~Sagarika Barman , Pompi R Boro and Dibakar Baruah
Aloe vera (Aloe barbadensis) is a well-known medicinal herb and it has been used for commercial and therapeutic properties in many parts of the world. Aloe vera gel contains compounds with proven antibacterial, antiviral, antifungal, antioxidant, anti-inflammatory, anti-diabetic, immunomodulatory, and wound healing properties (Boudreau and Beland, 2006). Aloe vera gel contains acemannan, which has been identified as the primary polysaccharide (Hamman 2008). It can affect the humoral immune response and cellular immunity (Zhang et al., 2011).The herb is used internally to combat most digestive problems, including constipation, poor appetite, colitis, irritable bowel syndrome as well as, asthma, diabetes, immune system enhancement, peptic ulcers (Pandey and Singh, 2016) .
Major ingredients of Aloe vera include anthraquinones, saccharides, vitamins, enzymes, and low-molecular-weight compounds (Choi and Chung, 2003) which give Aloe vera its anti-inflammatory, immunomodulatory, wound-healing, anti-viral, anti-fungal, anti-tumor, anti-diabetic, and anti-oxidant effects .Studies revealed that properties of Aloe vera, including wound healing, immunomodulatory, and antibacterial properties, may stem from acemannan . Studies performed on the effects of Aloe vera gel and of polysaccharide contained in Aloe vera (acemannan) on the broilers have shown that Aloe vera gel can improve the immune response in broilers (Valle-paraso et al., 2005). Since it is extremely important to avoid using AGP in poultry feed for the purpose of producing healthy foods and maintaining human health, the present paper aims to review effects of Aloe vera as a natural feed additive on broilers.
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. It can be said that the bioactives of Aloe vera could be used as feed supplement to improve feed efficiency in broilers with no deleterious effect on weight gain, carcass yield, abdominal fat levels and internal organs.
Effects on intestinal microflora
Balance of intestinal microflora in broilers is an important factor contributing to improved growth performance and immune response, and anti-bacterial compounds, like herbs, play a significant role in balancing and improving intestinal microflora in chickens. Aloe vera can improve intestinal microflora and its ecosystem in broilers’ intestines by increasing Lactobacillus count and decreased E. coli count. Although the exact mechanism through which Aloe vera affects intestinal microflora in broilers is unknown, it is likely that this effect is similar to the anti-bacterial effects of some herbs and mushrooms that improve intestinal microflora. On the other hand, 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 .
Effect on carcass characteristics
Darabighane et al. (2011) concluded that the groups treated by Aloe vera gel showed heavier dressing percentage compared to the control group. Singh et al. (2013) concluded that Aloe vera has potential to be a growth promoter in broiler chicks and its growth promoting effects are comparable to that of antibiotic growth promoter (AGP). Eevuri and Putturu (2013) found that Aloe vera supplementation in broilers reduced the fat accumulation, increased dressing percentage, liver weight, spleen weight and whole giblet weights.
Effect on haemato- biochemical parameters
Eevuri and Putturu (2013) found that Aloe vera supplementation in broilers significantly reduced the serum cholesterol, serum triglycerides and increased the humoral response against NCD vaccine. Darabighane et al. (2011) reported an increase in total white blood cell count of broilers as a result of adding Aloe vera gel to broiler feeds. In another study that used Aloe vera gel powder in broiler feeds, a significant increase was observed in total white blood cell count, red blood cell count, and haemoglobin in groups treated with Aloe vera gel powder compared to the control group, with the 1% Aloe vera gel powder group showing the highest haemoglobin, red blood cell, and white blood cell count (Mahdavi et al., 2012).
Effects on immune response
Improved or reinforced immune response in poultry creates resistance against diseases, and health of a flock, which can be the result of preparedness of immune system against pathogenic agents, is an important factor in improving homogeneity, long life, and growth performance of birds. 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 .Acemannan contained in Aloe vera gel is a β (1-4)-linked acetylated mannan containing mannose that can attach to mannose receptors in macrophages and activate these macrophages. In addition, acemannan can stimulate production of cytokines, release of nitric oxide.
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. 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. 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.
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Authors- Sagarika Barman 1, Pompi R Boro 2 and Dibakar Baruah 3
- Research Fellow, College of Veterianary Science,
- KhanaparaPhD Scholar, College of Veterianary Science,
- KhanaparaVeterianary Officer, Demow, Sivasagar