an increase in the proportion of follicles 100-300, 300-500 and >500 μm in diameter and a decrease in follicles <100 μm in full-fed (FF) compared to restricted-fed (RF) hens. Increased follicular development in FF hens was associated with a greater expression of steroidogenic transcripts (STAR, CYP11A1, HSD3B, and CYP19) within the ovarian cortex of FF hens. These transcripts represent markers of more advanced follicular development. However, increased follicular development in FF hens was not associated with changes in the expression of other factors previously implicated in follicular development, including those encoding TGF-beta ligands (AMH, BMP6, BMP15, or GDF9) or their signaling proteins (SMAD2/3 or SMAD1/5/9). Changes in histone modifications associated with proliferation, including trimethylated histone H3K4, trimethylated histone H3K27, and acetylated histone H3K9, were also not different between treatment groups. However, feed restriction caused serine phosphorylation to localize strongly to the ovarian stroma of FF hens compared to RF hens. In contrast, phosphorylation of tyrosine residues localized more prominently to the surface of granulosa cells from RF hens. Thus, restricted feeding may enhance the efficiency of reproduction by suppressing early follicular development which is associated with changes in granulosa cell protein phosphorylation status.