The objective of this experiment was to investigate the effects of tartary buckwheat flavonoids (TBF) and 25-hydroxyvitamin D₃ (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.

The present work was designed to investigate the impacts of tartary buckwheat flavonoids (TBF) on the growth performance and physiological metabolism of Liangshan Yanying chickens. A total of 144 healthy 4-week-old Liangshan Yanying chickens of uniform body weight were randomly divided into four groups. Each group consisted of six replicates with six chickens per replicate. The control group was fed a basal diet, whereas the treatment groups received the same basal formulation supplemented with TBF at concentrations of 20, 40, and 60 mg/kg, respectively. The entire feeding trial lasted for 10 consecutive weeks. Growth performance, serum parameters, bone quality, slaughter traits, and hepatic lipid metabolism were determined and statistically analyzed. Results showed that dietary TBF supplementation had no significant impact on the overall growth performance (p > 0.05); however, final body weight and average daily weight gain displayed a positive linear trend in response to increasing TBF levels (0.05 < p < 0.1). For serum parameters, TBF supplementation significantly increased total antioxidant capacity (p < 0.05) and decreased malondialdehyde content (p < 0.05) in a linear manner. Specifically, compared with the control group, the 60 mg/kg TBF group increased T-AOC by approximately 64.6% and reduced MDA by approximately 67.9%, demonstrating a robust antioxidant effect. A linear increase in high-density lipoprotein cholesterol levels approaching significance (p = 0.055) was also observed. A significant quadratic regulatory effect of TBF was observed on serum glucose concentrations (p < 0.05), whereby the 60 mg/kg TBF dose reduced serum glucose by 15.6% relative to the control (p < 0.05), reflecting a robust hypoglycemic effect. Regarding bone quality, supplementation with 20 and 60 mg/kg TBF significantly elevated tibial phosphorus content relative to the 0 mg/kg TBF group (p < 0.05). Regression analysis showed that increasing dietary TBF levels linearly elevated tibial calcium content (p < 0.05) and resulted in linear increasing trends in tibial ash content, tibial phosphorus content, femur ash content, and femur calcium content (0.05 < p < 0.1). Concerning slaughter performance, dietary TBF inclusion resulted in a significant linear rise in breast muscle percentage (p < 0.05). At the molecular level, TBF upregulated the mRNA expression of hepatic AMPKα1 and CPT1, while concurrently downregulating the expression of FAS and ACC (p < 0.05). Collectively, dietary TBF supplementation in Liangshan Yanying chickens effectively improved antioxidant capacity, promoted tibial calcium and phosphorus deposition, regulated hepatic fatty acid oxidation and synthesis via AMPK-related genes, and enhanced lean meat deposition, with no adverse effects on growth performance under the experimental conditions.