How Is Echinacea Purpurea Extract Used in Animal Feeding?

Echinacea, also known as purple cone flower, echinacea, or purple echinacea, belongs to the Asteraceae family of Echinacea genus and is a perennial herb, most of which are drought-resistant. Echinacea is a well-known medicinal herb in North America with a long history of medicinal use[1]. It is one of the most popular herbs on the international herbal medicine market. Echinacea purpurea, Echinacea angustifolia and Echinacea pallida are the three most commonly used medicinal varieties. Echinacea has a complex of active ingredients, which are mainly involved in immune regulation, relieving oxidative stress, anti-inflammatory and antibacterial, antiviral, anti-tumor, protecting the liver, regulating glycolipid metabolism and healing wounds [2-4]. With the successful introduction around the world, scientists have continued to explore the potential mechanisms of the biological activities of Echinacea and its extracts, and to study their positive effects in alleviating various diseases. Echinacea has been widely used in the treatment of various diseases, such as respiratory diseases, immune deficiency-related diseases, diabetes, depression and cancer [4-6]. Therefore, Echinacea has high research value.

The animal husbandry industry is of great importance worldwide and is an important part of the agricultural sector. Echinacea and its extracts have been widely used in research on feed additives. Many studies have shown that Echinacea and its extracts can improve the immune function and disease resistance of animals by regulating their immune systems. In addition, Echinacea and its extracts can also promote animal growth and development and improve meat quality. These studies indicate that Echinacea and its extracts have broad application prospects in animal production. The exact mechanism by which Echinacea exerts its effects in animal production is currently unclear. Nevertheless, Echinacea is well tolerated and adverse reactions are rarely reported. The author briefly summarizes the main chemical components of Echinacea, focusing on the biological activities and mechanisms of action of Echinacea and its extracts, as well as recent research progress in their application in livestock and aquaculture. The future research direction of Echinacea and its extracts in aquaculture is also prospected, providing a theoretical reference for further broadening their application in the field of livestock and aquatic animals.

1 Chemical components of Echinacea

vary in different species, different parts of the same species, at different growth stages, and even during drying or storage. It is generally believed that the activity of Echinacea is not determined by a single component or a single component. For example, the main components such as high molecular polysaccharides and glycoproteins, as well as low molecular alkanoylamine compounds and caffeic acid derivatives (CADs), all contribute to its biological activity.

1. 1 High molecular compounds

Polysaccharides are complex carbohydrate polymers composed of multiple monosaccharides. From the aerial parts of Echinacea purpurea, methylglucuronic acid arabinogalactan (35 000 u), inulin (6000 u), acidic rhamnose arabinogalactan (450 000 u) and xyloglucan (79 000 u) can be obtained, which have immunomodulatory and anti-inflammatory activities [7]. Glycoproteins are protein and carbohydrate chains that play a role in a variety of physiological activities, including immunology [8]. The glycoprotein obtained from the roots of Echinacea purpurea consists mainly of arabinose (85.8%) in its sugar part, while the protein part is rich in hydroxyproline, serine, alanine, threonine, glutamic acid, aspartic acid and glycine.

1.2 Low molecular weight compounds

1. 2. 1 Alkylamides

Alkylamides, known for their anti-inflammatory activity, are mainly found in the roots of Echinacea purpurea, and are lipophilic, non-polar actives that have been shown to possess high bioavailability and immunomodulatory properties[8] . At least one alkylamide has been identified in Echinacea purpurea[9], including isomers [10]. Alkylamides are mainly isobutylamides of C11-C16 straight-chain fatty acids with an alkene or alkynyl bond, and higher concentrations of isobutylamides affect the anti-inflammatory properties of Echinacea [11].

