What Is the Use of Ginger Extract in Animal Feeding?

Ginger is the fresh root of the perennial herb of the genus Zingiber. It can be used as a medicinal plant and is widely used in the treatment of diseases [1-2]. Ginger extract (GE) is a plant extract obtained from ginger. It has antioxidant [3], anti-inflammatory [4], lipid metabolism regulation [5], immunomodulatory [6], anticancer [7] and antibacterial [8] physiological functions. With the shortage of feed resources, the indiscriminate use of antibiotics and food safety problems becoming increasingly serious, it is urgent to find new plant-derived feed that is safe to use and effective. Ginger extract is a good choice for a green and safe feed additive because it is natural and harmless and has multiple physiological functions. This article reviews the main active ingredients, physiological functions and applications of ginger extract in livestock and poultry production, providing a theoretical basis for its further development and utilization.

1 Main active ingredients of ginger extract

Ginger extract is a mixture containing a variety of active ingredients, the content of which varies depending on the origin, species and freshness. The complex composition of ginger extract has led to the isolation and identification of more than 400 chemical components [4], including volatile oil, gingerol, diphenylheptanes, etc. [9], as shown in Table 1.

2 Physiological functions of ginger extract

2.1 Antioxidant effect

Many studies have shown that ginger extract has strong antioxidant properties [26-27], which is closely related to its structure. The components of gingerol and diphenylheptane have strong antioxidant properties because they both contain phenolic groups and hydroxyl groups, which are excellent hydrogen electron donor functional groups. When they encounter oxidizing substrates such as reactive oxygen species (ROS), they can easily lose hydrogen ions and bind to them, reducing oxidative damage to the body. At the same time, the new phenolic free radicals formed do not have suitable sites for oxygen attack, so they are chemically very stable and will not become new free radicals to participate in oxidation reactions. Sueishi et al. [28] used a variety of free radical scavenging methods to determine the scavenging ability of ginger against five types of ROS (hydroxyl radicals, superoxides, alkyl radicals, peroxyl radicals and singlet oxygen), It was found that ginger is good at scavenging hydroxyl radicals and singlet oxygen; it was also found that after ginger was heated at 80 °C for 2 h, its scavenging ability for peroxyl radicals and singlet oxygen decreased by nearly 50%. On the contrary, the scavenging ability of superoxide was increased by about 56% after heat treatment. The above results show that the antioxidant activity of ginger under high temperature treatment depends on the type of ROS.

Ginger extract can also activate the antioxidant system by increasing the gene expression and enzyme activity of antioxidant enzymes. ROS is metabolized in the body, which can cause lipid peroxidation in the body, produce malondialdehyde (MDA), damage cell structure, and cause damage to the body. Antioxidant systems exist in animal bodies, and when stimulated by free radicals, the antioxidant systems will automatically remove them to maintain homeostasis. Hosseinzadeh et al. [29] treated chondrocytes with ginger extract at two different concentrations of 5 and 25 μg/mL for 24 h, then incubated with 10 ng/mL interleukin-1β (interleukin-1β, IL-1β) for 24 h to observe the effect of ginger extract on IL-1β-induced intracellular ROS production and lipid peroxidation. The results showed that ginger extract can reduce IL-1β-induced ROS and MDA production in C28I2 cells, and increase the expression of antioxidant enzyme genes, including superoxide dismutase (SOD), glutathione peroxidase (glutathione peroxidase, GSH-Px) and catalase (CAT) mRNA expression. Mohamed et al. [3] studied the ameliorative effect of ginger extract on lead acetate-induced oxidative hepatotoxicity in mice. and found that ginger extract can very effectively improve the toxic effects of lead, increase the activities of GSH-Px and CAT and the content of glutathione (glutathione, GSH), and reduce lipid peroxidation and the content of MDA in the liver. The above in vitro and in vivo experiments have all demonstrated that ginger extract can increase the expression levels of antioxidant enzymes.

In summary, ginger extract exerts its antioxidant effect mainly through two pathways: on the one hand, ginger extract uses its own structure to directly remove excess free radicals in the body; on the other hand, ginger extract can activate the body's antioxidant system, promote the expression of antioxidant enzyme genes and proteins, and increase the production of antioxidant enzymes (Figure 3). However, the mechanism of its antioxidant function and the specific components involved require further research.

