Antibiotics have bacteriostatic or bactericidal effects. Studies have shown that using appropriate doses of antibiotics in the feed of food animals can prevent animal diseases and improve production performance (1–3). This has been common practice in modern animal husbandry for decades. However, the irrational use of antibiotics has led to the emergence of more and more drug-resistant bacteria. These antibiotic-resistant bacteria remain in animals and are easily passed to humans through the food chain (4), and these antibiotic-resistant bacteria can be pathogenic to humans and widely spread in the environment through animal feces (5), thus affecting animal and human health and food safety. This has raised concerns, prompting efforts to develop so-called alternatives to antibiotics.

At present, the natural antibiotic substitutes found by people are mainly beneficial prebiotics, probiotics, alkaloids, antimicrobial peptides, essential oils, and plant substances, etc. (4, 6–10), the most common feed additives have been widely used in the animal husbandry industry after antibiotic growth promoters were banned. Plant-derived feed additives include herbs, plant extracts (essential oils, oil-based resins, tannins, saponins, polysaccharides, phenols, flavonoids, etc.), and their active ingredients (11–13). As feed additives, these substances can promote the growth of livestock and poultry, increase the feed reward, and improve the immune capacity and antioxidant capacity of the animal body. Olawuwo’s et al. research shows that (14), the powder of Morinda lucida, Acalypha wilkesiana, and Ficus exasperata is higher in macronutrients and micronutrients, such as K, Ca²⁺, Na⁺, Mg²⁺, and P, than the standard broiler feed. It is also rich in organic acids and sugars required for livestock nutrition and can effectively maintain antioxidant defenses. To improve animal health and promote the effect of growth performance. Studies have also shown that the addition of Artemisia lordosica polysaccharide can play an anti-inflammatory and antioxidant role, improve the protein digestibility of broilers, reduce the content of serum stress hormones and pro-inflammatory cytokines, and alleviate the growth inhibition and intestinal damage induced by lipopolysaccharides (LPS) (15). Dietary supplementation of Origanum vulgare and Andrographis paniculata extract (FOA) (16) can reduce feed intake, increase the ratio of beneficial and harmful bacteria in the gut, reduce coccidium oocysts and alleviate intestinal lesions of broilers. To sum up, the plants extract substances added can promote the growth of poultry and intestinal health, improve the body, and improve anti-inflammatory and antioxidant function.

Yupingfeng powder, a traditional Chinese medicine formula, is composed of Astragalus membranaceus, Atractylodes macrocephala Koidz. and Saposhnikovia divaricata (Turcz.) Schischk (17). It has the functions of immune regulation (18), anti-virus (19), anti-tumor (20), and anti-aging (21). Yupingfeng polysaccharide is the main substance in the alcohol-precipitation part of Yupingfeng powder, which has many biological functions such as enhancing the body’s immunity (22), repairing the intestinal barrier (23), and enhancing the body’s antioxidant capacity (24). For example, YPF-P significantly increased the thymus index and promoted the secretion of total antioxidant capacity (T-AOC), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), immunoglobulin A (IgA), immunoglobulin A (IgG) and immunoglobulin M (IgM) and other immune factors and antioxidant factors in the blood (25). The study by Chen et al. also showed that dietary Yupingfeng polysaccharide supplementation could significantly increase the expression of immune-related genes in blood cells and the intestinal tract; In addition, it can also reduce the cumulative mortality of Litopenaeus vannamei after Vibrio harveyi attack (26). The results showed that YPF-P is beneficial to animals, and can play a certain role in immune response, oxidative stress, and intestinal homeostasis of animals. YPF-P is a worthwhile green plant additive.

The gut is the largest body interface in contact with the environment (27), its primary function is to digest and absorb nutrients while forming a barrier against luminal pathogens such as antigenic peptides, bacteria, toxins, parasites, allergens and carcinogens (28, 29). The intestinal tract is rich in microorganisms [~10¹²–10¹³, (30)], mainly composed of anaerobic bacteria, and it is challenging to explore the microbial diversity of healthy intestinal flora using traditional culture methods (31). Guo et al. showed that Lentinus edodes extract (LenE), Tremella fuciformis extract, and Astragalus membranaceus Radix extract could increase the number of potentially beneficial bacteria (Bifidobacterium and Lactobacillus) in chicken cecum microflora while decreasing the number of potentially harmful bacteria (Bacteroides and Escherichia coli) (32), these polysaccharides extracts can be used as regulators of intestinal microorganisms in broilers to promote body health. More recently, natural plant polysaccharides, which are considered quality prebiotics, have been shown to reach the large intestine, where they can interact with the gut microbiota (GM) (33), where they can promote the proliferation of beneficial bacteria and inhibit the overgrowth and reproduction of foreign bacteria and potentially pathogenic bacteria, thereby regulating gut health (34). This study investigated the effects of different concentrations of Yupingfeng polysaccharide as a feed additive on growth performance and intestinal flora of Qingyuan Partridge chickens, aiming to provide the theoretical basis for Yupingfeng polysaccharide as a green and healthy feed additive for the poultry production industry.

