The objectives of this study were to determine the effects of dietary supplementation with citrus flavonoid extracts (CFE) on milk performance, serum biochemistry parameters, fecal volatile fatty acids, fecal microbial community, and fecal metabolites in dairy cows. Eight multiparous lactating Holstein cows were used in a replicated 4 × 4 Latin square design (21-day period). Cows were fed a basal diet without addition (CON) or basal diet with added CFE at 50 (CFE50), 100 (CFE10), and 150 g/d (CFE150). Feeding CFE up to 150 g/d increased milk yield and milk lactose percentage. Supplementary CFE linearly decreased milk somatic cell count. Serum cytokines interleukin-1β (IL-1β), IL-2, IL-6, and tumor necrosis factor-α (TNF-α) concentrations decreased linearly as the levels of CFE increased. Cows in CFE150 had lower serum lipopolysaccharide and lipopolysaccharide binding protein compared with CON. These results indicate feeding CFE decreased systemic inflammation and endotoxin levels in dairy cows. Furthermore, feeding CFE linearly increased the concentrations of total volatile fatty acids, acetate, and butyrate in feces. The relative abundances of beneficial bacteria Bifidobacterium spp., Clostridium coccoides-Eubacterium rectale group, and Faecalibacterium prausnitzii in feces increased linearly with increasing CFE supplementation. The diversity and community structure of fecal microbiota were unaffected by CFE supplementation. However, supplementing CFE reduced the relative abundances of genera Ruminococcus_torques_group, Roseburia, and Lachnospira, but increased genera Bacteroides and Phascolarctobacterium. Metabolomics analysis showed that supplementary CFE resulted in a significant modification in the fecal metabolites profile. Compared with CON, fecal naringenin, hesperetin, hippuric acid, and sphingosine concentrations were greater in CFE150 cows, while fecal GlcCer(d18:1/20:0), Cer(d18:0/24:0), Cer(d18:0/22:0), sphinganine, and deoxycholic acid concentrations were less in CFE150 cows. Predicted pathway analysis suggested that "sphingolipid metabolism" was significantly enriched. Overall, these results indicate that citrus flavonoids could exert health-promoting effects by modulating hindgut microbiome and metabolism in lactating cows.

本研究的目的是确定在日粮中添加柑橘类黄酮提取物 (CFE) 对奶牛产奶性能、血清生化参数、粪便挥发性脂肪酸、粪便微生物群落和粪便代谢物的影响。在重复的 4 × 4 拉丁方设计（21 天周期）中使用八头经产泌乳荷斯坦奶牛。奶牛饲喂不添加 (CON) 的基础日粮或添加 50 (CFE50)、100 (CFE10) 和 150 g/d (CFE150) 的基础日粮。饲喂高达 150 g/d 的 CFE 可增加产奶量和牛奶乳糖百分比。补充 CFE 线性减少牛奶体细胞计数。血清细胞因子白细胞介素-1β (IL-1β)、IL-2、IL-6 和肿瘤坏死因子-α (TNF-α) 浓度随着 CFE 水平的升高呈线性下降。与 CON 相比，CFE150 奶牛的血清脂多糖和脂多糖结合蛋白较低。这些结果表明饲喂 CFE 可降低奶牛的全身炎症和内毒素水平。此外，喂食 CFE 会线性增加粪便中总挥发性脂肪酸、乙酸盐和丁酸盐的浓度。有益菌的相对丰度粪便中的双歧杆菌属、球形梭状芽孢杆菌-直肠真杆菌群和普拉梭菌随着 CFE 补充量的增加呈线性增加。粪便微生物群的多样性和群落结构不受 CFE 补充剂的影响。然而，补充 CFE 降低了Ruminococcus_torques_属、Roseburia和Lachnospira属的相对丰度，但增加了拟杆菌属和考拉杆菌属. 代谢组学分析表明，补充 CFE 会导致粪便代谢物谱发生显着变化。与CON相比，CFE150奶牛粪便柚皮素、橙皮素、马尿酸和鞘氨醇浓度更高，而粪便GlcCer(d18:1/20:0)、Cer(d18:0/24:0)、Cer(d18:0) /22:0)、二氢鞘氨醇和脱氧胆酸浓度在 CFE150 奶牛中较低。预测通路分析表明“鞘脂代谢”显着丰富。总的来说，这些结果表明柑橘类黄酮可以通过调节泌乳牛的后肠微生物组和新陈代谢来发挥促进健康的作用。