1. 2. 2 CADs 

The ethanol extract of the above-ground parts and roots of Echinacea purpurea contains CADs, which are hydrophilic polar compounds that mainly include chrysanthemum acid, caffeic acid, chlorogenic acid, etc. CADs, as phenolic compounds, mainly exhibit antioxidant activity. In addition, CADs also exhibit antiviral [12-13] and apoptosis-regulating [14-15] properties. The bioavailability of CADs is poor compared to that of alkamides [16]. Relevant studies have shown that that several CADs can act synergistically to participate in immune regulation [17-19], or with alkylamides, polysaccharides, etc., to participate in the immune regulation response caused by Echinacea administration, thereby enhancing its efficacy.

2 Biological activity of Echinacea and its extracts

2. 1 Anti-inflammatory and immune regulation

Inflammatory reactions have a significant impact on the development of various diseases. Echinacea has been used as an immunomodulator since 1913, and numerous studies have reported its beneficial effects on the immune system and human health. Its various chemical components can stimulate and induce immune response signals, thereby exerting anti-inflammatory effects. Echinacea and its extracts exert a nonspecific immunomodulatory effect by influencing the number of immune cells, granulocyte migration, macrophage phagocytosis, natural killer cell cytotoxicity and cytokine production [20-23]; It can also enhance the body's disease resistance through a specific immune pathway that matures dendritic cells and thus promotes the proliferation and differentiation of T cells [24]. In addition, it may also affect the human immune system through voltage-gated sodium channels [1].

Studies have compared the effects of the three main components of Echinacea, namely alkylamides, CADs and polysaccharides, on specific immune regulation. The results show that CADs are most effective at enhancing the proliferation of splenic lymphocytes and promoting the production of gamma-interferon (IFN-γ) in mice[9] . Among them, the immunomodulatory pathway induced by CADs may be through phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt), NF-κB, MAPK signaling pathways [25] and Toll-like receptor 4 (TLR4) signaling pathways to inhibit inflammatory responses [26], as shown in Figure 1.

However, some studies have found that the lipophilic extract of Echinacea is more effective in immunomodulation than the hydrophilic extract. As a lipophilic substance, alkyl amides can activate the endocannabinoid receptor type 2 (CB2), which may be one of the mechanisms by which it exerts its immunomodulatory properties[27] . Specifically, alkamides may be involved in anti-inflammatory and immunomodulatory effects by regulating signal pathways such as cyclic adenosine monophosphate (cAMP), p38/MAPK, c-Jun N-terminal kinase (JNK), extracellular signal-regulated kinases 1 and 2 (ERK1/2), signal transducer and activator of transcription 3 (STAT3) and NF-κB and other signal pathways, which are involved in anti-inflammatory and immune effects, including the mediation of cytokine, cyclooxygenase and lipase activity [28-30].

In fact, the immunomodulatory properties of both the alkylamides and CADs in Echinacea have been extensively studied and are well explained. In recent years, research on the immunomodulatory potential of Echinacea polysaccharides has gradually increased [31]. It has been reported that polysaccharides act on nonspecific immunity in vivo and in vitro, which can enhance macrophage activity and activate cytokine production [32]. Studies have shown that Echinacea polysaccharides may exert their immunomodulatory effects by regulating the TLR4/NF-κB signaling pathway to alter the production of specific cytokines (Figure 3) [32-33]. There are also other components such as Echinacea purpurea triterpenes E that can also exert anti-inflammatory effects through the NF-κB signaling pathway [34].

The above studies have shown that although the mechanisms by which different components of Echinacea exert anti-inflammatory and immune effects are complex, NF-κB is a relatively common signaling pathway. However, many current studies only extract a single component or a component of Echinacea to explore its potential molecular mechanism. The connection between the combination of multiple components is still unclear, and whether there is a synergistic or antagonistic effect remains to be further studied.

2. 2 Antioxidant

As a natural antioxidant that is non-toxic or has mild toxicity, Echinacea and its extracts have better lipid peroxidation effects than synthetic antioxidants. It can inhibit oxidation in the body indirectly by chelating transition metals[35], providing electrons or hydrogen atoms, or directly scavenging free radicals[36], and acting on enzymes associated with free radicals. The absence of pro-oxidant activity in the presence of transition metals suggests that the chelating properties of Echinacea ingredients appear to have a greater effect on reducing lipid peroxidation than their reducing capacity [37]. In addition, Echinacea and its extracts may also reduce oxidative stress by indirectly increasing a variety of antioxidant enzymes, thereby effectively preventing free radical-induced damage.

