Abstract
The objective of this experiment was to investigate the effects of tartary buckwheat flavonoids (TBF) and 25-hydroxyvitamin D(3) (25-OHD) on fatty liver syndrome (FLS) in laying hens. A total of 450 35-wk-old Lohmann laying hens were selected and randomly divided into five groups, with six replicates per treatment and 15 laying hens in each replicate. The control group was fed a corn-soybean meal basal diet. The FLS group was fed a high- energy-low-protein (HELP) diet, and the other three experimental groups were fed HELP diets supplemented with 60 mg/kg TBF, 69 μg/kg 25-OHD, and 60 mg/kg TBF plus 69 μg/kg 25-OHD, respectively. The experiment lasted 8 weeks. The results demonstrated that feeding laying hens with a HELP diet led to a significant accumulation of fat in their livers, liver enlargement and yellowing, as well as a decline in liver antioxidant capacity and an aggravation of inflammation. TBF alone, 25-OHD alone, and their combination had no effect on the laying performance of laying hens fed with a HELP diet. However, 25-OHD significantly enhanced the albumin content, eggshell strength, and eggshell thickness of eggs (p < 0.05). Compared with the HELP group, TBF, 25-OHD, or their combination reduced serum LDL-C and TG (p < 0.05). The combined treatment further lowered serum NEFA and MDA, enhanced liver SOD activity (p < 0.05), and unlike TBF alone (which reduced hepatic TG) or 25-OHD alone (which decreased liver index), reduced both liver index and hepatic TG (p < 0.05). Liver gene expression analysis showed that combined TBF and 25-OHD significantly inhibited the expression of fat synthesis-related genes (ACC, FAS, GPAT1, ChREBP1, LXRα, SREBP-1C, SREBP-2, FABP) as well as inflammation-related genes (IL-6, TNF-α, NF-κB, TLR4) (p < 0.05). At the phylum level of the cecal microbiota, TBF increased the abundance of Bacteroidota (p < 0.05), and combined TBF and 25-OHD tended to increase the abundance of Firmicutes_D. At the genus level, TBF increased the abundance of Phocaeicola_A (p < 0.05). Furthermore, TBF, 25-OHD, or their combination reduced the abundance of Faecalibacterium (p < 0.05). These findings suggest that combined TBF and 25-OHD mitigates FLS in laying hens potentially through remodeling gut microbiota and maintaining lipid metabolic homeostasis.