Dr. RAJESH KUMAR SINGH, (LIVESTOCK & POULTRY CONSULTANT), JAMSHEDPUR, JHARKHAND,INDIA
Recent ban on the use of antibiotic growth promoters (AGP) in poultry feeds has drawn the concerns of researchers towards the presence of various natural substances like medicinal herbs, as a new class of additives to animal and poultry feeds, have beneficial properties such as anti-oxidant, anti-microbial and anti-fungal as well as immune-modulatory and anticoccidial effects. There are plenty resources of different kinds of medicinal herbs which can be used as natural feed additives for poultry. Commonly known herbs that have received particular attention from researchers are Aloe vera, Fenugreek, Ashwagandha, Moringa oleifera, Cinnamon, Tulsi, Garlic, Pepper etc. Herbal preparations help in the digestion process and being a component of nature, these preparations are considered safe, cost effective and environment friendly with no side effect. Hence, their inclusion in the diet should be encouraged to enhance the bird’s performance, improve feed utilization, maintain health and alleviate adverse effect of environmental stress.
So far, subtherapeutic dosage of antibiotics has been used more than 50 years in poultry nutrition to promote growth performance and prevent diseases . However, continuous use of in-feed antibiotics is suspected to result in common problems such as increasing resistance of pathogens to antibiotics , accumulation of antibiotic residues in animal products and the environment , and imbalance of normal microflora . Thus, efforts have been made to substitute antibiotic growth promoters (AGPs) with possible alternative growth promoters. Phytogenic and herbal products have received increased attention as natural additives in recent years because they have been accepted by consumers as natural additives .
Aloe vera (AV) (Aloe barbadensis Miller) is a well-known medicinal herb and it has been used for commercial and therapeutic properties in many parts of the world . AV gel contains compounds with proven antibacterial, antiviral, antifungal, antioxidant, anti-inflammatory, anti-diabetic, immunomodulatory, and wound healing properties . AV gel contains acemannan, which has been identified as the primary polysaccharide . Polysaccharides can affect the humoral immune response and cellular immunity . Studies showed that acemannan is able to activate of macrophages to release inflammatory cytokines such as interleukin-1 (IL-1), IL-6, and tumor necrosis factor-α (TNF-α) . AV gel has demonstrated antimicrobial properties against a wide range of pathogenic bacteria such as Staphylococcus aureus and Escherichia coli .
Darabighane and Nahashon observed the beneficial influence of AV gel on intestinal microflora and immunity in broiler chickens. Furthermore, Feng et al. reported positive effects of AV relative weight of lymphoid organs of broilers. Despite these findings, few studies have evaluated efficiency of AV on performance, intestinal microflora, and immune responses in broilers. There is a possibility of supplementing broiler drinking water with 1% AV gel as an alternative for AGP substitution.
Aloe vera is not only a natural healer, it’s also a growth enhancer in poultry. Hearing that, one might think, it’s too good to be true. Essentially, the leaves of Aloe vera are often for external uses only, they are not meant to be taken in. But with the study of Bejar and Colapo, it’s became clear that it’s safe for animal intake. Thus, it is important to know what’s in the Aloe vera that makes it both a natural healer and a growth promoter in chickens.
Physically, the leaf of an Aloe vera is composed of three layers. The first layer contains a clear gel, which is contained within the cells of the generous inner portion. Then there’s the anthraquinones contained in the bitter yellow sap of the middle leaf layer and the fibrous outer part of the leaf that serves a protective function.
The content of the aloe vera leaf is just 0.5 – 1.5 percent solid, with an average pH value of 4.55. This solid material contains over 75 different nutrients including vitamins and minerals. Aloe vera is rich in vitamins and minerals. Specific vitamins include: Vitamin A (Beta-Carotene), Vitamin B1 (Thiamine), Vitamin B2 (Riboflavin), Vitamin B3 (Niacin), Vitamin B5, Vitamin B6 (Pyridoxine), Vitamin B12, Vitamin C, Vitamin E, Choline, and Folic Acid. The vitamins A, C, and E are responsible for the aloe’s antioxidant activity while vitamin B and choline are involved in amino acid metabolism and vitamin B12 is required for the production and development of blood cells. Among the important minerals found in Aloe vera are calcium, chromium, copper, iron, magnesium, manganese, potassium, phosphorous, sodium, and zinc. These minerals are essential for good health and are known to work in synergistic combinations with each other, with vitamins and other trace elements.
Aside from vitamins and minerals, Aloe vera is rich with enzymes (help the breakdown of food sugars and fats), hormones (assist in healing and antiinflammatory activities), sugars (i.e. glucose and fructose that provide anti-inflammatory activity), anthraquinones or phenolic compounds (aid in absorption from gastro-intestinal tract and have anti-microbial and pain killing effects), lignin (increases blood circulation), saponins (provides cleansing and antiseptic activity), sterols (antiseptic and analgesic), amino acids (basic building blocks of proteins in the production of muscle tissue), and salicylic acid (work as a pain killer).
With the build-up nutrients and capability of Aloe vera both as natural healer for humans and growth promoter in poultry, it’s not surprising that the scientific community finds interesting and effective uses of this wonder plant.
Effect on growth performance:
Greater body weight and better feed conversion ratio (FCR) are among important economic goals in broiler farming. The bans on application of AGP have affected this goal, resulting in poor growth performance of broilers. Many studies have examined potential effects of feed additives, like prebiotics, probiotics, organic acids, and herbs, on growth performance compared to those of antibiotics.
