What Are the Uses of Stevia Powder in Animal Feeding?

Stevia is a perennial herb in the family Asteraceae, native to the high grasslands along the border of Paraguay and Brazil in South America. China's stevia production and export volume ranks among the highest in the world, and the planting area is extensive. 2 Stevia was first widely cultivated for the extraction of stevia sugar, which is a glycoside with a sweetness about 300 times that of sucrose but only 1/300 of the calories. Therefore, stevia sugar can be used as a sweetener to satisfy sweetness while reducing the calories consumed by the body. 3

Modern intensive animal production poses challenges to the safety of animal products. How to improve the production of animal products while ensuring the health of animals is one of the research hotspots in the animal husbandry industry. Stevia contains a variety of bioactive ingredients with antioxidant, anti-inflammatory, and antibacterial functions. This paper reviews the active ingredients of stevia and their application effects in livestock and poultry production, with a view to providing a reference for the follow-up research and application of stevia.

1 Main active ingredients of stevia

The main bioactive substances in stevia extract are stevioside, polyphenols, etc.7. Stevioside mainly contains stevioside glycosides, terpenes, monosaccharides and fatty acid glycosides. The main components are rebaudioside A/B glycosides, steviol glycosides and glucose.8. The high performance liquid chromatography method ( HPLC) was used to identify the phenolic substances in stevia. The results showed that the phenolic acid compounds in stevia are mainly isochlorogenic acid A, chlorogenic acid, isochlorogenic acid B, neochlorogenic acid, cryptochlorogenic acid and other substances, and the flavonoids are mainly quercetin-3-0-rhamnoside, rutin, quercetin-7-O-glucoside, luteolin-7-O-glucoside, quercetin-3-O-xyloside, and apigenin-7-O-glucoside. quercetin-7-O-glucoside, luteolin-7-O-glucoside, quercetin-3-O-xyloside, apigenin-7-O-glucoside, apigenin-3-O-xyloside, apigenin-7-O-glucoside, apigenin-3-O-xyloside, apigenin-7-O-glucoside, apigenin-3-O-xyloside, apigenin-7-O-glucoside, apigenin-3-O-xyloside, apigenin-7-O-glucoside, apigenin-3-O-xyloside, apigenin-7-O-glucoside, apigenin-3-O-xyloside, apigenin-7-O-glucoside, apigenin-3-O-xyloside, apigenin- Physiological functions of stevia active ingredients.

2. Stevioside

Stevioside is extracted from the leaves of the stevia plant and is a sweetener obtained through a series of purification processes. The main components, such as the glycosides rebaudiosides A/B, are formed by glycosylation of the stevioside in the plant body under the action of various enzymes”, and have the functions of anti-oxidation, anti-inflammation, antibacterial and anticancer, etc. 12-14].

2. 1.1 Antioxidant

Stevia has a certain antioxidant effect. Some studies have shown that adding Rebaudioside A to carbon tetrachloride-induced human hepatoma cell culture medium can significantly inhibit cell death caused by oxidative stress. It exerts an antioxidant effect by increasing the expression of heme oxygenase (HO-1) and quinone reduction enzyme-1 (NQO-1) expression levels in cells plays an antioxidant role5.

Using a model of oxidative stress damage induced by pretreatment of pigs with stevia and diquat, the activity and proliferation of intestinal epithelial cells was improved, and the production of reactive oxygen species (ROS S) and malondialdehyde (MDA) production, and significantly increased the activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px)6. Stevia therefore improves the body's antioxidant capacity by regulating oxidative stress-related signal pathways. Research found that adding 240 mg/kg stevia to the feed of the medaka fish significantly increased the antioxidant capacity of the fish liver7, and adding stevia to the diet of aging laying hens significantly increased the antioxidant capacity of their reproductive system8.

2.1.2 Anti-inflammatory

Stevia can to some extent increase the levels of nitric oxide (NO) and ROS in the body, thereby playing an anti-inflammatory immune role. Through cell experiments, it was found that adding 200 mg/L stevia to the medium of macrophages can significantly increase the phagocytic activity of macrophages, the concentration of NO and the levels of the cytokines interleukin-1β (IL-1β), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α). levels, and has a strong immunomodulatory effect19.

