Donkey milk is a traditional medicinal food with various biological activities. However, its production is very low, and lactating donkeys often experience oxidative stress, leading to a further decline in milk yield. In this study, we supplemented the diets of lactating donkeys with yeast selenium (SY) to investigate its effects on lactation performance, antioxidant status, and immune responses, and we expected to determine the optimum additive level of SY in the diet. For this study, 28 healthy lactating Dezhou donkeys with days in milk (DIM, 39.93 ± 7.02 d), estimated milk yield (EMY, 3.60 ± 0.84 kg/d), and parity (2.82 ± 0.48) were selected and randomly divided into 4 groups of 7 donkeys in each: Group SY-0 (control), Group SY-0.15, Group SY-0.3, and Group SY-0.5, with selenium supplementation of 0, 0.15, 0.3, and 0.5 mg of Se/kg DM (in form of SY) to the basal diet, respectively. The results showed a dose-dependent increase in milk yield, milk component yield, milk protein production efficiency, milk production efficiency, the activities of glutathione peroxidases (GSH-Px), catalase (CAT), and total antioxidant capacity (T-AOC), as well as the content of serum interleukin-10 (IL-10), white blood cells (WBC), lymphocytes (LYM), red blood cells (RBC), hematocrit, plasma selenium, and milk selenium. Conversely, it presented a dose-dependent decrease in the activity of nitric oxide synthase (iNOS) and the contents of malondialdehyde (MDA), reactive oxygen species (ROS), nitric oxide (NO), interleukin-1β (IL-1β), interleukin-6 (IL-6), and interferon-γ (IFN-γ). In conclusion, the results confirmed that dietary supplementation with SY can improve lactation performance, antioxidant status, and immune responses in lactating donkeys, and the recommended dose of SY was 0.3 mg/kg.

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 yr of BW ± SD), weight (250.06 ± 25.18 kg), DIM (39.11 ± 7.42 d), and average 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 wk for adaptation, and 8 wk for collecting data and samples. The results showed that supplementation of donkey diets with AOCP increased lactation performance, including DMI, milking yield, estimated milk yield, solids-corrected milk, ECM, milk fat yield, milk protein yield, milk lactose yield, milk TS yield, and milk SNF yield. The digestibility of DM, CP, ADF, and NDF was increased in the AOCP group compared with the CON group. The AOCP group increased the concentrations of IgA, IgG, and IgM, the activities of the superoxide dismutase, catalase, and total antioxidant capacity in the serum. Artemisia ordosica crude polysaccharides 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, lysophosphatidylcholine (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.

This study evaluated the effects of dietary selenium (Se) supplementation on lactation performance, milk fatty acid composition, and rectal microbiota and short-chain fatty acids in lactating Dezhou donkeys to determine the optimal dose. Twenty-four lactating Dezhou donkeys (estimated milk yield: 3.60 ± 0.84 kg/d; days in milk: 39.93 ± 7.02 d; body weight: 247.24 ± 26.27 kg; parity: 2.82 ± 0.48) were randomly divided into four groups (n = 6): CON (0 mg Se/kg DM), Se1 (0.15 mg Se/kg DM), Se2 (0.3 mg Se/kg DM), and Se3 (0.5 mg Se/kg DM), and were supplemented with Se yeast in the basal diet. The results showed that plasma Se concentrations increased dose-dependently. The Se2 group significantly increased milk yield, milk component yield, milk protein production efficiency, milk production efficiency, the digestibility of acid detergent fiber and neutral detergent fiber, protein biological value, and nitrogen metabolic rate, as well as the proportions of C18:1c9, C18:2c6, unsaturated fatty acids, monounsaturated fatty acids, polyunsaturated fatty acids, n-3 long-chain polyunsaturated fatty acids, the ratio of unsaturated to saturated fatty acids, the ratio of polyunsaturated to saturated fatty acids (P/S), desirable fatty acids, and (C18:0 + C18:1)/C16:0 in donkey milk, while decreasing the proportion of saturated fatty acids, atherogenicity index, and thrombogenic index. The Se2 group also increased acetate and butyrate in rectal feces, and promoted the growth of beneficial bacteria, including Christensenellaceae R-7 group, Lachnospiraceae XPB1014, and norank_f_Erysipelotrichaceae. In summary, the effects of Se supplementation were dose-dependent: 0.3 mg Se/kg DM improved milk performance and optimized milk fatty acid profiles by improving nutrient digestion and metabolism and modulating rectal bacteria structure, whereas 0.5 mg Se/kg DM showed no lactation benefits (with potential inhibitory effects) despite improving the P/S ratio and reducing the atherogenicity and thrombogenic indices.