Many studies have shown that the specific mechanism by which Echinacea and its extracts exert their antioxidant effect may be through activation of the Nrf2-Keap1 pathway and peroxisome proliferator-activated receptor gamma (PPARγ), as well as inhibition of the expression of phosphorylated JNK (p-JNK) and Keap1, increase the expression of Nrf2, B-lymphoma-2 (Bcl-2) and heme oxygenase-1 (HO-1), quinone oxidoreductase-1 (NQO-1) and other antioxidant enzymes, inhibit Bcl-2-associated X protein (Bax), cytochrome c (Cyto C) and caspase-3 (Caspase-3), thereby inhibiting the mitochondrial apoptosis signal pathway in response to oxidative stress [38-40]. In summary, Echinacea and its extracts exert antioxidant effects through different mechanisms to prevent free radical damage and improve the oxidative stress status of tissues or the body (Fig. 4).

2. 3   Bacteriostatic

Antibiotic resistance has driven the development and utilization of natural plant substitutes. It has been reported that three medicinal Echinacea species are currently used as antibacterial herbs that can inhibit Staphylococcus aureus, Pseudomonas aeruginosa and Listeria monocytogenes [7,21,41-42]. However, Snowden et al. [43] showed that Echinacea ethanol extract did not have antibacterial activity against Staphylococcus aureus. This may be due to differences in the species of echinacea, the plant parts, the extraction process and the resulting chemical composition. In addition to being used alone, echinacea extracts also have antimicrobial activity in preparations combined with other plants. As an herbal mouthwash, preparations containing echinacea extract have an antibacterial effect on cariogenic bacteria and Candida albicans, with minimal cytotoxicity, and are superior to the extract alone [41]. Homeopathic products containing echinacea and astragalus, among others, can reduce the bacterial load in the intestines of dogs, thereby reducing the risk of E. coli infection [44]. In summary, there is relatively little research on the antibacterial properties of the entire Echinacea herb. Most studies focus on the antibacterial activity of Echinacea extracts and mixed preparations, which have been used to treat bacterial and fungal infections and prevent the development of antibiotic resistance, which is beneficial to animal health.

In addition to the common anti-inflammatory, antioxidant and antibacterial activities, Echinacea and its extracts have also been shown to have antiviral, antitumor, liver protection, and regulation of lipid metabolism effects [45-49].

3 Application of Echinacea extracts in animal farming

Echinacea and its extracts have been widely studied as a good immunomodulator in the immune function of animal bodies. They have been used in animals such as mice[50], dogs[44], fish[51], chickens[52], ducks[53], pigs[54], horses[22], cows[55] and humans[56]. In animal husbandry, the application of Echinacea and its extracts has a certain effect on improving animal production performance, regulating immune responses, and enhancing disease resistance.

3. 1 Application in poultry production

Echinacea and its extracts are used as feed additives, which have a significant effect on improving poultry production performance and immune responses.

In terms of production performance, the addition of Echinacea and its extracts to the feed or drinking water can improve indicators such as body weight, meat quality, and egg production performance. Hashem et al. [57] selected 81-day-old broilers and added 5 mg/kg of Echinacea extract alone to the feed. in addition to healthy chickens, the body weight of chickens infected with Escherichia coli also increased significantly. Behboodi et al. [58] added 0.25 and 0.5 mL/L of a mixture containing Echinacea to the drinking water of 300-day-old broilers and found that body weight and feed intake increased significantly. Adding 0.1% to 2.0% Echinacea powder to the feed of 1-day-old broilers significantly improved the meat quality of the chicken breast and thigh meat at 35 days of age and had a significant effect on the meat color index [52]. It can be seen that the addition of echinacea and its extracts can have a positive effect on the quality of poultry carcasses under different addition methods (alone or mixed) and different feeding methods. Adding 2.5, 5.0, and 7.5 g/kg of Echinacea powder to the basic diet of ducks can improve the sperm quality of male ducks, increase fertilization and hatchability, and improve the egg-laying performance of female ducks, thereby increasing feeding efficiency [53].