Stevioside inhibits bone resorption in osteolytic model mice by inhibiting the phosphorylation of protein kinase TAK1, the NF-kB/MAPKs signaling pathway, the formation of osteoclasts, and the expression levels of the inflammatory factors TNF-α, IL-1β, and IL-6. In vitro cell test results show that stevioside stevioside can inhibit osteoclastogenesis by inhibiting the phosphorylation of the three major subfamilies (ERK, JNK and p38) of the MAPK signaling pathway, the expression levels of the main signal regulators (c-Fos) and activator T cell nuclear factor cl, and prevent osteoclast formation 20]. Ri zwan et al. 211 found that feeding 200 mg/kg stevia significantly reduced liver enzyme and serum creatinine levels in rats with gentamicin nephrotoxicity, and alleviated renal tissue damage, inflammation and tubular necrosis. The above results show that stevia can promote the recovery of animal body damage by regulating the expression of immune factors.

2.1.3 Lower blood sugar and blood lipids

Some studies have shown that administering 5 and 10 mg/kg stevioside and steviol, the metabolic product of stevioside, to diabetic mice by gavage can significantly increase the levels of blood glucose and cholesterol (TC) in the serum, thereby significantly increasing the uptake of glucose by the heart and brain and reducing the accumulation of glucose in the liver and kidneys.22,23 This indicates that steviol has the effect of lowering blood glucose in diabetic mice. 23. Adding stevia to the diet of mice with non-alcoholic fatty liver disease can increase the expression of peroxisome proliferator-activated receptor-α and adenosine monophosphate-activated protein kinase-α (AMPK-α) receptor proteins and reduce the expression of sterol regulatory element binding protein 1C protein, thereby improving the symptoms of non-alcoholic fatty liver disease in mice. 24].

2. 1.4 Other effects

In addition to its antioxidant, anti-inflammatory and hypoglycemic and hypolipidemic effects, stevia also has the effect of improving the structure of the intestinal flora in animals and regulating the secretion of neurotransmitters in the brain. Stevia sugar regulates the imbalance of the flora in animals mainly by changing the structure of the intestinal flora. Nettleton et al. 25 found that adding 2 to 3 mg/kg Rebaudioside A to the drinking water of male mice reduced the abundance of Clostridium and Streptococcus in the cecum of male mice and increased the abundance of Gram-negative bacteria and Akkermansia muciniphila. Hu Yu et al. 120 found that intragastric administration of 6.25 mg/kg stevia can reduce the level of glutamate in the brain tissue of depressed mice, and increase the expression levels of γ-aminobutyric acid, dopamine (DA), 5-hydroxytryptamine, albumin D-site binding protein (DBP ), γ-aminobutyric acid B2 receptor, and protein expression of substance P (SP) protein, thereby increasing the sugar water preference rate of depressed mice and reducing the immobile time of mice in forced swimming, indicating that stevia can, to some extent, affect animal mood by regulating the release of neurotransmitters in the brain.

2. 2.2 Stevia polyphenols

Phenolic compounds are a type of plant metabolite. Stevia polyphenols mainly include phenolic acids and flavonoids, which have various biological activities such as antioxidant, anti-inflammatory and antibacterial activities.27-28

2. 2.1 Antioxidant

The phenolic substances in stevia have a significant scavenging effect on hydroxyl radicals, 1,1-diphenyl-2-trinitrophenylhydrazine (DPPH) radicals and ·O₂-free radicals, and this effect is positively correlated with concentration. They have a certain degree of antioxidant capacity. 29-301. Wang Zhiyong et al. 31 found that stevia total chlorogenic acid has strong free radical scavenging and antioxidant abilities; compared with the addition of 0.2% butylated hydroxyanisole, the addition of 0.5% chlorogenic acid to freshly squeezed rapeseed oil resulted in a lower oil acid value.

