The productive performance of laying hens improved significantly when adding aqueous extract of aloe vera leaf gel at a concentration of 2 ml/kg body weight [8].

This study aims to demonstrate the importance of aloe vera leaves in poultry birds.

DESCRIPTIONS OF ALOE VERA

Aloe Vera is a succulent herbaceous plant that tolerates drought and is a perennial tropical plant. It is distinguished by its green leaves (Figure 1), which mature 7-8 months after planting. It has a large base. The leaves are approximately 25-30 cm long and 10 cm wide. The number of its leaves ranges between 12-16 leaves, the sides of which are surrounded by thorns, and at its base there are short stems. The plant is sparsely branched, and the plant lives up to 12 years [9].

The leaves of the Aloe Vera plant consist of three main layers (Figure 2), the first (outer) layer is the thickest, it consists of carbohydrates and proteins. The presence of bundles of transport vessels that transport nutritional elements to different parts of the plant, the second (middle) layer contains latex, which is a yellow-colored substance that gives a bitter taste, the third (inner) layer is a transparent material called gel, in which the percentage of water is about 99% [10].

Its flowers (Figure 3) are large and yellow in color, and are borne on a long stem that grows from the middle of the plant [11].

A Brief History of Aloe Vera

Studies have indicated that the original homeland of the Aloe Vera plant is in the Arabian Peninsula, it was transported by John Goodyew to Europe in 1655 AD, to benefit from its therapeutic properties, it was then transferred to the United States of America in 1800 AD [12]. Aloe Vera has been used since ancient times, it was known through Egyptian sculptures, which were estimated to be more than 6,000 years old. The ancient Egyptians used to grow the aloe vera plant in special terraces and in corridors leading to the tombs of the Pharaohs in the pyramids, at that time, it was called the plant of immortality, as it was considered one of the gifts given at the burial of the Pharaohs [13].

Tanwar [14] showed that there are manuscripts of Egyptian papyrus tablets dating back to 1550 years BC, refers to prescriptions made from aloe vera, it was used as a cosmetic material and was used by the queens of Egypt, especially Cleopatra and Nefertiti. The discovery of Sumerian clay tablets dating back to 1200 BC, medicinal uses in Mesopotamia indicate that when diseases spread, they placed aloe vera leaves on the doors of homes.

Aristotle convinced Alexander the Great, who was his chief advisor, to seize the Arabian Peninsula, especially Socotra Island, which is one of the islands of Yemen. The purpose was to take the aloe vera plant to treat wounded soldiers in the fourteenth century BC [15]. The Greek physician Dioscorides worked on introducing aloe vera leaves into many therapeutic uses in 50 BC. In 300-400 BC, the plant was introduced to the continent of Asia, its residents used aloe vera leaves to treat many diseases, including sinusitis, fever, skin diseases, and seizures in children [16].

The aloe vera plant was widely known throughout Europe as a treatment for many diseases in the fourteenth and sixteenth centuries AD [17]. In 1820, the aloe vera plant was officially used in the United States of America as a disinfectant and skin protectant [18].

Chemical Composition of Aloe Vera Leaves

Aloe vera leaves vary in their chemical composition according to their growing regions and environmental conditions [19-21]. Studies have indicated that the moisture content of aloe vera leaves ranges between 90-97% [22-24]. Waris [25] noted that the crude fat content of dried aloe vera leaves reached 14.86%. Aloe vera leaves are rich in fatty acids, especially essential fatty acids such as linoleic, linolenic and arcadonic. Gohel [26] showed that the raw ash based on the dry weight of aloe vera leaves reached 15.50%. As for protein, the content of air-dried aloe vera leaf powder reached 4.73% [27]. Pandey and Singh [28] indicated that the leaves contain the protein lectin and 20 amino acids out of 22, and that seven of them are essential amino acids (Table 1). The percentage of crude fiber in aloe vera leaves reached 12.33% [29]. The total carbohydrate content of air-dried aloe vera leaves reached 73.08%. Suker [7] indicated when conducting a chemical analysis of aloe vera leaves on the basis of dry weight that the percentage of moisture, bulk matter, crude protein, crude fat, total ash, soluble carbohydrates, crude fiber and assimilated energy, it reached 9.28, 90.72, 6.34, 3.92, 12.54, 59.21, 17.96% and 2421.21 kcal/kg, respectively.