Luo Junfeng et al. [59] selected one-day-old broilers and added 1.0 and 2.0 kg/d Echinacea granules (with 0.58% inulin content) to each ton of feed. After that, the average feed consumption and feed conversion ratio decreased, not only improving production performance, but also significantly improving the survival rate, which produced significant economic benefits. Therefore, the addition of echinacea and its extracts can improve the production performance of poultry, thereby improving production efficiency, improving product quality, and achieving higher profitability.

Echinacea and its extracts also affect the hematological and biochemical indicators related to immunity in poultry to varying degrees. In 1989, Schranner et al. [60] first reported that the administration of a compound drug containing echinacea extract to healthy chickens resulted in an increase in serum immunoglobulin concentrations. Awad et al. [53] found that Echinacea as a feed additive can lower the ratio of heterophils to lymphocytes (H/L) in the blood, and increase the levels of hemoglobin (Hb), red blood cell (RBC) and white blood cell (WBC) levels increased; serum globulin (Glb) levels increased and albumin/globulin ratio (A/G) decreased; liver function-related aspartate aminotransferase levels decreased; blood lipid and antioxidant levels improved.

The changes in indicators measured by Behboodi et al. [58] and Hashem et al. [57] were basically similar. Behboodi et al. [58] fed a mixed preparation containing Echinacea to broilers through drinking water, which resulted in a decrease in serum H/L, an increase in Hb, RBC, WBC content and hematocrit (HCT), and a decrease in triglycerides, cholesterol and low-density lipoprotein.  HCT) increased, and the levels of triglycerides, cholesterol, and low-density lipoproteins decreased. This indicates that a mixture containing echinacea may have immunomodulatory and metabolic effects. Heshem et al. [57] found that feeding E. coli-uninfected chickens with Echinacea extract powder increased their serum globulin levels and decreased their albumin/globulin ratio. In addition, the aspartate aminotransferase, alanine aminotransferase and glutamyltransferase levels in the serum of healthy chickens and infected chickens decreased, lysozyme increased significantly, indicating that Echinacea extract enhanced the immune response of healthy chickens and reversed the adverse hematological and serum biochemical effects caused by E. coli infection. These blood index results to some extent reflect the improvement of the immune status of the body by Echinacea and its extracts. In addition to studies on healthy birds, some researchers have also explored the immunomodulatory effects of echinacea and its extracts on immunosuppressed birds by constructing a cyclophosphamide (CTX)-induced immunosuppression model.

Immunosuppression can have a suppressive effect on the average body weight and immune organ development of birds, and lead to varying degrees of changes in serum cytokine levels. Ji Yanju et al. [61] gave chicks that had been injected with CTX (100 mg/kg) into the chest for 3 consecutive days Echinacea purpurea whole plant (1% in the diet), and found that Echinacea purpurea significantly increased the expression levels of inflammatory factors such as interleukin-2 (IL-2), IL-4, IL-6, IFN-γ and other inflammatory factors and the expression levels of TLR family related proteins were significantly increased, and the change in spleen index caused by immune suppression was reversed, effectively alleviating the pathological damage to the spleen caused by CTX. This is consistent with the results reported by Yao Lili et al. [62] and Song Hongwei et al. [63], who found that drinking or gavage of Echinacea purpurea extract can increase the organ coefficient of animals, reduce the damage to immune organs caused by CTX injection, improve the immunosuppressed state of cellular and humoral immunity, and increase the content of IL-2 and IL-6. In contrast, Liu Xiyu et al. [64] did not obtain the same results in their study. It is possible that the combination of the Echinacea and astragalus polysaccharide doses in their study was not designed properly or that the dosing regimen was too short, among other reasons, which resulted in a difficult immune effect.