Similarly the same concentration of chlorogenic acid, cryptochlorogenic acid and sodium ascorbate was added to fish oil, and then oxidation was induced. The results showed that the scavenging ability of chlorogenic acid and cryptochlorogenic acid for DPPH free radicals was higher than that of sodium ascorbate³², suggesting that stevia extract chlorogenic acid has a certain antioxidant capacity and can be used as an antioxidant for lipids. In addition steviol glycosides can also increase the insulin level in the serum of diabetic mice and the activities of glutathione peroxidase (GSH-Px), superoxide dismutase (SOD) and catalase (CAT) in the muscles of flounder33]. Zhou Wei et al. 34 found that daily administration of 200 mg/kg stevia flavonoids by gavage can significantly increase the serum SOD activity of type 2 diabetic mice and significantly reduce the MDA content in the serum, thereby improving the antioxidant capacity of the animal body.

2. 2.2 Anti-inflammatory and antibacterial

The phenolic substances in stevia can reduce the level of pro-inflammatory cytokines in the body and thus have an anti-inflammatory effect.35 Stevia extract containing 1 mg/kg of isochlorogenic acid A and isochlorogenic acid C (>90%) significantly inhibits foot swelling in mice with acute inflammation, increases SOD activity in serum and liver tissue, and reduces the level of prostaglandin E2 (PGE2). D activity and reduce the level of prostaglandin E2 (PEG2); oral administration of 2 mg/kg of chlorogenic acid A and isochlorogenic acid C can significantly increase SOD activity in serum and liver, reduce MDA content, and isochlorogenic acid C can also reduce serum NO and PEG2 levels 36, thereby improving the animal's anti-inflammatory ability. In vitro tests have found that stevia methanol extract has a significant inhibitory effect on the growth of Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, Aspergillus niger and Candida albicans.37 Adding 0.5% isochlorogenic acid or 0.5% sodium diacetate to feed can effectively control mold growth, indicating that isochlorogenic acid has a good antibacterial and antifungal effect.311

2. 2.3 Other effects

In addition to its antioxidant properties, stevia extract also has the effect of regulating the metabolism of animals. Milani et al. 38 found that the use of 0.2% steviol glycosides, which do not contain stevioside, can significantly reduce the blood TG content and serum transaminase activity of mice with diabetes induced by sodium thiopental, and improve the metabolic regulation ability of diabetic mice. Stevia and chlorogenic acid may improve the metabolic dysfunction of skeletal muscle in type 1 diabetic mice by regulating the glucose metabolism of diabetic mice by up-regulating glucose transporter 4 (GLUT4) and adenosine monophosphate-activated protein kinase (AMPK) expression, inhibiting oxidative stress and enhancing the activities of endogenous antioxidants such as SOD, CAT and GSH-Px.33

2. 3 Stevia residue

Stevia residue is an industrial by-product of stevia production. It mainly contains substances such as chlorogenic acid, caffeic acid and quercetin, which have anti-inflammatory, antibacterial, antioxidant, anti-tumor, hypotensive, hypoglycemic and lipid-lowering effects, as well as improving the body's immune system39-43]. The The DPPH method, TEAC method and FRAP method were used to test the antioxidant capacity of stevia residue extracts. The results showed that stevia extracts can all scavenge free radicals and have a certain degree of antioxidant capacity. The overall ranking of antioxidant activity is caffeic acid>quercetin>isochlorogenic acid B>chlorogenic acid>isochlorogenic acid A>isochlorogenic acid C>cryptochlorogenic acid>quercitrin 44].

Some research It was found that the oral administration of 500 mg/kg body weight of stevia residue extract can significantly increase SOD and GSH-Px activity in the serum, liver and brain tissues of D-galactose-induced aging model mice, reduce MDA content, and increase the relative expression of antioxidant antioxidant genes GSH-Pxl, SODI, HO-1 and Nrf2 in brain and liver tissues.1451 The results show that stevia residue extract is beneficial for scavenging lipid peroxides in the serum, enhancing the antioxidant capacity and immune capacity of the animal body, and relieving oxidative stress damage to tissues. Stevia residue extract can also significantly increase the protein kinase pAkt/Akt ratio and Nrf2 and HO-1 protein expression in the livers of mice in a lipopolysaccharide (LPS)-induced oxidative stress model, and reduce the oxidative stress level of the animal body by activating the Akt/Nrf2/HO-1 signaling pathway and increasing the expression level of antioxidant enzymes (SOD, etc.)1461.

