Fermented Chinese Herbs Improved Egg Production, Egg Shell Quality, and Egg Yolk Cholesterol of Laying Hens by Regulating Estrogen, Lipid Metabolism, and Calcium Metabolism

The present study investigated the effects of fermented Chinese herbal (FCH) compounds on the egg production, egg shell quality, and egg yolk cholesterol of laying hens. A total of 1260 Hy-Line pink laying hens, 34 weeks old, were randomly divided into three groups, with six replicates per group and 70 hens per replicate, as follows: the control group (CON group) was fed a diet without FCH compounds, and the 2% FCH group and the 3% FCH group were fed a diet supplemented with 2% FCH and 3% FCH, respectively. The results show that the FCH compound significantly increased the laying rate compared to the CON group (p < 0.05). Analyses of the serum biochemical indices showed that supplementation with FCH compound significantly decreased the levels of total cholesterol (TC), total triglyceride (TG), high-density lipoprotein cholesterol (HLDL-c), low-density lipoprotein cholesterol (LDL-c), very-low-density lipoprotein cholesterol (VLVL-c), aspartate transaminase (AST), and alanine aminotransferase (ALT) (p < 0.05) and increased the serum total bile acids, follicle-stimulating hormone (FSH), luteinizing hormone (LH), and 17-β-Estradiol (E2) levels (p < 0.05). The FCH group significantly increased the activity of superoxide dismutase (SOD) and total antioxidant capacity and decreased malondialdehyde (MDA) levels in the liver and uterus compared to the CON (p < 0.05). FCH supplementation was also associated with improved egg quality, seen through factors including enhanced yolk color, albumen height, Haugh unit score, eggshell strength, and thickness and reduced egg breaking rate and TC and TG contents in egg yolk. The gene expression analyses showed that FCH supplementation significantly increased the calcium metabolism-related gene expression (CaBP-D28k, NCX, VDR, CYP27B1, OPN, PMCA, CA2) in duodenum, kidney, and uterus tissues compared to the CON group (p < 0.05). FCH significantly repressed FAS and HMGCR mRNA expression and enhanced CYP7A1 mRNA expression in the liver (p < 0.05). These results indicate that diet supplementation with FCH compounds may improve egg quality by regulating reproductive hormones, lipid metabolism, and calcium metabolism.