Echinacea and its extracts have immunomodulatory effects, which enable the body to produce a good immune response to different diseases. They can be used to prevent diseases such as coccidiosis, Newcastle disease and infectious bursal disease. The level of antibody titer directly reflects the body's humoral immune status.

Hu Shihui et al. [65] added a compound Chinese medicine containing 20% echinacea (5, 10, 15 g/kg) to the feed to improve the antibody titers of chickens after vaccination with Newcastle disease vaccine, and promote the development of immune organs and the proliferation of splenic lymphocytes and secretion of cytokines. Stressful conditions may lead to immunosuppression and increase the risk of viral infection. Eladl et al. [66] added a commercial product containing Echinacea purpurea extract to the drinking water (10 mL/L) of chickens stressed by dexamethasone (DEX), which enhanced the immune response of the stressed chickens after vaccination with the H9N2 subtype of avian influenza virus. increasing the post-vaccination protection rate, HI antibody titer and heterophilic cell phagocytic activity, and reducing the pathogenicity of H9N2 virus infection. These studies show that Echinacea and its extracts have immunomodulatory effects, can enhance the immune effect of vaccines, and can be used as a safe alternative agent for controlling poultry diseases, which helps reduce poultry mortality and improve the economic benefits of the breeding industry.

In summary, there have been many reports on the effects of echinacea and its extracts, used alone or in combination, on the productivity and immunity of poultry, but these mainly involve chickens [67-69], and there have been fewer studies on other poultry. At the same time, the combined use of echinacea and its extracts requires further investigation.

3.2 Application in pig production

There have been relatively few studies on Echinacea and its extracts in pigs, mainly focusing on immune function.

Some studies have found that adding Echinacea and its extracts to the feed at an additive level of 0.5% to 1.8% can effectively increase the daily weight gain of pigs and reduce the feed conversion ratio, thereby promoting the growth and development of pigs [70-72]. However, another study found that adding 2% or 4% Echinacea powder to the feed did not promote pig growth [73]. The alkaloid echinacoside produced during the metabolic process of Echinacea may be converted into caffeine, which can cause a decrease in appetite. This may be one of the reasons for the difference in animal growth effects. It is worth noting that no growth difference was observed between PRRSV-infected and uninfected animals in this experiment, which may be due to the fact that the pigs in the experiment were in good health before infection, making it difficult for the immune potential of Echinacea to come into play.

In terms of immune function, Echinacea and its extracts are beneficial in raising the levels of immune-related proteins in pig serum and cytokines such as tumor necrosis factor-alpha (TNF-α) and IL-2. Liu Rongsheng [70] found that Echinacea compound ultrafine powder can increase the immunoglobulin content of weaned and suckling piglets and increase the levels of cytokines such as IL-2, IL-10 and IFN-γ. Similarly, Li Quancheng [71] found that adding echinacea extract increased the level of immunoglobulin in piglet serum. In addition, it has been pointed out in some studies that the addition of 1.8% Echinacea ultrafine powder to the feed not only increased the levels of immunoglobulins (IgM, IgA, IgG) and complement C3, but also improved diarrhea, thereby enhancing the body's immune function [72]. Many studies have further explored the effects of Echinacea and its extracts on the antibody levels of pigs after vaccination against common diseases. For example, in a study by Ma Shaopeng et al. [74], Echinacea compound was added to piglet feed at different doses (0.5%, 1.0%, 1.5%), and vaccinated against porcine reproductive and respiratory syndrome (PRRS) at 20 and 50 days of age. The results showed that after the first immunization, the cellular immune function of the pigs improved, and the conversion rate of T lymphocytes increased significantly. After the second immunization, the proportion of qualified antibody titers increased, and the humoral immune function was enhanced.