Organic Acids in Aloe Vera Leaves

Añibarro-Ortega [23] showed that aloe vera leaves contain a number of organic acids and tocopherols (Table 2).

Fatty acids in aloe vera leaves

Aloe vera leaves contain saturated and unsaturated fatty acids (Table 3) [23].

Vitamins in Aloe Vera Leaves

Maurya and Singh [31] noted that the content of aloe vera leaves of vitamin A reached 62% per 100 g and of vitamin C reached 50% per 100 gm. Vega-Gálvez [32] indicated that the vitamin E content of aloe vera gel was 0.21 mg/100 gm.

ACTIVE COMPOUNDS IN ALOE VERA LEAVES

Phenolic compounds

Phenolic compounds are a natural product of plant metabolism (Figure 4), it is a natural pigment responsible for color, found in all parts of the plant, and it means yellow in Latin, derived from the word flavus. It was discovered by researcher Albert in the nineteenth century of the last century [33]. It is characterized by its ability to dissolve in organic solvents. They are similar to tannins but simpler in structure [34]. It has a major role as an antioxidant, anti-inflammatory and antispasmodic [35]. It is also anti-cancer and anti-hypertension, in addition to its role in stimulating immunity and dilating blood vessels, as well as anti-fungal and anti-viral [36]. Ibe et al. [37] found that the percentage of phenols in aloe vera leaves reached 1.43 mg/g, in the form of glycosides, specifically the compound aloin.

Glycosides

It is found in plants in general. It has a solid consistency and plays a major role in protecting plants from insects and agricultural pests. It dissolves in water and decomposes into a sugar part called Glycon and a non-sugary part Aglycon (Figure 5). It has a bitter taste [34]. Glycosides are used in the medical field. They have been used to treat heart diseases, Cardio Tonic, a laxative, and are used as a pain reliever as well as a local anesthetic. It prevents capillary rupture, stops bleeding, treats urinary tract infections, and also breaks up stones [39].

Anthraquinones

Anthroquines are cyclic aromatic organic compounds that belong to the ketone family (Figure 6). It consists of an anthracene ring with a keto group. It is found in plants either in free form or bound to a glycoside form, and is yellow or light gray to greenish gray in color [40]. Fouillaud [41] indicated that there are more than 700 anthroquine pigments from plant or insect sources. Surjushe [42] stated that anthroquines are phenolic compounds consisting of approximately 12 types. It comes in several forms, including Aloin, Barbaloin, Iaobarnaloin, Anthranol, Aloethic acid, Anthracene, Easter of cinnamic acid, Emodin, Aloe-emodin, Chrysophanic acid, Ethereal oil and Resistannol [43].

Balasubramanian and Narayanan [44] indicated that the most important anthrokines are Aloin and Emodin.  Anthroquines are considered laxatives that are anti-bacterial and anti-viral. It is found in high concentrations in the stem sap and its concentrations decrease in the outer layer of the leaves [45]. The bitter taste in aloe vera leaves, especially in the gel, is due to the effect of anthrokines, especially Barbaloin and Isobarbalon [46]. These two compounds are hydrolyzed in the large intestine and then form active receptors for them. These compounds may act as antioxidants that prevent the formation of free radicals [47]. Mckeown [48] showed that it has effects, including as a laxative, helping in the absorption process within the gastrointestinal tract and reducing hyperpigmentation in cells, especially melanin pigment.

