Dietary supplementation of Citrus bioflavonoids improves lactation performance in buffaloes during hot weather by regulating antioxidant capacity, immune function, and rumen microbes

<i>Citrus</i> bioflavonoids (CB) are well recognized for their antioxidant, anti-inflammatory, and digestion-promoting properties. This study aimed to evaluate the effects of dietary CB supplementation on apparent nutrient digestibility, lactation performance, blood biochemical/immunological parameters, and the ruminal microbial community of dairy buffaloes during hot weather. A 35-day trial was conducted using 20 Mediterranean dairy buffaloes, which were randomly assigned to two groups: a control group (CON) fed a basal diet, and a CB-supplemented group (CB) fed the basal diet plus 20 g/d of CB. The results showed that compared with the CON group, CB supplementation significantly reduced (<i>p</i> < 0.05) the respiratory rate, and increased (<i>p</i> <b><</b> 0.05) the apparent digestibility of acid detergent fiber in buffaloes. Regarding lactation performance, CB supplementation significantly elevated (<i>p</i> <b><</b> 0.05<b>)</b> milk yield, 4% fat corrected milk, and the percentage of milk protein, lactose, and solids-not-fat; it also increased the concentrations of polyunsaturated fatty acids and conjugated linoleic acids in milk while decreasing (<i>p</i> < 0.05) the concentration of saturated fatty acids. For blood parameters, the CB group exhibited significantly higher (<i>p</i> < 0.05) blood catalase activity, immunoglobulin M concentration, and heat shock protein 70 concentration, as well as significantly lower (<i>p</i> < 0.05) concentrations of the pro-inflammatory cytokines tumor necrosis factor-<i>α</i>, interleukin (IL)-1β, and IL-6. In terms of ruminal function, CB supplementation significantly increased (<i>p</i> < 0.05) ruminal microbial crude protein concentration. There was a tendency toward higher (0.05 < <i>p</i> < 0.10) microbial <i>α</i>-diversity indices (Chao 1, Ace, and Shannon) in the CB group, accompanied by the enrichment of several bacterial genera within the family <i>Lachnospiraceae</i> and other saccharolyti<i>c</i> taxa, and the suppression of the genus <i>Segatella</i>. In conclusion, dietary supplementation with 20 g/d CB enhances the lactation performance of heat-stressed dairy buffaloes by improving the ruminal microenvironment and host health status.