2.2 Anti-inflammatory effect

Ginger extract can inhibit the production of inflammatory mediators by inhibiting the activity of enzymes that produce inflammatory mediators, thereby suppressing inflammatory reactions [30-31]. Prostaglandins (PGs) and leukotrienes (LTs) are inflammatory mediators produced during the body's inflammatory response. They are produced by cyclooxygenase (COX) and 5-lipoxygenase (5-LOX), respectively, through the metabolism of arachidonic acid (ARA). 5- LOX) catalyze the metabolism of arachidonic acid ( ARA) to produce. Ginger extract can inhibit both COX and 5 ⁃ LOX 2 pathways, thereby reducing the production of inflammatory mediators. Flynn et al. [32] found that ginger extract contains a series of compounds with 4-hydroxy-3-ethoxyphenyl (4-hydroxy-3-ethoxyphenyl), such as 6-gingerol, which are dual inhibitors of arachidonic acid metabolism. and they can reduce the production of PG and LTs by human neutrophils to a small extent. Nonsteroidal anti-inflammatory drugs (NSAIDs) NSAIDs can only inhibit PG synthesis and not arachidonic acid production of LTs. When inhibited at one end, arachidonic acid will produce a large amount of LTs through the 5⁃LOX pathway. Compared with NSAIDs, ginger extract has a dual effect and fewer side effects, and it has great potential to become a new class of anti-inflammatory drugs.

Studies have shown that ginger extract can inhibit the expression of inflammatory factors [33]. In inflamed tissues, COX-2 expression is upregulated due to the induction of the COX-2 gene, and its protein level is greatly increased. Ginger extract can not only inhibit COX activity, but also inhibit COX-2 expression at the transcriptional level [4]. The nuclear factor kappa B (NF-κB) signaling pathway is an important signaling pathway for regulating inflammation. Under normal circumstances, NF-κB binds to the inhibitor of NF-κB (IκB). Tumor necrosis factor-alpha (TNF-α) is an important inflammatory mediator that activates the NF-κB pathway. When there is an excess of this type of inflammatory mediator, it will activate the dissociation of NF-κB from IκB, NF-κB enters the nucleus and activates the massive expression of inflammatory mediator genes, exacerbating the inflammatory response.

Phan et al. [33] found that ginger extract can inhibit the mRNA expression levels of TNF-α and IL-1β in synoviocytes activated by TNF-α. Frondoza et al. [34] found that ginger extract can inhibit multiple TNF-α activation pathways. However, further research is needed to determine which component of ginger extract is the active ingredient and the specific mechanism.

In summary, ginger extract exerts anti-inflammatory effects mainly through two pathways: on the one hand, it reduces the production of inflammatory mediators by inhibiting the enzymatic activity of enzymes that produce inflammatory mediators; and reduce the production of inflammatory mediators. On the other hand, it inhibits inflammatory mediators such as TNF-α, which prevents the activation of the NF-κB signaling pathway, thereby reducing the expression of inflammatory factors and suppressing inflammatory responses (Figure 4).

2.3 Lipid-lowering effect

In livestock farming, female animals often become obese during pregnancy, which affects their productivity. Studies have found that ginger extract can regulate lipid metabolism through different mechanisms, such as increasing lipolysis [35], inhibiting fat production [36], and inhibiting intestinal absorption of dietary fat [37].

On the one hand, studies have shown that ginger extract can promote lipolysis in multiple ways. It can not only reduce obesity induced by a high-fat diet by increasing skeletal muscle lipolysis and energy consumption [38], but also by increasing the activity of glycolytic enzymes to promote glucose metabolism and the formation of pyruvate [39], and by activating the sympathetic nervous system and increasing the activity of hormone-sensitive lipase to increase the degradation of adipose tissue [40]. On the other hand, studies have shown that ginger extract can also inhibit lipogenesis. Adipogenesis is the process by which pre-adipocytes become adipocytes, and ginger extract can effectively inhibit the differentiation of pre-adipocytes into adipocytes, thereby preventing fat accumulation [38, 41]. Ginger extract can reduce the gene expression of some enzymes involved in fat production, such as fatty acid synthase (FAS) and acetyl CoA carboxylase (ACC), thereby reducing fat production [42]. Ginger extract has a significant inhibitory effect on carbohydrate-hydrolyzing enzymes such as α-glucosidase and α-amylase [43], which helps reduce the intestinal absorption of carbohydrates and lower blood glucose. In addition, ginger extract can inhibit pancreatic lipase activity and reduce intestinal absorption of dietary fat.

2.4 Immune-enhancing effect

Ginger extract can enhance immunity by promoting the secretion and activity of immune cells. Rahmat et al. [44] found that ginger extract enhances bactericidal activity by inducing lymphocyte proliferation. Xiong et al. [45] showed that ginger can enhance natural killer (NK) cell activity and increase the phagocytic activity and cytotoxicity of peritoneal macrophages in mice. Puri et al. [46] found that ginger feeding increased the macrophage migration index in mice and enhanced humoral immune function. In summary, ginger extract can enhance the activity of lymphocytes and NK cells, activate macrophages and B cells, make them act as major antigen-presenting cells, increase the production of immunoglobulins or regulate the secretion of cytokines [47]. Recent studies have found that ginger extract can also increase lysozyme activity [48], down-regulate nitric oxide concentration [49], and thus enhance the body's bactericidal effect [50].