Aloin

The aloin compound is one of the main active anthrogenic compounds (Figures 7-9) found in aloe vera leaves, also known as Barbaloin, it is a yellow-brown compound with a bitter taste. It is a C-glycoside derived from anthraquinone. Its percentage is estimated at about 0.10-6.60% of the weight of the dry leaf [50]. Its molecular formula is C₂₁H₂₂O₉ and its molecular weight is 418.40 g/mol, the aloe vera plant is the main source of this compound [51]. Lee [52] indicated that aloin compound is soluble in some organic solvents, such as pyridine, glacial acetic acid, formic acid, acetone, methyl acetate and ethyl alcohol. The aloin compound is present to a large extent in young leaves and its percentage is less in large leaves, its presence in the roots of the Aloe Vera plant at a concentration of 3.90 micrograms/gm, indicated that 18-60% of the secretions of aloe vera leaves, based on dry weight, are the aloin compound. The circumferential layer of leaves contains yellow leaf secretions called Aloe sap, this substance is secreted directly when the Aloe Vera leaves are cut, and comes out from under the outer layer of the leaves. It is dried and made into tablets to be used as a final product (Figure 5) [53]. It is considered a treatment against many diseases, the most important of which are asthma, diabetes, hemorrhoids, ulcers and arthritis [54].

Tannins

Tannins are phenolic compounds (Figure 10) that are largely present in plants. They are soluble in water and do not dissolve in organic solvents [56]. Its importance is protecting the plant from insects and fungi, and it is also considered a source of energy that the plant benefits from [57]. Lawrence [58] stated that tannins have other names, they are called tannins or astringents, and they have industrial importance through their use in leather tanning. In addition to its medical importance, it is used to treat wounds, burns, and diarrhea (due to its astringent effect). Tannins have an antiviral and antibacterial role, as well as anticancer, and have a high effectiveness in inhibiting the replication of the immunodeficiency virus (HIV) [36]. The percentage of tannins is 4.6 mg/g in Aloe Vera leaves [37].

Flavonoids

Flavonoids are organic phenolic compounds (Figure 11) consisting of 15 carbon atoms linked to two phenyl rings [60]. It is responsible for the colors in plants, especially fruits and flowers, which acts as an attraction for insects and birds [61]. In addition to its inclusion in the composition of many plants, especially those that have more than one aromatic ring. Tannins are in the form of glycosidic compounds [34]. It has a major role in terms of health, as it protects cholesterol and low-density lipoprotein (LDL) from oxidation inside the body’s cells, by inhibiting the activity of the enzymes Cycloxyginase and Lipoxygenase, which contribute to the oxidative process, it also plays a major role in inhibiting the growth of microorganisms, its presence in aloe vera leaves reached 4.064 mg/g [37].

Saponins

Saponins are organic phenolic compounds (Figure 12) that are present in different proportions in plants. It dissolves in water (because it has the sugar part in its structure), but it does not dissolve in organic solvents. Saponins are characterized by giving the plant a bitter taste [57]. Saad [63] indicated that saponins have a major role in the medical field, as they treat high blood sugar. In addition to its role as an antioxidant, anti-cancer and anti-fungal. Saponins are characterized by the formation of foam in water, therefore, it is used in the field of cleaning and making toothpaste. Aloe vera leaves contain saponins at a rate of 360.85 mg/g [37]. Its gel contains 3% [64].

Medicinal Plants as Natural Antioxidants

 Medicinal plants are natural antioxidants because they contain a number of active compounds, reduce the formation of free radicals, which prevents negative effects on public health compared to medications [66]. Salami [67] showed that the effectiveness of medicinal plants depends on the age of the bird, the appropriate dose, as well as the time period for adding them. Akintayo-Balogun and Alagbe [68] indicated that medicinal plants contain many active compounds, including flavonoids, quines, sulfites, polyphenolics, carotenoids, saponins, alkaloids, tannins and phenols, gives the plant the ability to perform its functions as an antioxidant. Abdel-Moneim [69] showed that active compounds in medicinal plants, especially phenolic compounds, have a major role in suppressing free radicals by binding iron or copper ions, as well as giving the hydrogen atom or transferring electrons. Vivek and Sharma [70] explained that medicinal plants have the ability to inhibit the activity of free radicals, preventing the decomposition of hydrogen peroxide into water and oxygen, by acting as a donor to the hydrogen atom for the purpose of breaking the fat oxidation reaction.