In recent years, studies have shown that the extracts of medicinal plant active ingredients, including Chinese herbal polysaccharides, have been playing a positive role in livestock production and disease prevention and treatment (12). Chinese herbal polysaccharide can play a variety of biological functions (36, 37), such as anti-inflammatory (38), anti-tumor (39), antioxidant, lowering blood sugar, lowering blood lipids (40), immune regulation (41), and regulating intestinal flora (42), etc. Chen et al. found that the basal diet supplemented with 1,000 mg/kg Lonicera fulvotomentosa extract could significantly increase the final weight of weaned piglets and the diversity and richness of intestinal flora in the jejunum and rectum. With the increase inf extract concentration (600 mg/kg, 800 mg/kg, 1,000 mg/kg), the diarrhea index of piglets was decreased [p < 0.05, (43)]. Appropriate doses of Piper betel (PB) (4 g/kg) and Persicaria odorata (PO) (8 g/kg) can also be used as growth promoters to significantly increase weight gain and reduce feed reward in broilers while positively regulating intestinal structure (44). Reda observed that adding 750 and 1,000 mg/kg of Licorice (Glycyrrhiza glabra) to the diet of Japanese quails enhanced the growth performance of the animals and reduced intestinal pathogens (45). These results are consistent with our experimental results. In this experiment, when the added amount of Yupingfeng polysaccharide is 8 g/kg, the final body weight, the total weight gain and the average daily gain of Qingyuan Partridge chickens can be significantly improved (p < 0.05), and the feed-to-gain ratio can be significantly reduced (p < 0.05). Therefore, appropriate concentration added to the basic diet of jade screen polysaccharide can improve chicken growth performance.

Growth hormone and insulin-like growth factor are both peptides that can promote growth and play an active role in the body’s growth, development and metabolism. Growth hormone, also known as somatotropin, has widely distributed receptors that stimulate the growth and differentiation of muscle, bone, and cartilage. On the other hand, growth hormone also stimulates the production of insulin-like growth factors (IGFs), which can indirectly mediate many of the growth-promoting effects of growth hormone (46). There are two forms of IGF, IGF-I and IGF-II. Among them, the production of IGF-I is more dependent on GH, and its growth-promoting effect is stronger. Some studies have shown that dietary supplementation of Radix Rehmanniae Preparata polysaccharides (RRPP) can promote and significantly improve growth performance (p < 0.05); the mRNA expression levels of serum growth hormone (GH), insulin-like growth factor IGF-I and IGF-II were significantly increased by RRPP supplementation (47). Similarly, the research of Zhao et al. (48) also has the same conclusion: in early weaned piglets, diets supplemented with different concentrations of Mulberry leaf polysaccharides (MLPs) and antibiotics found that IGF-I and GH levels in Mulberry leaf polysaccharide treated (MT) group were significantly higher than those in control treated (CT) group and antibiotic treated (AT) group (p < 0.05). Ouyang et al. (49) also reported that supplementation with 1.0% and 1.5% Ouyang et al. also reported that supplementation with 1.0% and 1.5% water soluble Alfalfa olysaccharides (WSAP) significantly or extremely significantly increased the expression of GH and IGF-I genes in liver, adipose tissue and kidney of broilers (p < 0.05 or p < 0.01), and improved the growth performance and carcass traits of broilers. In this experiment, the same conclusion was also obtained, when the added amount of YPF-P was 8 g/kg, the expression levels of IGF-I were significantly increased (p < 0.05), and the concentration of GH was not significantly changed, but there was a trend of increase. This is also consistent with our results in the previous part, when the amount of Yupingfeng polysaccharide added to the diet was 8 g/kg, the weight gain of Qingyuan Partridge chicken was the most obvious, and the feed reward was the lowest. Therefore, it was concluded that Yupingfeng polysaccharide could promote growth.