In addition to its antioxidant effect, extract, in addition to its antioxidant effect, also has the effect of improving the body's inflammatory response and blood sugar and blood fat. Mehmood et al. 147 showed that the addition of 200 and 400 mg/kg stevia residue extract significantly reduced the activity of intestinal tissue oxidase, alleviated the inflammatory response, and improved the intestinal morphology of the duodenum, jejunum, and ileum tissues in mice. In addition Stevia rebaudiana extract also has a positive effect on fructose PO-induced hyperuricemia by reducing uric acid levels, xanthine oxidase activity, and improving oxidative stress and inflammatory responses in mice.48 Zhao et al.4 found that administration of high-fat and high-sugar-induced

3 Stevia's application in livestock and poultry production

3.1 Stevia's application in pig production

Adding stevia extract and its by-products to the diet can improve the growth performance of piglets, the structure of the intestinal flora, and the quality of local pork. Wang Yuanxiao et al. 50 found that adding 100 mg/kg stevia to the nursing piglet feed can significantly increase the weight of the nursing piglet by 4.7% from 15 to 21 days of age, and the average daily weight gain of the nursing piglet from 7 to 28 days of age is significantly increased by 13.2%, and the average daily feed intake is increased by 12.1%. The piglet morbidity rate and piglet diarrhea index were reduced.

Wang et al. 5 found that adding stevia or Rebaudioside A to the diet of “Duroc × Landrace × Large” weaned piglets can significantly increase the daily feed intake and average daily weight gain of piglets, reduce the feed conversion ratio, and significantly reduce the diarrhea rate of piglets. The optimal amount of stevia added is 200-250 mg/kg, and the   The optimal addition amount is 191~213 mg/kg. Liu et al. 52 found that when 200 mg/kg stevia residue extract was added to the diet of weaned piglets, the diarrhea rate of weaned piglets was significantly reduced by 55.2%; when the addition amount was 400 mg/kg, the relative abundance of beneficial bacteria in the piglet's intestine was significantly increased. Siriwathananukul et al. 53 added 0.4% stevia to the diet of weaned piglets and found that the daily feed intake of piglets increased significantly by 108.4%, and the average daily weight gain increased significantly by 21.0%.

Yu et al. 54 found that adding 30% stevia residue to the gestation diet of Danbred Landrace sows can improve the intestinal flora structure of pregnant sows, significantly increase the relative abundance of Firmicutes, Actinobacteria, Streptococcus and Verrucomicrobia in the feces of pregnant sows, and reduce the relative abundance of Spirochaetes and Bacteroidetes, thereby improving the body condition of pregnant sows and reducing production costs by 12.5%. and Actinobacteria phyla, and increased the relative abundance of Firmicutes and Verrucomicrobia phyla, thereby improving the body condition of pregnant sows and reducing production costs by 12.5%. Yu Miao 55 added 20%, 30%, and 40% stevia residue to the diets of pregnant sows, respectively, and analyzed the body condition and reproductive performance of sows after giving birth. The results showed that the average feed intake of sows in the lactation period after giving birth in the three test groups was significantly increased by 6.6%, 7.1%, and 5.3%, respectively, and the number of weak piglets piglets were significantly reduced by 1.37, 1.14, and 0.75 heads; and when the stevia residue was added at 30% and 40%, the total milk production of nursing sows was significantly increased by 9.8%, and the length of farrowing was significantly reduced by 0.8 and 0.71 h, thereby improving the reproductive performance of pregnant sows.

Kong Zhiwei et al. 150 found that feeding 5-month-old Bagen pigs with a mixture of stevia residue and basal diet at a ratio of 78:22 for 4 days increased the protein content of the Bagen pork eye muscle by 7.8%, the fat increased by 16.7%, muscle water content decreased by 2.7%, total amino acid content and flavor amino acid content increased by 7.7% and 6.2% respectively, promoting the deposition of amino acids and polyunsaturated fatty acids in the muscle and improving pork flavor and meat quality. In addition, adding 0.2% stevia to the diet of fattening pigs can significantly increase the average daily weight gain of fattening pigs by 57. Xiong et al. 58 found that adding stevia residue extract to the diet can effectively improve the production performance and antioxidant capacity of growing and fattening pigs.