Aloe Vera Leaves as An Antioxidant

Aloe vera leaves are considered a natural antioxidant as they contain many active compounds [71], these active compounds have high effectiveness as antioxidants, which work to curb or prevent the formation of free radicals that cause significant damage to cells [72]. Dosing the alcoholic extract of aloe vera gel to diabetic mice at a concentration of 300 ml/L of body weight at the age of 30 days, led to an increase in the activity of antioxidants Glutathione Peroxidase (GSH-PX) and Superoxide Dismutases (SOD) compared to the control treatment [73]. Yadav et al. [74] indicated that adding aloe vera leaf powder at a level of 0.5 and aloe gel powder at a level of 2% to feed and 2% of fresh aloe vera gel to drinking water, led to an increase in the levels of (GSH-PX) and (SOD) enzymes in the blood plasma of broiler chickens when compared with control.

Medicinal Properties of Aloe Vera Leaves

Aloe vera leaves and their oils have been used since ancient times to treat many diseases, especially skin diseases.  The active compounds found in aloe vera gel help in healing wounds, as a result of the presence of amino acids that work to restore the structure of injured tissues [54]. Tarameshloo [75] indicated that aloe vera leaves prevent the formation of a small scar on the skin as a result of wound healing. Mansour [76] noted that aloe vera leaves work to protect the stomach from ulcers, in addition to its treatment, it contains anti-inflammatory compounds, which work to increase both mucus and stomach contraction.

Aloe vera leaves can treat skin ulcers, dandruff, skin burns, dry skin, ulcers resulting from colds, and mouth ulcers. Aloe vera leaf gel has an anti-inflammatory effect due to the presence of active compounds, the most important of which are anthroquinone and carmon. It was found that taking the gel at a rate of 2% led to a reduction in the severity of the disease. Pain and also reduced wound size in patients with aphthous stomatitis [77].

Aloe vera has an effective effect in reducing and treating joint inflammation. It also has anti-bradykinin activity, it contains the enzyme bradykinase, which reduces inflammation [78]. Aloe vera also has high effectiveness in treating cancer because it contains a large group of active compounds, especially glycoproteins and polysaccharides, which have high effectiveness in treating different types of cancer [64]. It was found that effective compounds extracted from aloe vera, especially Barbaloin, aloe-emodin and aloesin, treat cancer cells [79].

Hamman [80] indicated that aloe vera has high activity in treating type 2 diabetes, as well as in treating constipation as a result of aloe vera containing active laxative compounds. Mulay [81] found that taking 0.25 milligrams of aloe vera within 6-12 hours leads to increased bowel movement and thus gets rid of constipation. Syed [82] stated that aloe vera has high activity against herpes, as 0.5% of aloe vera extract can treat the disease by accelerating wound healing, as well as preventing or reducing cracks and accelerating healing. Capasso [83] explained that aloe vera extract prepared for 3-10 days led to the elimination of chronic bronchial asthma as a result of it containing active compounds (Prostanoids).

Aloe vera is effective in treating toothache and gum ulcers, as well as in treating gingivitis and stopping bleeding [84]. Kapoor [85] indicated that aloe vera leaves are considered a nutritional supplement because they are included in many food products, for example juices, ice cream and sweets. Radha and Laxmipriya [77] stated that aloe vera leaves have an antioxidant effect that occurs in the body’s cells, due to it containing active compounds, they are carotenoids, α-tocopherol, vitamins E and C, cornic acid, flavonoids, saponins, tannins, flavonoids and carotenoids.

Aloe vera has an effective effect in reducing cholesterol and triglycerides in the blood. Kumar et al. [5] showed that aloe vera gel has the ability to lower cholesterol levels and thus reduce the risk of heart disease and blood vessel blockage. Iwu [86] indicated that aloe vera gel is used in the manufacture of cosmetics without any side effects on the skin, in addition to its use in the manufacture of soap, shampoo, and creams.