3 Application of ginger extract in livestock and poultry production

3.1 Application in poultry production

Studies have shown that adding ginger extract to the feed can improve the productivity and immunity of poultry[51-52] (Table 2). Jiang Hui et al. [53] added 10 g/kg ginger powder to the feed and found that the feed intake and feed conversion rate of the local chicken increased. Ademola et al. [54] found that when 20 g/kg ginger powder was added to the feed, the weight gain of broilers in the first 4 weeks increased. The improvement in broiler performance by ginger extract may be related to its intestinal protective effect. Studies have found that 6-gingerol has a protective effect on intestinal ischemia-reperfusion injury in rats [55]. The active ingredients in ginger extract, such as 6-gingerol, can scavenge ROS, increase antioxidant enzyme activity and total antioxidant capacity, reduce the damaging effect of oxidative stress on intestinal structure, and protect intestinal function. Some studies have also shown that ginger extract can relieve diarrhea by inhibiting colonic motility [56].

Abnormal gastrointestinal motility is one of the causes of diarrhea. Ghayur et al. [57] found that ginger extract has an inhibitory effect on potassium-induced guinea pig colon contraction. It can inhibit intestinal motility in rats by inhibiting intestinal nerve excitability and mechanical activity of smooth muscle in vitro [58]. Ginger extract can also relieve immune defense stress in poultry, affect the distribution of the microbial flora, and enhance the intestinal absorption of nutrients, thereby having a better growth-promoting effect [59]. Ginger extract improves feed intake and growth by avoiding damage to the intestinal structure caused by stress and immune damage during production, and by improving the intestinal digestion rate and nutrient absorption rate.

El-mowalid et al.[48] showed that adding 15 g/kg ginger extract to the feed can enhance the immune performance of broiler chickens. Compared with the control group, the immune phagocytosis of the experimental group is enhanced, and the bactericidal activity is enhanced. Ginger extract can increase the number of granulocytes and intermediate cells in the body, thereby enhancing the body's immune function [47]. Granulocytes are one type of immune cell, and intermediate cells are an important part of the body's immune defense, with phagocytic and chemotactic effects. Ginger extract can also activate lymphocytes or enhance the role of cytokines in regulating phagocytes, stimulate the secretion of immunoglobulins [60], and has a significant immunomodulatory effect.

3.2 Application in pig production

Studies have found that adding ginger extract to the feed can improve the immune function of pregnant sows and suckling piglets [61], and can also improve the lean meat rate and meat water holding capacity of growing and finishing pigs [62]. Lee et al. [61] found that after adding 5 g/kg ginger extract to the feed of pregnant sows, the content of immunoglobulin G (IgG) in the sow's colostrum and the mother and pig plasma immunoglobulin G (IgG) content increased significantly; and compared with the birth weight of the ginger extract group and the control group, the birth weight of the ginger extract group was higher than that of the control group.

The above results show that ginger extract can not only increase the IgG content in the body of sows, but also increase the supply of IgG to the mammary glands through the blood circulation, thereby increasing the amount of IgG absorbed by piglets from colostrum and improving the immune function of piglets. Li Xueyan et al. [63] found that adding 10 g/kg ginger to the feed can significantly reduce drip loss of muscle and increase the lean meat rate of Laiwu black pigs. The decrease in drip loss may be related to the antioxidant function of ginger extract, which reduces MDA content by scavenging free radicals in cells, increases the activity of SOD and GSH-Px in cells, reduces the oxidation of fatty acids in cell membranes, and maintains the integrity of membrane structure and function, thereby reducing fluid loss from muscles. The increase in lean meat rate may be due to the fact that ginger extract reduces the absorption of dietary fat and reduces lipid deposition.

3.3 Application in ruminant production

There have been few reports on the application of ginger extract in ruminants, and current research is limited to the effects on nutrient digestion and absorption and serum antioxidant properties. Liu Mingjie et al. [64] added 1.5 g/kg ginger powder to the feed of beef cattle, which significantly improved the digestion of neutral detergent fiber and acid detergent fiber in the rumen of beef cattle, increased the serum GSH-Px activity, reduced the MDA content, and improved the total antioxidant capacity of beef cattle. Rumen microorganisms play an important role in the degradation of crude fiber, and the free amino acids contained in ginger extract may provide nutrients for the rumen flora that decomposes crude fiber[65], resulting in a significant increase in their growth and reproduction, and an increase in the rate of decomposition of neutral detergent fiber and acid detergent fiber. Ginger extract can improve the antioxidant properties of animals because it can remove MDA in the body, increase the activity of antioxidant enzymes, reduce oxidative stress damage in the body, and exert an antioxidant effect [66].

4 Summary

Ginger extract is a natural plant extract that is used for both food and medicine. It is inexpensive and widely available. Combined with its physiological functions, the reasonable use of this resource not only allows the development of new unconventional feed resources, but also provides a solution to the problems of antibiotic substitution and healthy farming faced by the livestock farming industry. There has been little research on ginger extract, and there are still some problems to be solved if it is to be widely used in animal production: 1) The structure and physiological function of individual components are not yet clear, and their mechanism of action needs further research. 2) There is a lack of research on its application in animal production, and further experiments are needed to determine the actual application effect and the optimal dosage.

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