Aloe vera, as an additive to broiler chicken feed, has great potentials for improving growth performance, carcass characteristics, haemato-biochemical parameters, intestinal health, immune system response and cost of production. It can also be used in controlling coccidiosis. Advantages of Aloe vera added to broiler feeds depend on several factors: form of use (powder, gel, extract (ethanolic or aqueous), polysaccharide extracted from gel), dosage, genetics of broilers, ingredients of diet, and farm management. Therefore, more studies are required to determine effective dosage and form of use.
The most important part of Aloe vera is its leaf. › Alo vera leaves is composed of two main sections: 1. Latex 2. Gel › The gel contained in Aloe vera leaves is composed of:
1. About 98.5% to 99.5% water.
2. The remaining dry matter contains more than 75 biologically active ingredients which have medicinal effects that are useful in treating diseases.
Major ingredients of Aloe vera include;
5. Low-molecular-weight compounds
These compounds give Aloe vera its effects as;
Saccharides › Almost 60% of dry matter of Aloe vera gel is composed of polysaccharides. › Numerous studies suggest that many benefits of Aloe vera are attributable to polysaccharides contained in Aloe vera gel.
A compound often analyzed by researchers is the polysaccharide acemannan which has:
3. Anti-tumor effects
Effects on Intestinal Microflora :
Balance of intestinal microflora in broilers is an important factor contributing to improved growth performance and immune response. › Anti-bacterial compounds, like herbs, play a significant role in balancing and improving intestinal microflora in chickens. Aloe Vera Gel Shows an Antibacterial Action › Aloe vera has an impact on intestinal microflora in broilers; – Increase in Aloe vera gel in broiler feeds (1.5%, 2%, and 2.5%) leads to increased Lactobacillus count and decreased E. coli count. › When acemannan (0.1% and 0.05%), polysaccharide (0.1%), and Aloe vera gel (0.1%) were added to broiler feed, they; 1. Increase lactobacillus count 2. Reduce bifidobacteria count as well as a reduction in E. Coli count.
Mechanism of Action :
Unknown › It is likely to be similar to the anti-bacterial effects of some herbs and mushrooms that improve intestinal microflora. › It is also likely that the polysaccharide contained in Aloe vera (acemannan) follows a mechanism like that of prebiotics since studies found prebiotic-like impacts of polysaccharides contained in medicinal herbs and mushrooms. › Other researchers attribute anti-bacterial effects of Aloe vera to its fumaric acid content.
Effects on Immune Response :
Previous studies show that polysaccharides contained in medicinal herbs and mushrooms can improve the response of immune system. › An important property of Aloe vera that has been the subject of many in vivo and in vitro experiments is improvement in immune response, probably due to the acemannan contained in Aloe vera.
Mechanism of Action :
Acemannan contained in Aloe vera gel is a β (1-4)-linked acetylated mannan containing mannose; 1. Mannose can attach to mannose receptors in macrophages and activate these macrophages. 2. Acemannan can stimulate production of cytokines.
Aloe Vera and NDV :
Darabighane et al. (2012) shown that › An increase in antibody titer against Newcastle disease virus (NDV) on days 24 and 38 by adding Aloe vera gel to broiler feeds (at 1.5%, 2%, and 2.5%). Valle-Paraso et al. (2005) › Broilers treated with 2% Aloe vera gel (mixed with their drinking water) showed significant increase in antibody titer against NDV on days 37 and 52, compared to the control group.
Alemi et al. (2012) › An increase in antibody titer against NDV after adding Aloe vera gel powder (at 0.5%, 0.75%, and 1%) to broiler feeds. Jiang et al. 2005 › An improvement in antibody titer in broilers against NDV as a result of adding acemannan (0.1% and 0.05%), polysaccharide (0.1%), and Aloe vera gel (0.1%) to broiler feed.
Aloe Vera and WBCs :
Assessment of blood parameters showed an increase in total white blood cell and lymphocyte counts on days 37 and 52 for broilers that received 2% Aloe vera gel (mixed with drinking water) compared to the control group.
Effects on Growth Performance :
In an experiment comparing the effects of Aloe vera gel (mixed with feed) and AGP (virginiamycin): 1. AGP resulted in better growth performance compared to the performance of groups that received Aloe vera gel (at 1.5%, 2%, and 2.5%), and the control group. 2. No significant difference was observed between the antibiotic group and the 2% Aloe vera gel group in terms of body weight gain and FCR.
Effects on Coccidiosis :
Yim et al. (2011) shown that Broilers received Aloe vera powder (0.1%, 0.3%, and 0.5%) had smaller fecal oocyst shedding count compared to infected group fed with the standard diet.
In last decade, there is a renewed interest in the development of herbal drugs which has underlined understanding the mechanism of action rather than blind faith in people and stories, as in the past. Several approaches in exploiting the herbal wealth of the world in phytomedicine have explored many phytochemicals from variety of plants. Nonetheless, even with the limited reports on mechanism of activity it has become obvious that numerous mechanisms would have been involved in different activities of a given herbal medicine. It could be concluded that, under the condition of the present study, Aloe Vera powder at 0.3% dietary inclusion are more efficient than control group on improving broiler performance. Therefore, dietary inclusion of Aloe Vera in broiler diets is highly recommended, it will be interesting to try different inclusion levels of Aloe Vera since there is no detrimental effect recorded both health wise and performance.