A large microbial community exists in the gastrointestinal tract and these microorganisms play an important role in the growth and health of chickens, promoting the absorption of nutrients and improving the immune system (50). The addition of Chinese herbal ingredients and their derivatives can improve the community composition of intestinal microorganisms of broilers, affect the digestion and absorption of nutrients, and thus affect the growth performance and immune performance of broilers (51–56). α diversity results showed that compared with the control group, there were no significant differences in Shannon, and Simpson indices in the YC group, indicating that adding Yupingfeng polysaccharide did not change the species diversity and richness of intestinal flora. The PCoA map of β diversity results showed that the intestinal flora of the control group and the experimental group were significantly separated, with little overlap, and there was a significant difference between the groups, suggesting that there was a substantial difference in the microbial community between the two groups, and the analysis results were reliable. At the phylum level, Firmicutes, Bacteroidetes, Desulfobacterota, Campylobacter, Actinobacteria, and Proteobacteria were the main microbial groups in the cecum, among which Firmicutes (43.18%) and Bacteroidetes (41.94%) were in the control group, and Firmicutes (55.45%) and Bacteroidetes (25.30%) were in the YC group. Studies by Li et al. showed that Bacteroides, Firmicutes, Proteus, and Ferribacter, accounted for more than 97% of the cecal microbiota of all chickens (57); the top two are Firmicutes and Bacteroidetes, which are consistent with our results. Hou et al. found that in Arbor Acres broilers fed the same diet in FL and LL lines, Firmicutes and Bacteroides accounted for 71.36% and 23.40% of the intestinal flora in fat chickens, 53.44% and 41.09% in lean chickens, respectively (58). Consistent with the findings of Furet and Chika Kasai, non-obese subjects had higher Bacteroides abundances at the phylum level in their gut microbes compared to obese subjects (59, 60). In this experiment, the addition of Yupingfeng polysaccharide tended to reduce the relative abundance of Bacteroidetes, consistent with the study’s results, and the ratio of Firmicutes to Bacteroidetes increased, and the weight of birds increased. At the genus level, the predominant bacteria groups of cecum contents are unclassified_Muribaculaceae, unclassified_Lachnospiraceae, Bacteroides, Lachnospiraceae_NK4A136_group, and unclassified_Oscillospiraceae. Among them, the first three belong to Bacteroides, while the last two belong to Firmicutes and Clostridium. The flora that differed between the CC and YC group were unclassified_Muribaculaceaeand unclassified_Oscillospiraceae. Hu et al. found that Grifola frondosa powder suspension (GFPS, powder of a medicinal fungus with anti-obesity properties) can reduce body weight and increase the abundance of unclassified_Muribaculaceae in the intestinal flora of mice (61), which is exactly consistent with our results. unclassified_Muribaculaceae is a bacterium that produces short-chain fatty acids, which are important in regulating glucose and lipid metabolism. These results indicate that Yupingfeng polysaccharide can regulate the abundance of different intestinal flora by increasing the proportion of beneficial bacteria and reducing the proportion of harmful bacteria to promote the growth performance of chickens.

In summary, this study shows that adding Yupingfeng polysaccharide to the basic diet can improve the growth performance of broilers and have a particular effect on the composition of their intestinal flora. When 8 g/kg Yupingfeng polysaccharide was added to the diet, the final body weight, the total weight gain and the average daily gain of Qingyuan Partridge chickens was increased (p < 0.05), and the feed reward was also decreased (p < 0.05). At the same time, it can promote the expression of GH and IGF-I in serum. Although adding Yupingfeng polysaccharide did not change the diversity and richness of intestinal flora, it could significantly affect the distribution proportion of dominant flora and increase the proportion of dominant flora. This study can provide the basic theoretical basis for utilizing Yupingfeng polysaccharide in broiler production.

The original contributions presented in the study are publicly available. This data can be found at: https://www.ncbi.nlm.nih.gov/bioproject/; PRJNA1067511.

The animal studies were approved by Institutional Experimental Animal Ethics Committee of Foshan University. The studies were conducted in accordance with the local legislation and institutional requirements. Written informed consent was obtained from the owners for the participation of their animals in this study.

YG: Data curation, Formal analysis, Methodology, Writing – original draft. WZ: Methodology, Visualization, Writing – review & editing. YB: Data curation, Writing – review & editing. BW: Conceptualization, Methodology, Project administration, Supervision, Writing – review & editing.