In addition, the consumption of Echinacea has been shown to effectively promote the production of antibodies against swine fever and swine erysipelas [51, 75]. Although the above studies show that Echinacea and its extracts have a positive effect on enhancing the immune response and improving the disease resistance of pigs, there are also individual studies that suggest that Echinacea and its extracts have limited efficacy in disease treatment. Hermann et al. [70] fed Echinacea root to pigs one week before they were infected with PRRSV, but no antiviral effect against PRRSV or enhanced immunity was observed. This may be related to the fact that the pigs were in good health and they were not infected with secondary pathogens. In the process of intensive animal farming, various diseases caused by oxidative stress in the intestine have a significant impact on animal husbandry. Echinacea extract exhibits protective effects against oxidative stress in porcine small intestinal epithelial cells, which helps reduce the harm of related diseases [76], and has the potential to become an intestinal antioxidant. There have been relatively few studies on the effects of echinacea and its extracts on the intestinal health of pigs, and it is necessary to further explore their potential research value.

3. 3 Application in aquatic animal production

Echinacea and its extracts have a positive effect on the production performance, antioxidant capacity and immune function of aquatic animals.

Fish growth is directly affected by the composition and quality of the feed. Echinacea and its extracts have a varying degree of effect on the growth performance of gray mullet [77], rainbow trout [78], hybrid snakehead [79], carp [80], and Pengze crucian carp [81]. However, there are also different results: In one study, echinacea and its compound extract were added to the feed and extruded into feed pellets for feeding. It was found that there was no significant change in the growth-related indicators such as survival rate, weight gain rate, specific growth rate and fullness of tilapia[79]. This may be related to the species of animal, and the form of the additive (e.g., granular or liquid) may also affect the results. Therefore, further research is needed to determine the mechanism by which the specific components of Echinacea purpurea and its extracts promote the growth of aquatic animals.

Echinacea and its extracts have been shown to increase the phenolic compound content of feed, thereby enhancing its antioxidant activity [51]. Tang et al. [82] found that adding 1% Echinacea purpurea extract to the feed of hybrid snakehead fish significantly enhanced the expression of 10 miRNA families (miR-125, miR-1306, miR-138, etc.) with antioxidant target genes in the head kidney, liver, and spleen tissues. In addition, Yao et al. [79] showed that the addition of 0.4% Echinacea purpurea extract and 0.5% Echinacea purpurea compound extract to the basal diet could increase the antioxidant response in the serum and liver of tilapia and hybrid snakeheads, respectively. Tang Xuelian et al. [81] further pointed out that Echinacea purpurea extract can increase the activity of a variety of antioxidant enzymes in the serum of Pengze crucian carp, while reducing the levels of malondialdehyde and hydroxyl radicals. Overall, these findings highlight that Echinacea purpurea extract can help to a certain extent to enhance the antioxidant capacity of different types of aquatic animals, maintain cell health and overall physiological function. However, it is worth noting that previous studies have found that in carp, feeding a high dose (400 mg/kg) of Echinacea extract significantly reduced serum superoxide dismutase activity [80]. This difference may be due to the fact that the high amount of the additive caused damage to blood cells, which in turn caused a decrease in the body's antioxidant capacity.

Echinacea and its extracts have a significant effect on improving the blood biochemical parameters of aquatic animals. Oskoii et al. [78] found that adding 0.25, 0.5, 1, or 2 g/kg of echinacoside extract to rainbow trout feed increased RBC, Hb, and HCT levels, while also increasing albumin (Alb), globulin (Glb), and total protein levels. albumin, Glb and total protein levels. Similar results were also verified in a study by Akbary et al. [77], who added 50, 100 and 200 mg/kg Echinacea purpurea leaf extract to the diet of grey mullet and also observed similar changes in blood indicators. This indicates that Echinacea and its extracts may help improve the blood health of aquatic animals and have a positive regulatory effect on their biochemical parameters. The immune system of fish mainly depends on non-specific immunity, and the addition of Echinacea and its extracts to the feed has been shown to be an effective way to improve the immune function of fish.