3.2 Stevia in poultry production

In addition to the pig industry, stevia and its industrial by-products have also been partially applied in poultry production. Kong Zhiwei et al.5 showed that replacing 10% of the basic diet of Muscovy ducks with fermented stevia residue can increase the protein and moisture content of the breast muscle by 2.2% and 1.5%, respectively, and significantly reduce the ash content by 5.8%. It also increases the content of amino acids and unsaturated fatty acids in the duck muscle by 1.5% and 5.3%, respectively, thereby improving the muscle quality of Muscovy ducks. Zhu Chunliu 35 added 2.0 and 4.0 g/L stevia chlorogenic acid to the drinking water of egg-laying hens, respectively.

It was found that the number of bacteria in the cecum of laying hens was significantly reduced, and the number of lactobacilli, lactobacilli and bifidobacteria was significantly increased. The effect was directly proportional to the addition level, indicating that stevia chlorogenic acid has the effect of improving the intestinal flora environment of laying hens.

Adding stevia chlorogenic acid to the drinking water of egg chicks infected with Escherichia coli O₇ can significantly reduce the mortality rate of chicks infected with Escherichia coli, significantly reduce the expression level of pro-inflammatory factors in the ileum of chicks, increase the relative abundance of the Firmicutes phylum in the cecum of chicks, and reduce the relative abundance of the Bacteroidetes and the relative abundance of the Proteobacteria phylum, indicating that stevia chlorogenic acid has the effect of improving intestinal barrier damage caused by E. coli infection, improving the immune capacity of the chick body and improving the intestinal flora environment. 60 Zhu Yuan et al. 1 found that feeding chicks with a product of 1.0 mg/mL stevia chlorogenic acid and Lactobacillus brevis fermented for 8 h can effectively reduce the number of E. coli in the cecum of chicks, increase the abundance of beneficial bacteria such as lactobacilli, lactobacillus and bifidobacteria, inhibit the proliferation of E. coli, and thus reduce the mortality rate of chicks infected with E. coli.

Wu Lifei et al. 2 found that by constructing a model of oviductitis in laying hens, adding 200 mg/kg stevioside isochlorogenic acid to the laying hen diet can significantly reduce the mortality rate and unqualified egg rate of laying hens during the laying period caused by oviductitis by 95.9% and 71.6%, respectively, and increase the laying rate by 57.4%. Adding 200 mg/kg stevioside isochlorogenic acid to the diet of healthy laying hens in the late production period significantly increased the laying rate by 4.7%, the egg shell thickness by 24.8%, the rate of sand-shelled eggs by 42.4%, and the rate of broken eggs by 80.2%, indicating that stevioside isochlorogenic acid can significantly improve the production performance of laying hens in the late production period and improve egg quality. 63

Tao Zhihua et al. 64 found that feeding 4-day-old chicks with clysterized pepsin and adding 2000 mg/kg stevia extract to the diet can improve the degree of clysterization in chicks and improve the slow growth rate and mortality caused by clysterization. Studies have found that adding 0.3% stevia extract to the diet of green-footed broilers significantly increased the daily weight gain of chicks by 20.2%, improved feed utilization, significantly increased serum albumin levels by 2.5%, and significantly increased plasma free fatty acid content increased significantly by 1.6%, and the bursa of Fabricius index, spleen index, and thymus index of the immune organs of the chicks increased by 47.4%, 10.5%, and 34.7%, respectively, enhancing the immune capacity of the chicks by 65-66].