Donkey meat is valued for its high protein, unsaturated fats, and low cholesterol. Fatty acid (FA) composition critically influences meat quality and is modulated by dietary energy levels. Twenty-four meat donkeys (male) were randomly divided into three groups: a low-energy group (LEG), a medium-energy group (MEG), and a high-energy group (HEG). The trial lasted for 135 days, with dietary digestible energy levels adjusted during the pre-fattening, mid-fattening, and late-fattening phases according to the experimental design. The results showed that MEG and HEG interventions significantly upregulated tissue polyunsaturated fatty acid (PUFA) and n-3 PUFA content while reducing n-6/n-3 ratios, concomitant with enhanced activity and gene expression of most lipid-metabolizing enzymes. Notably, MEG further elevated antioxidant enzyme activities and anti-inflammatory mediators while suppressing pro-inflammatory factors. MEG and HEG significantly upregulated serum cholestane-3,7,12,25-tetrol-3-glucuronide and cortisol, along with hepatic choline, lysoPC(20:2(11Z,14Z)), glycocholic acid, and cholestane-3,7,12,25-tetrol-3-glucuronide. These modified metabolites were predominantly enriched in key metabolic pathways: pentose and glucuronate interconversions, primary bile acid biosynthesis, steroid hormone biosynthesis, glycerophospholipid metabolism, purine metabolism, and glutathione metabolism. Additionally, compared to HEG, MEG improved the antioxidant activities and immune signaling molecule levels with elevated pyroglutamic acid, glutathione, choline, inosine, adenine, and uric acid. Thus, moderately elevated dietary energy levels may enhance FA profiles in muscular and adipose tissues through coordinated regulation of lipid-metabolizing enzymes and associated gene expression, with serum and hepatic metabolites actively participating in these regulatory pathways. However, excessive energy intake could induce oxidative stress in donkeys.

Parturition is a critical event in the reproductive cycle of dairy animals, accompanied by multiple physiological changes in sex hormones, metabolism, antioxidant capacity, and immune function. However, the changes in the rectal microbiota and metabolic products of Jennies from late gestation to parturition affect serum antioxidant capacity and anti-inflammatory responses, but it is still unclear. The present study aimed to investigate the serum antioxidant capacity and anti-inflammatory responses of Dezhou donkeys from late gestation to parturition by analyzing rectal microbiomes and serum metabolomics. Nine pregnant multiparous Dezhou Jennies, aged 6.0 ± 0.1 years, with a body weight of 292 ± 33 kg, an average parity number of 2.7 ± 0.1, and similar expected dates of confinement (35 ± 4 days), were selected for this study. The study investigates the changes in antioxidant capacity and inflammatory responses, as well as the alterations in rectal microbiota structure and serum metabolites, in Jennies at 35 days prepartum (B1), 7 days prepartum (B2), and at 0 h postpartum (B3). The results showed that from groups B1 to B2, serum activity of GSH-Px, IL-10, and GLU concentrations were decreased significantly. In contrast, the concentrations of MDA, IgG, LF, IL-1β, IL-2, IL-6, TNF-α, and ROS increased significantly. From groups B2 to B3, serum activities of GSH-Px, CAT, SOD, and T-AOC, as well as the concentrations of MDA, IgG, IL-2, AST, ALP, and BHBA, were significantly increased, whereas the concentrations of IL-4, IL-10, and CRE decreased considerably. Therefore, from 35 days prepartum to parturition, Jennies experienced a gradually intensifying oxidative stress and inflammatory states, with the inflammatory response being the most severe at parturition, and with enhanced antioxidant capacity corresponding to increased oxidative damage. Microbiome analysis revealed that the group B1 significantly increased the relative abundance of Prevotella and Fibrobacteres. Group B2 significantly increased the relative abundance of Prevotellaceae_UCG-001, Streptococcus, and Acetitomaculum. Group B3 showed a significant upregulation of the relative abundance of Norank_f__F082, Lachnospiraceae_UCG-009, and Prevotellaceae_UCG-004. At the same time, metabolomics analysis revealed that, compared with group B1, group B3 may alleviate inflammation and enhance the body’s antioxidant function by upregulating the tryptophan and arginine metabolic pathways and enriching the differential metabolites (L-tryptophan, L-kynurenine, 3-Indoleacetonitrile, N-acetylglutamic acid). Concurrently, the elevation of these differential metabolites may be associated with the relative abundance of the beneficial bacterium Lachnospiraceae_UCG-009. However, the increase in LysoPC, a fatty acid oxidation product in glycerophospholipid metabolism, as well as the correlation between the sucrose content in the galactose metabolic pathway and the abundance of Paracoccus, indicates the reason why the Jennies are in a state of oxidative stress. Furthermore, group B1 may enhance the serum anti-inflammatory response in Jennies during late gestation by increasing the levels of estrogen in the steroid hormone biosynthesis metabolic pathway. These results could provide useful information for improving the health levels at the specific physiological stages and processes in Dezhou donkeys.

Our study investigated the improved nutritional quality and physicochemical properties in meat, as well as growth performance and antioxidant capacity in meat donkeys, from dietary selenium (Se) yeast (SY), modulating cecal microbiota and multi-omics profiles. A total of 16 one-year-old male meat donkeys (120 ± 25 kg) were allocated to two groups: SS (0.3 mg/kg inorganic Se from sodium Se) and SY (0.3 mg/kg organic Se from SY). SY supplementation significantly increased Se and crude protein content, water-holding capacity, and cooking loss, but reduced ether extract content, shear force, and drip loss of donkey meat; SY also improved body weight, nutrient digestibility, beneficial bacteria (Agathobacter, Lactobacillus), and antioxidant enzyme activities, while reducing pro-inflammatory cytokines and malondialdehyde. Metabolomics revealed upregulation of sphingosine-1 phosphate (S1P), and transcriptomics identified enrichment of the PI3K-Akt pathway. Validation confirmed that SY elevated S1P levels and upregulated S1P receptor 2 (S1PR2) and PI3K-Akt-related genes. In conclusion, meat quality and antioxidant capacity were enhanced, and cecal microbiota in donkeys were reshaped by dietary SY. These findings indicate that dietary selenium supplementation increases Se deposition and improves the quality of donkey meat, providing a promising approach for the development of Se-enriched, value-added functional donkey meat products and processed meat items.