Early studies found that Echinacea extract can significantly increase the lysozyme activity in carp serum, as well as the phagocytic activity and phagocytic index of WBC, effectively enhancing the resistance of fish to bacteria [80]. Akbary et al. [77] further supported this finding in their study, in which they added 200 mg/kg Echinacea purpurea leaf extract to the diet of gray mullet, significantly increasing lysozyme, phagocytic activity and respiratory burst activity, while reducing mortality after bacterial infection, thereby improving the immunity of gray mullet. In addition, Abdel et al. [83] showed that the phagocytic activity and phagocytic index of macrophages in the blood of Nile tilapia fed 500 mg/kg Echinacea extract were also significantly increased. It can therefore be concluded that the addition of Echinacea extract to the feed helps to enhance the immune response in fish of different species. In addition, Echinacea and its extracts have a positive effect on the expression of non-specific immune factors in different tissues of aquatic animals.

While discussing blood biochemical parameters, the importance of the immune system should not be overlooked. Yao et al. [79] showed that the addition of 1% Echinacea purpurea and its compound extract to hybrid snakeheads significantly up-regulated the expression of glutathione peroxidase and lysozyme in the spleen. The compound extract also significantly up-regulated the expression of IL-10 in the spleen. Abdel et al. [83] found that the addition of 500 mg/kg Echinacea purpurea extract alone could significantly upregulate the expression of the IL-1β gene in the head kidney tissue of Nile tilapia, and the addition of Echinacea purpurea extract in combination with vitamin C could also significantly upregulate the expression of the TNF-α gene in intestinal tissue. The results of a study by Qin Zhihua et al. [84] showed that intramuscular injection of 10, 20, or 40 mg/mL Echinacea purpurea extract significantly affected the relative expression of lysozyme and transferrin genes in the head kidney tissue of turbot, and also significantly affected the relative expression of transforming growth factor β1, IL-1, and C3 complement genes. In addition, Tang et al. [82] further showed that Echinacea purpurea extract can affect the immune activity of fish through miRNA regulation, providing new ideas for in-depth exploration of the role of miRNAs in the immune system of fish.

In summary, Echinacea and its extracts have immunomodulatory and antioxidant activities, and have the potential to be used as natural immune stimulants in aquaculture. However, in recent years, there has been limited research on the application of Echinacea and its extracts to aquatic animals in China. Further research is needed to expand the scope and depth of research and explore the potential application of Echinacea and its extracts to aquatic animals other than fish.

3. 4 Application in ruminant production

There is currently not much research on Echinacea and its extracts in ruminants, but some studies have shown that Echinacea extracts have a certain degree of effect in improving production performance, relieving oxidative stress and enhancing immunity.

Some studies have shown that Echinacea extracts have no significant effect on production performance indicators such as body weight gain and feed conversion ratio in ruminants [85-88]. However, Yang Guofeng et al. [89] found that after adding 1.2% compound echinacea extract to the concentrate, the final weight and average daily weight gain of the milk goats increased significantly, and the feed conversion ratio decreased extremely significantly, which improved the production performance to a certain extent. The differences in the test results may be attributed to a variety of factors such as the species, age, dosage and duration of the test.

Merati et al. [90] first applied Echinacea purpurea extract to the cryopreservation of ram sperm, and the results showed that it significantly improved the integrity of the sperm acrosome and the state of lipid peroxidation. In addition, the cleavage rate of mature oocytes inseminated with it increased significantly, indicating that Echinacea purpurea extract can effectively improve the quality and fertility of ram epididymal sperm. This is consistent with the results of Mao et al. [91], which further proves that Echinacea extract, as a natural antioxidant, may help improve animal fertility. Asuncion et al. [85] found that feeding Echinacea extract not only effectively alleviated the weight loss of yaks during the perinatal period, but also reduced the degree of lipid peroxidation in the body after birth and enhanced the antioxidant capacity of yaks.

These studies show that gender differences in different species do not affect the antioxidant effects of Echinacea purpurea extract in ruminants in vivo or in vitro experiments and improve productivity. In terms of changes in serum composition, Echinacea extract can increase the Glb content, reduce the Alb content and urea nitrogen levels, and also increase the activity of alkaline phosphatase (ALP), etc., to maintain the normal metabolism of body substances [85-86,88]. In contrast, Ayrle et al. [87] found that there was no statistically significant change in the IgG concentration in the serum of calves fed 0.5 or 5 g of Echinacea purpurea extract.