Aloe Vera has a high ability to inhibit and prevent the growth of microorganisms such as bacteria, fungi, and viruses, which cause diseases, as well as prevent the growth of organisms that cause food rot [6]. Misir [87] stated that aloe vera gel is the best coating for covering food materials, increasing the life of the food item and preventing it from spoiling, as a result of aloe vera gel containing polysaccharides, which are a natural barrier to moisture and oxygen that cause food spoilage.

The Effect of Aloe Vera Leaves on Some Productive Traits of Broiler Chickens

The use of aloe vera leaves, whether directly or in the form of powder or extract, has a positive effect on the productive performance of poultry birds. Odo [88] showed that adding aloe vera gel powder at a concentration of 0.25 gm/kg to the feed from the age of one day until the marketing age (35 days) significantly improved the performance of broilers. Mmereole [89] indicated that adding aloe vera leaf powder to the diet at a rate of 1% led to an increase in weight and feed conversion factor compared to the control, in addition to a significant improvement in the productive performance of broilers when added to drinking water at a concentration of 1.5 from one day of age up to 42 days of age of broilers.

Darabighane [90] explained that giving aloe vera gel led to weight gain, improved feed conversion efficiency, and increased feed consumption compared to control. Edeh [91] indicated that using aloe vera gel extract at a concentration of 1.2 ml/liter of drinking water led to a significant increase in the average body weight of broilers compared to levels of 0, 0.4, and 0.8 ml/liter of drinking water. Adding aloe vera leaf powder at levels of 1.0, 2.0, 5.0 and 10.0% to feed has a positive effect on both the feed conversion factor and feed consumption [92]. Shokraneh [93] noted that adding aqueous extract of aloe vera gel to drinking water led to a significant improvement in body weight and feed conversion efficiency. Adding the aqueous extract of aloe vera leaf powder at concentrations of 5.0, 10.0, and 15.0 ml/liter of drinking water to broilers improved the performance of broilers, represented by body weight, feed consumption, water consumption, and feed conversion factor [94].

Yadav [74] indicated that adding aloe vera leaf powder and gel to the feed at a ratio of 0.5% of aloe vera powder and 0.2% of aloe gel significantly improved the average body weight and carcass weight. Singh [95] observed that using aloe vera leaf powder at a concentration of 0.1, 0.3 and 0.02% to the broiler diet at the age of 1-42 days improved the performance of broilers, using 50 mg/L of aloe vera leaf extract to drinking water led to an improvement in the feed conversion factor for 42-day-old broilers, adding a mixture of medicinal plants, including mint leaf powder and aloe vera gel, at a concentration of 10 gm/kg feed, it significantly improved both body weight and weight gain compared to the two treatments with the antibiotic Virginiamycin at a concentration of 10 ppm and the control treatment [96]. The alcoholic extract of aloe vera leaves in the drinking water of broilers at a level of 50 mg/liter of drinking water led to a significant increase in both body weight and weight gain compared to the control treatment. The use of aqueous extract of aloe vera gel at a concentration of 10 ml/liter of drinking water significantly improved the performance of broilers exposed to infection with the Coccidiosis parasite at the age of 21 days compared to concentrations of 5 and 15 ml/liter of drinking water, in addition to the control treatment [97].

A significant increase in the weight of broilers when a water extract of aloe vera gel was added to the drinking water at a concentration of 50 ml/liter of drinking water at different pH levels (3, 7 and 12), compared to two treatments adding the antibiotic Enramycin at a concentration of 100 mg/kg feed and the control treatment at 35 days of age [98]. The use of aloe vera leaf powder at concentrations of 5, 15 and 30 grams per kg of feed, and the aqueous extract of aloe vera gel at concentrations of 15 and 30 ml/liter of drinking water, it significantly improved both body weight and cumulative weight gain of broilers compared to the control treatments and the antibiotic neomycin at a concentration of 0.5 g/kg feed at 35 days of age [7]. Arif [99] showed that adding 0.25% of aloe vera leaf powder and 0.25% of clove powder to the diet led to a significant increase in both body weight and an improvement in the feed conversion factor compared to the rest of the treatments.

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  Table 1
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  Table 2
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  Table 3