 Zhong Min et al. 67 found that adding 0.1%, 0.3%, and 0.5% stevia residue to the diet of 28-day-old Ningdu yellow chickens significantly increased the body weight of Ningdu yellow chickens at 119 days of age by 1.9%, 2.5%, and 1.7%, respectively, and significantly increased the average daily weight gain  2.6%, 3.4%, 2.4%, and the feed conversion ratio was significantly reduced by 1.6%, 2.5%, and 1.6%. When the Stevia rebaudiana residue was added at a rate of 0.3% or 0.5%, the Ningdu yellow chicken's slaughter rate was significantly increased by 1.6% or 1.1%, the breast muscle rate was significantly increased by 7.6% and 0.6%, the leg muscle rate increased significantly by 8.9% and 8.0%, and the addition of 0.1% to 0.5% stevia residue had no significant effect on the feed intake and serum biochemical indicators of Ningdu yellow chickens, but it had the effect of improving the growth performance and meat performance of Ningdu yellow chickens.

Adding steviol extract to the drinking water of commercial broilers can significantly increase the antibody titer of broilers to Newcastle disease vaccine, and has the effect of enhancing humoral immunity. 68 Qiu Guangzhong et al. 6 found that adding 1% stevia extract to the diet of Nic hens can significantly increase the egg production rate by 3.9%, reduce the feed-to-egg ratio, the total number of broken eggs and the mortality rate of hens, and has the effect of improving the production performance of hens.

3.3 Stevia application in ruminant production

There have been few studies on the application of stevia and its by-products in ruminant production. He Li et al. 7 found through in vitro fermentation experiments that compared with the group supplemented with soybean straw, adding 8 g/L stevia residue can significantly reduce the 24-hour methane production in the sheep rumen by 17.6%, and significantly increase the microbial protein and volatile fatty acid content in the rumen fluid by 33.0% and 40.8 %, indicating that stevia residues can increase the metabolic activity of rumen microorganisms, promote the conversion of ammoniacal nitrogen to microbial protein, and enhance the fermentation of carbohydrates in the rumen. Han et al. added 400 and 800 mg/kg stevia to the feed of black goats, and found that the goats' feed intake increased by 2.8% and 4.2%, respectively. The apparent digestibility of neutral detergent fiber (13.1% and 9.6%) and acid detergent fiber (12.1% and 9.8%) in the rumen of goats was significantly improved, indicating that stevia has the effect of promoting the digestion of feed by goats.

Jiang et al. 72 used stevia hay to replace 6% alfalfa hay with the same nitrogen and energy content in the basal diet of Holstein cows. They found that the use of stevia hay to replace alfalfa hay did not affect the feed intake of Holstein cows, but it increased milk yield and milk fat content increased by 5.0% and 2.6% respectively, and the digestibility of neutral detergent fiber and acid detergent fiber in the diet increased by 6.1% and 9.9% respectively, which improved the nitrogen utilization rate by 50.5%, thereby improving the lactation performance of lactating cows and their ability to digest the diet.

Jiang Maocheng [73] found that adding 3.5% and 7.5% stevia granules to the diet of Holstein cows significantly increased the dry matter intake of cows by 4.9% and 4.8%, respectively, but had no significant effect on the milk composition, ruminal fermentation, and serum biochemical indicators of lactating cows. The results show that adding a certain amount of stevia granules does not affect the production performance and physiological functions of dairy cows, and it has the potential to be developed into an unconventional feed. Li Peng et al. [74 added 1, 2, and 4 g/head of stevia extract to the diet of Angus calves, respectively. The results showed that as the amount of stevia extract added increased, the diarrhea rate of calves decreased by 25.6%, 57.1%, and 66.7%, respectively; when the amount added was 2 or 4 g/head, head, the average daily weight gain of weaned calves was significantly increased by 4.2% and 5.1% respectively; when the amount of stevia extract added to the diet was 4g/head, the important growth performance indicators such as body height, body slant length and chest circumference of calves were significantly improved, indicating that stevia extract has the effect.

4 Conclusion

Stevia is rich in active substances and has significant effects in terms of antioxidant stress, promoting intestinal health and boosting the immune system, and has the potential to be used as a functional feed resource. However, the application of stevia in animal husbandry is relatively rare, and in particular, the application effect and mechanism of action of stevia residue, its industrial by-product, requires systematic and in-depth research.

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