Previous studies have also pointed out that Echinacea purpurea extract has no significant effect on the serum ALP activity and IgA and IgG content of rams [89]. The specific reasons for this remain to be further investigated. From the perspective of blood physiological indicators, some studies have found that the addition of Echinacea purpurea extract to the feed can significantly increase the levels of RBC and HCT in goats, thereby promoting the synthesis of Hb and enhancing the function of RBC [86]. However, Aryle et al. [87] did not observe a positive effect of Echinacea extract on the hematopoietic function of calves.

As this is the first in vivo study on the effects of Echinacea extract in cattle, future research may reveal its effects on the immune system of this species. The experiment also further discovered from the perspective of cytokines by testing the gene expression levels of leukocyte inflammatory factors that no significant changes occurred in the mRNA abundance of IL-1β, IL-8, TNF-α and Cox-2, indicating that Echinacea purpurea extract had no significant effect on the above inflammatory markers. However, Seckin et al. [55] found that Echinacea-containing mixtures at different doses may have increased the levels of IgG and IFN-γ in calves by inducing a natural immune response, as well as the gene expression levels of important cytokines (IFN-γ, IL-1β, IL-2, and TNF-α).

These studies suggest that the effect of Echinacea purpurea extract on immune-related functions in animal bodies may vary depending on the species or age of the animal. It is well known that animal diseases are often a direct manifestation of immune dysfunction. In a study, it was found that feeding 0.5 g/d of Echinacea purpurea ethanol extract reduced the duration of diarrhea in calves vaccinated against bluetongue virus by 44% [87].

Liu Zhiying et al. [86] and Song Shuzhen et al. [88] also observed the effective relief of diarrhea by Echinacea extract in test sheep of different breeds. This suggests that Echinacea extract may fight infections by stimulating the local intestinal immune system, thereby enhancing the disease resistance of ruminants. Therefore, the use of Echinacea extract in production practices can improve immunity and reduce the risk of disease in animals.

In summary, Echinacea extract can to some extent promote the improvement of serum biochemical indicators, immune function and reproductive performance of ruminants, thereby potentially improving the economic benefits of farming. However, there are few studies on the application of Echinacea herb in ruminants. The effects and mechanisms of Echinacea and its extracts on the production performance and immune system of ruminants need to be further explored and elucidated.

4 Summary

Echinacea and its extracts have a wide range of biological activities and nutritional value. Domestic and foreign scholars have fully demonstrated the various medicinal values of echinacea and its extracts through in vitro and in vivo experiments, including immune and anti-inflammatory activities, antioxidant activities, anti-viral and anti-bacterial activities, and anti-tumor activities. In the field of animal husbandry, Echinacea and its extracts can produce a variety of positive effects. Not only can they improve animal growth performance, production performance and reproductive performance, improve meat quality, but also adjust the balance of intestinal flora, maintain intestinal health, enhance the efficacy of viral vaccines in animals, thereby improving immunity and reducing disease transmission. These effects help to effectively improve the economic benefits of animal husbandry. However, a few studies have found that Echinacea does not have a positive effect in animal farming. More research is needed to resolve this debate.

There are many directions worth exploring in the application of Echinacea and its extracts in animal husbandry: ① standardizing the application of Echinacea and its extracts to determine the effective form, method of use and appropriate dosage; ② the specific mechanism of the synergistic effect of different active ingredients in Echinacea and the development and utilization of other uncommon active ingredients; ③ exploring the active ingredients that play a major role in Echinacea mixtures; ④ The potential efficacy of Echinacea and its extracts against common pathogens or combinations of pathogens in pigs; ⑤ Correlating the mechanism of action of Echinacea active ingredients with their mechanism of action in animal production; ⑥ In-depth research on the reproductive performance of Echinacea and its extracts in animals; ⑦ The preventive effect of Echinacea and its extracts before the onset of disease; ⑧ Research on the application of Echinacea and its extracts in ruminants and pigs.

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