Rectal microbiomes and serum metabolomics reveal the improved effect of Artemisia ordosica crude polysaccharides on the lactation performance, antioxidant and immune responses of lactating donkeys

This study is aimed at investigating the effects of dietary supplementation with Artemisia ordosica crude polysaccharides (AOCP) on lactation performance, antioxidant status, and immune status of lactating donkeys and analyzing rectal microbiomes and serum metabolomes. Fourteen lactating Dezhou donkeys with similar age (6.16 ± 0.67 years of BW ± SD), weight (250.06 ± 25.18 kg), days in milk (39.11 ± 7.42 d), and averaged parity of 3 were randomly allocated into 2 treatments: a control group (CON, basal diet) and an AOCP group (AOCP, basal diet with 1.0 g/kg DM AOCP). Ten weeks were allotted for the experiment, 2 weeks for adaptation, and 8 weeks for collecting data and samples. The results showed that supplementation of donkey diets with AOCP increased lactation performance, including dry matter intake, milking yield, estimated milk yield, solids-corrected milk, energy-corrected milk, milk fat yield, milk protein yield, milk lactose yield, milk total solids yield, and milk solid not fat yield. The digestibility of dry matter, crude protein, acid detergent fiber, and neutral detergent fiber was increased in the AOCP group compared with the CON group. The AOCP group increased the concentrations of immunoglobulin A, immunoglobulin G, and immunoglobulin M, the activities of the superoxide dismutase, catalase and total antioxidant capacity in the serum. AOCP decreased the concentrations of tumor necrosis factor-α, nitric oxide, reactive oxygen species, and malondialdehyde in the serum. Compared with the CON group, AOCP increased propionate, butyrate, isovalerate, and total VFA concentrations in rectal feces (P < 0.05). The addition of AOCP to increased diversity (Shannon index) and altered structure of the rectal microflora. As a result of AOCP supplementation, there has been a significant improvement in the colonization of beneficial bacteria, including Lactobacillus, Unclassified_f_Prevotellacea, Ruminococcus, and Fibrobacter genera. In contrast, a decrease in the colonization of the Clostridium_sensu_stricto_1 bacterial genus and other pathogenic bacteria was observed. Meanwhile, metabolomics analysis found that AOCP supplementation upregulated metabolites L-tyrosine content while downregulating 9(S)-HODE, choline, sucrose, LysoPC (18:0), LysoPC (18:1(9Z), and LysoPC (20:2(11Z,14Z)) concentrations. These altered metabolites were involved in the PPAR signaling pathway, prolactin signaling pathway, glycerophospholipid metabolism, carbohydrate digestion and absorption, and tyrosine metabolism pathways, which were mainly related to antioxidant capacity, immune responses, and protein metabolism in the lactating donkeys. As a consequence of feeding AOCP diets, beneficial bacteria were abundant, and antioxidant and protein metabolism-related pathways were enriched, which may enhance lactation performance in donkeys. Therefore, supplementing AOCP diets is a desirable dietary strategy to improve donkey health and lactation performance.