The improving effect of soybean isoflavones on ovarian function in older laying hens

Emerging evidence suggests an associa-tion between estrogen levels and reduced egg-laying per-formance as the layer became old. Since soy isoflavones (SF) have estrogen-mimic effects, whether it can enhance production performance and ovarian function of older layers is still not known. A total of 160 Lohmann pink layers (66-wk-old) were used in a 2 & POUND; 2 factorial design, which included 2 egg-laying levels [low (76.89 & PLUSMN; 1.65%; LOW) and normal (84.96 & PLUSMN; 1.01%; NOR)] and 2 different dietary groups [0 mg/kg SF, 20 mg/kg SF] were used. The results showed the NOR group had higher egg-laying rate, egg mass, and feed efficiency dur-ing the all phases (P(laying) < 0.05). The unqualified egg rate was lower in NOR group (9-12 wk, 1-12 wk) (P(laying) < 0.05). Dietary supplementation with SF increased the egg-laying rate and feed efficiency (5-8 wk, 9-12 wk, 1-12 wk), increased egg mass (9-12 wk, 1-12 wk) (P(SF) < 0.05). The NOR layers presented higher eggshell quality (redness, yellowness, brightness, eggshell ratio) at 12 wk (P(laying) < 0.05). Eggshell quality was found to be improved by SF (egg-shell strength and eggshell thickness), egg albumen quality (higher albumen height and Haugh unit) at 12 wk (P(SF) < 0.05). Supplementing with SF led to an increase in eggshell strength in LOW group (P(laying*SF) < 0.05). The higher serum lever of glucose (GLU) and lower serum lever of follicle stimulating hormone (FSH) were in NOR group (P(laying) < 0.05). Supplementing SF in diets increased serum of estradiol (E2) and insulin -like growth factors-1 (IGF-1), decreased serum of FSH (P(SF) < 0.05). The NOR layers presented lower estrogen receptor a (ERa), estrogen receptor b (ERb), B lym-phoma 2 associated X protein (Bax), cytochrome c (Cytc), interleukin 6 (IL-6), caspase3, caspase9, IKKa, P50, and P65 expression in the ovary (P(laying) < 0.05). Dietary SF supplementation decreased the anti-Mueurollerian hormone receptor (AMHR), Bax, caspase3, caspase9, Cytc, IL-6, IKKa, P50, P65 expression in the ovary (P(SF) < 0.05). These findings indicated that layers with NOR group had higher production perfor-mance, egg quality, and ovarian function, while dietary supplementation with SF improved production perfor-mance and ovarian function by reducing inflammation and apoptosis-related genes expression in ovary.